Provided by: ksh_93u+20120801-2ubuntu0.16.04.1_amd64 bug

NAME

       ksh,  rksh,  ksh93,  rksh93  -  KornShell,  a  standard/restricted command and programming
       language

SYNOPSIS

       ksh [ ±abcefhikmnoprstuvxBCDP ] [ -R file ] [ ±o option ] ... [ - ] [ arg ... ]
       rksh [ ±abcefhikmnoprstuvxBCD ] [ -R file ] [ ±o option ] ...  [ - ] [ arg ... ]

DESCRIPTION

       Ksh is a command and programming language that executes commands read from a terminal or a
       file.   Rksh  is  a restricted version of the command interpreter ksh; command interpreter
       ksh; See Invocation below for the meaning of arguments to the shell.

   Definitions.
       A metacharacter is one of the following characters:

              ;   &   (   )      <   >   new-line   space   tab

       A blank is a tab or a  space.   An  identifier  is  a  sequence  of  letters,  digits,  or
       underscores  starting  with a letter or underscore.  Identifiers are used as components of
       variable names.  A vname is a sequence of one or more identifiers separated  by  a  .  and
       optionally  preceded by a ..  Vnames are used as function and variable names.  A word is a
       sequence of characters from the character set defined by  the  current  locale,  excluding
       non-quoted metacharacters.

       A  command  is  a  sequence  of characters in the syntax of the shell language.  The shell
       reads each command and carries out the desired  action  either  directly  or  by  invoking
       separate  utilities.   A  built-in  command  is a command that is carried out by the shell
       itself without creating a  separate  process.   Some  commands  are  built-in  purely  for
       convenience  and  are not documented here.  Built-ins that cause side effects in the shell
       environment and built-ins that are found before performing a path  search  (see  Execution
       below)  are  documented  here.   For  historical  reasons,  some of these built-ins behave
       differently than other built-ins and are called special built-ins.

   Commands.
       A simple-command is a list of variable assignments (see Variable Assignments below)  or  a
       sequence  of blank separated words which may be preceded by a list of variable assignments
       (see Environment below).  The first word specifies the name of the command to be executed.
       Except  as  specified  below,  the  remaining words are passed as arguments to the invoked
       command.  The command name is passed as argument 0 (see exec(2)).  The value of a  simple-
       command  is  its exit status; 0-255 if it terminates normally; 256+signum if it terminates
       abnormally (the name of the signal corresponding to the exit status can  be  obtained  via
       the -l option of the kill built-in utility).

       A  pipeline  is a sequence of one or more commands separated by .  The standard output of
       each command but the last is connected by a pipe(2) to the  standard  input  of  the  next
       command.   Each command, except possibly the last, is run as a separate process; the shell
       waits for the last command to terminate.  The exit status of a pipeline is the exit status
       of  the last command unless the pipefail option is enabled.  Each pipeline can be preceded
       by the reserved word !  which causes the exit status of the pipeline to become  0  if  the
       exit  status of the last command is non-zero, and 1 if the exit status of the last command
       is 0.

       A list is a sequence of one or more pipelines separated by  ;,  &,  ⎪&,  &&,  or  ⎪⎪,  and
       optionally  terminated  by  ;,  &,  or ⎪&.  Of these five symbols, ;, &, and ⎪& have equal
       precedence, which is lower than that of && and ⎪⎪.  The symbols && and ⎪⎪ also have  equal
       precedence.   A  semicolon  (;)  causes sequential execution of the preceding pipeline; an
       ampersand (&) causes asynchronous execution of the preceding  pipeline  (i.e.,  the  shell
       does  not  wait for that pipeline to finish).  The symbol ⎪& causes asynchronous execution
       of the preceding pipeline with a  two-way  pipe  established  to  the  parent  shell;  the
       standard  input  and output of the spawned pipeline can be written to and read from by the
       parent shell by applying the redirection operators <& and >& with arg p to commands and by
       using  -p  option  of the built-in commands read and print described later.  The symbol &&
       (⎪⎪) causes the list following it to be executed only if the preceding pipeline returns  a
       zero (non-zero) value.  One or more new-lines may appear in a list instead of a semicolon,
       to delimit a command.  The first item  of the first pipeline of a list that  is  a  simple
       command  not  beginning with a redirection, and not occurring within a while, until, or if
       list, can be preceded by a semicolon.  This semicolon is ignored unless the showme  option
       is enabled as described with the set built-in below.

       A  command  is  either a simple-command or one of the following.  Unless otherwise stated,
       the value returned by a command is  that  of  the  last  simple-command  executed  in  the
       command.

       for vname [ in word ... ] ;do list ;done
              Each  time  a for command is executed, vname is set to the next word taken from the
              in word list.  If in word ...  is omitted, then the for  command  executes  the  do
              list  once for each positional parameter that is set starting from 1 (see Parameter
              Expansion below).  Execution ends when there are no more words in the list.

       for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
              The arithmetic expression expr1  is  evaluated  first  (see  Arithmetic  evaluation
              below).  The arithmetic expression expr2 is repeatedly evaluated until it evaluates
              to zero and when non-zero, list is executed and  the  arithmetic  expression  expr3
              evaluated.  If any expression is omitted, then it behaves as if it evaluated to 1.

       select vname [ in word ... ] ;do list ;done
              A  select  command  prints  on standard error (file descriptor 2) the set of words,
              each preceded by a number.  If  in  word  ...   is  omitted,  then  the  positional
              parameters  starting  from 1 are used instead (see Parameter Expansion below).  The
              PS3 prompt is printed and a line is read from the standard  input.   If  this  line
              consists  of  the number of one of the listed words, then the value of the variable
              vname is set to the word corresponding to this number.  If this line is empty,  the
              selection  list is printed again.  Otherwise the value of the variable vname is set
              to null.  The contents of the line  read  from  standard  input  is  saved  in  the
              variable  REPLY.   The list is executed for each selection until a break or end-of-
              file is encountered.  If the REPLY variable is set to  null  by  the  execution  of
              list,  then  the selection list is printed before displaying the PS3 prompt for the
              next selection.

       case word in [ [(]pattern [ ⎪ pattern ] ... ) list ;; ] ... esac
              A case command executes the list associated with the  first  pattern  that  matches
              word.   The  form of the patterns is the same as that used for file-name generation
              (see File Name Generation below).  The ;; operator  causes  execution  of  case  to
              terminate.   If  ;&  is  used  in place of ;; the next subsequent list, if any,  is
              executed.

       if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
              The list following if is executed and, if it returns a zero exit status,  the  list
              following  the  first  then  is  executed.   Otherwise,  the list following elif is
              executed and, if its value is zero, the list following the next then  is  executed.
              Failing  each  successive elif list, the else list is executed.  If the if list has
              non-zero exit status and there is no else list, then the if command returns a  zero
              exit status.

       while list ;do list ;done
       until list ;do list ;done
              A  while  command repeatedly executes the while list and, if the exit status of the
              last command in the list  is  zero,  executes  the  do  list;  otherwise  the  loop
              terminates.   If  no  commands  in the do list are executed, then the while command
              returns a zero exit status; until may be used in place of while to negate the  loop
              termination test.

       ((expression))
              The  expression  is  evaluated  using the rules for arithmetic evaluation described
              below.  If the value of the arithmetic expression is non-zero, the exit  status  is
              0, otherwise the exit status is 1.

       (list)
              Execute  list  in  a  separate  environment.   Note,  that  if  two  adjacent  open
              parentheses are needed for nesting, a space must be inserted to avoid evaluation as
              an arithmetic command as described above.

       { list;}
              list  is simply executed.  Note that unlike the metacharacters ( and ), { and } are
              reserved words and must occur at the beginning of a line or after a ; in  order  to
              be recognized.

       [[ expression ]]
              Evaluates  expression  and returns a zero exit status when expression is true.  See
              Conditional Expressions below, for a description of expression.

       function varname { list ;}
       varname () { list ;}
              Define a function which  is  referenced  by  varname.   A  function  whose  varname
              contains  a  .   is  called  a  discipline  function and the portion of the varname
              preceding the last .  must refer to an existing variable.  The body of the function
              is  the  list  of  commands  between { and }.  A function defined with the function
              varname syntax can also be used as an argument to the .  special  built-in  command
              to  get  the equivalent behavior as if the varname() syntax were used to define it.
              (See Functions below.)

       namespace identifier { list ;}
              Defines or uses the name space identifier and runs the commands  in  list  in  this
              name space.  (See Name Spaces below.)

       & [ name [ arg... ]  ]
              Causes  subsequent list commands terminated by & to be placed in the background job
              pool name.  If name is omitted a default unnamed pool is used.  Commands in a named
              background pool may be executed remotely.

       time [ pipeline ]
              If pipeline is omitted the user and system time for the current shell and completed
              child processes is printed on standard error.  Otherwise, pipeline is executed  and
              the elapsed time as well as the user and system time are printed on standard error.
              The TIMEFORMAT variable may be set to a format string that specifies how the timing
              information  should  be  displayed.  See Shell Variables below for a description of
              the TIMEFORMAT variable.

       The following reserved words are recognized as reserved only when they are the first  word
       of a command and are not quoted:

       if then else elif fi case esac for while until do done { } function select time [[ ]] !

   Variable Assignments.
       One  or  more  variable  assignments can start a simple command or can be arguments to the
       typeset, enum, export,  or  readonly  special  built-in  commands  as  well  as  to  other
       declaration commands created as types.  The syntax for an assignment is of the form:

       varname=word
       varname[word]=word
              No space is permitted between varname and the = or between = and word.

       varname=(assign_list)
              No  space  is  permitted  between varname and the =.  The variable varname is unset
              before the assignment.  An assign_list can be one of the following:
                      word ...
                             Indexed array assignment.
                      [word]=word ...
                             Associative array assignment.  If preceded by typeset -a  this  will
                             create an indexed array instead.
                      assignment ...
                             Compound  variable  assignment.   This  creates  a compound variable
                             varname with sub-variables of the form varname.name, where  name  is
                             the  name  portion of assignment.  The value of varname will contain
                             all the assignment elements.  Additional assignments  made  to  sub-
                             variables  of varname will also be displayed as part of the value of
                             varname.  If  no  assignments  are  specified,  varname  will  be  a
                             compound variable allowing subsequence child elements to be defined.
                      typeset [options] assignment ...
                             Nested  variable  assignment.  Multiple assignments can be specified
                             by separating each of them with a ;.  The previous  value  is  unset
                             before the assignment.  Other declaration commands such as readonly,
                             enum, and other  declaration  commands  can  be  used  in  place  of
                             typeset.
                      . filename
                             Include the assignment commands contained in filename.

       In  addition,  a += can be used in place of the = to signify adding to or appending to the
       previous value.  When += is applied to  an  arithmetic  type,  word  is  evaluated  as  an
       arithmetic  expression and added to the current value.  When applied to a string variable,
       the value defined by word is  appended  to  the  value.   For  compound  assignments,  the
       previous  value  is not unset and the new values are appended to the current ones provided
       that the types are compatible.

       The right hand side of a variable assignment undergoes  all  the  expansion  listed  below
       except word splitting, brace expansion, and file name generation.  When the left hand side
       is an assignment is a compound variable and the right hand  is  the  name  of  a  compound
       variable,  the  compound  variable on the right will be copied or appended to the compound
       variable on the left.

   Comments.
       A word beginning with # causes that word and all the following characters up to a new-line
       to be ignored.
   Aliasing.
       The  first  word  of each command is replaced by the text of an alias if an alias for this
       word has been defined.  An alias name consists  of  any  number  of  characters  excluding
       metacharacters,  quoting  characters,  file  expansion characters, parameter expansion and
       command substitution characters, the characters /  and  =.   The  replacement  string  can
       contain  any valid shell script including the metacharacters listed above.  The first word
       of each command in the replaced text, other than any that are  in  the  process  of  being
       replaced, will be tested for aliases.  If the last character of the alias value is a blank
       then the word following the alias will also be checked for  alias  substitution.   Aliases
       can  be  used  to  redefine  built-in commands but cannot be used to redefine the reserved
       words listed above.  Aliases can be created and listed with the alias command and  can  be
       removed with the unalias command.
       Aliasing  is performed when scripts are read, not while they are executed.  Therefore, for
       an alias to take effect, the alias definition  command  has  to  be  executed  before  the
       command which references the alias is read.
       The following aliases are compiled into the shell but can be unset or redefined:
                           autoload=′typeset -fu′
                           command=′command  
                           compound=′typeset -C′
                           fc=hist
                           float=′typeset -lE′
                           functions=′typeset -f′
                           hash=′alias -t --′
                           history=′hist -l′
                           integer=′typeset -li′
                           nameref=′typeset -n′
                           nohup=′nohup  
                           r=′hist -s′
                           redirect=′command exec′
                           source=′command .′
                           stop=′kill -s STOP′
                           suspend=′kill -s STOP $$′
                           times=′{ { time;} 2>&1;}′
                           type=′whence -v′

   Tilde Substitution.
       After  alias  substitution  is performed, each word is checked to see if it begins with an
       unquoted .  For tilde substitution, word also refers to the  word  portion  of  parameter
       expansion (see Parameter Expansion below).  If it does, then the word up to a / is checked
       to see if it matches a user name in the password database (See getpwname(3).)  If a  match
       is  found,  the    and  the matched login name are replaced by the login directory of the
       matched user.  If no match is found, the original text is left unchanged.  A  by  itself,
       or  in  front  of  a /, is replaced by $HOME.  A  followed by a + or - is replaced by the
       value of $PWD and $OLDPWD respectively.

       In addition, when expanding a variable assignment, tilde substitution  is  attempted  when
       the  value  of the assignment begins with a , and when a  appears after a :.  The : also
       terminates a  login name.

   Command Substitution.
       The standard output from a command list enclosed in parentheses preceded by a dollar  sign
       (  $(list) ), or in a brace group preceded by a dollar sign ( ${ list;} ), or in a pair of
       grave accents (``) may be used as part or all of a word; trailing new-lines  are  removed.
       In the second case, the { and } are treated as a reserved words so that { must be followed
       by a blank and } must appear at the beginning of the line or follow a  ;.   In  the  third
       (obsolete) form, the string between the quotes is processed for special quoting characters
       before the command is executed (see Quoting below).  The command substitution $(cat  file)
       can  be  replaced  by the equivalent but faster $(<file).  The command substitution $(n<#)
       will expand to the current byte offset for file descriptor n.  Except for the second form,
       the  command  list  is  run  in  a subshell so that no side effects are possible.  For the
       second form, the final } will be recognized as a reserved word after any token.

   Arithmetic Substitution.
       An arithmetic expression enclosed in double parentheses preceded by a dollar sign (  $(())
       ) is replaced by the value of the arithmetic expression within the double parentheses.

   Process Substitution.
       Each  command argument of the form <(list) or >(list) will run process list asynchronously
       connected to some file in /dev/fd if this directory exists, or else  a  fifo  a  temporary
       directory.   The  name  of this file will become the argument to the command.  If the form
       with > is selected then writing on this file will provide input for list.  If <  is  used,
       then  the  file  passed  as  an argument will contain the output of the list process.  For
       example,

              paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1) >(process2)

       cuts fields 1 and 3 from the files  file1  and  file2  respectively,  pastes  the  results
       together,  and sends it to the processes process1 and process2, as well as putting it onto
       the standard output.  Note that the file, which is passed as an argument to  the  command,
       is a UNIX pipe(2) so programs that expect to lseek(2) on the file will not work.

       Process  substitution of the form <(list) can also be used with the < redirection operator
       which causes the output of list to be standard  input  or  the  input  for  whatever  file
       descriptor is specified.

   Parameter Expansion.
       A  parameter is a variable, one or more digits, or any of the characters , @, #, ?, -, $,
       and !.  A variable is denoted by a vname.  To create a variable whose vname contains a  .,
       a  variable  whose  vname  consists of everything before the last . must already exist.  A
       variable has a value and zero or more attributes.  Variables can be  assigned  values  and
       attributes by using the typeset special built-in command.  The attributes supported by the
       shell are described later with the typeset special built-in command.   Exported  variables
       pass values and attributes to the environment.

       The  shell  supports both indexed and associative arrays.  An element of an array variable
       is referenced by a subscript.   A  subscript  for  an  indexed  array  is  denoted  by  an
       arithmetic  expression  (see  Arithmetic evaluation below) between a [ and a ].  To assign
       values to an indexed array, use vname=(value ...) or set -A vname  value ... .  The  value
       of  all  non-negative  subscripts must be in the range of 0 through 4,194,303.  A negative
       subscript is treated as an offset from the maximum current index +1 so that -1  refers  to
       the  last element.  Indexed arrays can be declared with the -a option to typeset.  Indexed
       arrays need not be declared.  Any reference to a variable with a valid subscript is  legal
       and an array will be created if necessary.

       An  associative  array  is  created  with  the  -A  option to typeset.  A subscript for an
       associative array is denoted by a string enclosed between [ and ].

       Referencing any array without a subscript is equivalent  to  referencing  the  array  with
       subscript 0.

       The value of a variable may be assigned by writing:

              vname=value [ vname=value ] ...

       or
              vname[subscript]=value [ vname[subscript]=value ] ...
       Note that no space is allowed before or after the =.
       Attributes  assigned  by the typeset special built-in command apply to all elements of the
       array.  An array element can be a  simple  variable,  a  compound  variable  or  an  array
       variable.  An element of an indexed array can be either an indexed array or an associative
       array.  An element of an associative array can also be  either.   To  refer  to  an  array
       element  that  is  part  of  an array element, concatenate the subscript in brackets.  For
       example, to refer to the foobar element of an associative array that  is  defined  as  the
       third element of the indexed array, use ${vname[3][foobar]}
       A  nameref  is  a  variable that is a reference to another variable.  A nameref is created
       with the -n attribute of typeset.  The value of the variable at the time  of  the  typeset
       command  becomes  the  variable  that  will be referenced whenever the nameref variable is
       used.  The name of a nameref cannot contain  a  ..   When  a  variable  or  function  name
       contains a ., and the portion of the name up to the first . matches the name of a nameref,
       the variable referred to is obtained by replacing the nameref portion with the name of the
       variable  referenced  by  the nameref.  If a nameref is used as the index of a for loop, a
       name reference is established for each item in the list.  A nameref provides a  convenient
       way  to  refer  to the variable inside a function whose name is passed as an argument to a
       function.  For example, if the name of a variable is passed as the  first  argument  to  a
       function, the command
              typeset -n var=$1
       inside  the  function  causes  references  and  assignments  to  var  to be references and
       assignments to the variable whose name has been passed to the function.
       If any of the floating point attributes, -E, -F, or -X, or the integer attribute,  -i,  is
       set for vname, then the value is subject to arithmetic evaluation as described below.
       Positional parameters, parameters denoted by a number, may be assigned values with the set
       special built-in command.  Parameter $0 is set  from  argument  zero  when  the  shell  is
       invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
              The  shell  reads  all the characters from ${ to the matching } as part of the same
              word even if it contains braces or metacharacters.   The  value,  if  any,  of  the
              parameter  is substituted.  The braces are required when parameter is followed by a
              letter, digit, or underscore that is not to be interpreted as  part  of  its  name,
              when  the variable name contains a ..  The braces are also required when a variable
              is subscripted unless it is part of  an  Arithmetic  Expression  or  a  Conditional
              Expression.   If parameter is one or more digits then it is a positional parameter.
              A positional parameter of more than one digit  must  be  enclosed  in  braces.   If
              parameter  is    or  @,  then all the positional parameters, starting with $1, are
              substituted (separated by a field separator character).  If  an  array  vname  with
              last  subscript   @, or for index arrays of the form sub1 ..  sub2.  is used, then
              the value for each of the elements between sub1 and sub2 inclusive (or all elements
              for  and @) is substituted, separated by the first character of the value of IFS.
       ${#parameter}
              If  parameter  is    or  @,  the  number  of positional parameters is substituted.
              Otherwise, the length of the value of the parameter is substituted.
       ${#vname[*]}
       ${#vname[@]}
              The number of elements in the array vname is substituted.

       ${@vname}
              Expands to the type name (See Type Variables  below) or attributes of the  variable
              referred to by vname.
       ${!vname}
              Expands  to  the  name  of  the  variable referred to by vname.  This will be vname
              except when vname is a name reference.
       ${!vname[subscript]}
              Expands to name of the subscript unless subscript is *, @.  or of the form sub1  ..
              sub2.   When  subscript  is *, the list of array subscripts for vname is generated.
              For a variable that is not an array, the  value  is  0  if  the  variable  is  set.
              Otherwise it is null.  When subscript is @, same as above, except that when used in
              double quotes, each array subscript yields a separate argument.  When subscript  is
              of  the  form  sub1  ..  sub2 it expands to the list of subscripts between sub1 and
              sub2 inclusive using the same quoting rules as @.
       ${!prefix*}
              Expands to the names of the variables whose names begin with prefix.
       ${parameter:-word}
              If parameter is set and is non-null then substitute its value; otherwise substitute
              word.
       ${parameter:=word}
              If  parameter is not set or is null then set it to word; the value of the parameter
              is then substituted.  Positional parameters may not be assigned to in this way.
       ${parameter:?word}
              If parameter is set and is non-null then substitute  its  value;  otherwise,  print
              word  and  exit  from  the  shell  (if not interactive).  If word is omitted then a
              standard message is printed.
       ${parameter:+word}
              If parameter is set and is non-null  then  substitute  word;  otherwise  substitute
              nothing.
       In  the above, word is not evaluated unless it is to be used as the substituted string, so
       that, in the following example, pwd is executed only if d is not set or is null:
              print ${d:-$(pwd)}
       If the colon ( : ) is omitted from the above  expressions,  then  the  shell  only  checks
       whether parameter is set or not.
       ${parameter:offset:length}
       ${parameter:offset}
              Expands  to  the  portion  of  the  value  of  parameter  starting at the character
              (counting from 0) determined by expanding offset as an  arithmetic  expression  and
              consisting  of  the  number  of  characters determined by the arithmetic expression
              defined by length.  In the second form, the remainder of the value is used.   If  A
              negative  offset counts backwards from the end of parameter.  Note that one or more
              blanks is required in front of a minus sign to prevent the shell from  interpreting
              the operator as :-.  If parameter is  or @, or is an array name indexed by  or @,
              then  offset  and  length  refer  to  the  array  index  and  number  of   elements
              respectively.   A negative offset is taken relative to one greater than the highest
              subscript for indexed arrays.  The order for associate arrays is unspecified.
       ${parameter#pattern}
       ${parameter##pattern}
              If the shell pattern matches the beginning of the  value  of  parameter,  then  the
              value  of  this  expansion  is  the value of the parameter with the matched portion
              deleted; otherwise the value of this parameter is substituted.  In the  first  form
              the  smallest  matching  pattern  is  deleted  and  in  the second form the largest
              matching pattern is deleted.  When parameter is @, *, or  an  array  variable  with
              subscript @ or *, the substring operation is applied to each element in turn.

       ${parameter%pattern}
       ${parameter%%pattern}
              If  the  shell pattern matches the end of the value of parameter, then the value of
              this expansion is the value  of  the  parameter  with  the  matched  part  deleted;
              otherwise  substitute  the  value  of  parameter.   In  the first form the smallest
              matching pattern is deleted and in the second form the largest matching pattern  is
              deleted.   When  parameter is @, *, or an array variable with subscript @ or *, the
              substring operation is applied to each element in turn.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
       ${parameter/#pattern/string}
       ${parameter/%pattern/string}
              Expands parameter and replaces the longest match of pattern with the given  string.
              Each  occurrence  of  \n  in  string  is  replaced by the portion of parameter that
              matches the n-th sub-pattern.  In the first form,  only  the  first  occurrence  of
              pattern is replaced.  In the second form, each match for pattern is replaced by the
              given string.  The third form restricts the pattern match to the beginning  of  the
              string  while the fourth form restricts the pattern match to the end of the string.
              When string is null, the pattern will be deleted and the / in front of  string  may
              be  omitted.   When  parameter is @, *, or an array variable with subscript @ or *,
              the substitution operation is applied to each element in turn.  In this  case,  the
              string portion of word will be re-evaluated for each element.

       The following parameters are automatically set by the shell:
              #      The number of positional parameters in decimal.
              -      Options supplied to the shell on invocation or by the set command.
              ?      The decimal value returned by the last executed command.
              $      The process number of this shell.
              _      Initially,  the  value  of  _ is an absolute pathname of the shell or script
                     being executed as passed in the environment.  Subsequently  it  is  assigned
                     the  last  argument  of the previous command.  This parameter is not set for
                     commands which are asynchronous.  This parameter is also used  to  hold  the
                     name  of  the  matching  MAIL file when checking for mail.  While defining a
                     compound variable or a type, _ is initialized as a reference to the compound
                     variable  or  type.  When a discipline function is invoked, _ is initialized
                     as a reference to the variable associated with the call  to  this  function.
                     Finally  when  _  is  used  as  the  name  of  the  first variable of a type
                     definition, the new type is derived from the type of the first variable (See
                     Type Variables  below.).
              !      The  process  id  or  the  pool  name  and job number of the last background
                     command invoked or the most recent job put in the  background  with  the  bg
                     built-in  command.   Background  jobs started in a named pool will be in the
                     form pool.number where pool is the pool name and number is  the  job  number
                     within that pool.
              .sh.command
                     When  processing  a  DEBUG  trap, this variable contains the current command
                     line that is about to run.
              .sh.edchar
                     This variable contains the value of the keyboard character (or  sequence  of
                     characters  if  the  first  character  is  an  ESC, ascii 033) that has been
                     entered when processing a KEYBD trap (see Key Bindings below).  If the value
                     is  changed  as part of the trap action, then the new value replaces the key
                     (or key sequence) that caused the trap.
              .sh.edcol
                     The character position of the cursor at the time of the  most  recent  KEYBD
                     trap.
              .sh.edmode
                     The  value  is  set  to  ESC when processing a KEYBD trap while in vi insert
                     mode.  (See Vi Editing Mode  below.)  Otherwise,  .sh.edmode  is  null  when
                     processing a KEYBD trap.
              .sh.edtext
                     The  characters  in  the  input  buffer at the time of the most recent KEYBD
                     trap.  The value is null when not processing a KEYBD trap.
              .sh.file
                     The pathname of the file than contains the current command.
              .sh.fun
                     The name of the current function that is being executed.
              .sh.level
                     Set to the current function depth.  This can be changed inside a DEBUG  trap
                     and will set the context to the specified level.
              .sh.lineno
                     Set during a DEBUG trap to the line number for the caller of each function.
              .sh.match
                     An  indexed array which stores the most recent match and sub-pattern matches
                     after conditional pattern matches that match and after variables  expansions
                     using  the operators #, %, or /.  The 0-th element stores the complete match
                     and the i-th.  element stores the i-th  submatch.   The  .sh.match  variable
                     becomes unset when the variable that has expanded is assigned a new value.
              .sh.math
                     Used  for  defining  arithmetic functions (see Arithmetic evaluation below).
                     and stores the list of user defined arithmetic functions.
              .sh.name
                     Set to the name of the variable at the time that a  discipline  function  is
                     invoked.
              .sh.subscript
                     Set  to  the  name  subscript  of the variable at the time that a discipline
                     function is invoked.
              .sh.subshell
                     The current depth for subshells and command substitution.
              .sh.value
                     Set to the value of the  variable  at  the  time  that  the  set  or  append
                     discipline  function is invoked.  When a user defined arithmetic function is
                     invoked, the value of .sh.value is saved and .sh.value is set to long double
                     precision floating point.  .sh.value is restored when the function returns.
              .sh.version
                     Set to a value that identifies the version of this shell.
              KSH_VERSION
                     A name reference to .sh.version.
              LINENO The current line number within the script or function being executed.
              OLDPWD The previous working directory set by the cd command.
              OPTARG The  value  of  the  last  option argument processed by the getopts built-in
                     command.
              OPTIND The index of the last option argument  processed  by  the  getopts  built-in
                     command.
              PPID   The process number of the parent of the shell.
              PWD    The present working directory set by the cd command.
              RANDOM Each   time  this  variable  is  referenced,  a  random  integer,  uniformly
                     distributed between 0 and 32767,  is  generated.   The  sequence  of  random
                     numbers can be initialized by assigning a numeric value to RANDOM.
              REPLY  This  variable  is  set  by  the  select  statement and by the read built-in
                     command when no arguments are supplied.
              SECONDS
                     Each time this variable is referenced, the number  of  seconds  since  shell
                     invocation  is  returned.   If  this  variable is assigned a value, then the
                     value returned upon reference will be the value that was assigned  plus  the
                     number of seconds since the assignment.
              SHLVL  An integer variable the is incremented each time the shell is invoked and is
                     exported.  If SHLVL is not in the environment when the shell is invoked,  it
                     is set to 1.

       The following variables are used by the shell:
              CDPATH The search path for the cd command.
              COLUMNS
                     If  this  variable is set, the value is used to define the width of the edit
                     window for the shell edit modes and for printing select lists.
              EDITOR If the VISUAL variable is not set,  the  value  of  this  variable  will  be
                     checked   for   the   patterns  as  described  with  VISUAL  below  and  the
                     corresponding editing option (see Special Command set below) will be  turned
                     on.
              ENV    If this variable is set, then parameter expansion, command substitution, and
                     arithmetic substitution are performed on the value to generate the  pathname
                     of  the script that will be executed when the shell is invoked interactively
                     (see Invocation below).  This file is typically used for alias and  function
                     definitions.   The default value is $HOME/.kshrc.  On systems that support a
                     system wide  /etc/ksh.kshrc initialization file, if the  filename  generated
                     by   the  expansion  of  ENV  begins  with  /./  or  ././  the  system  wide
                     initialization file will not be executed.
              FCEDIT Obsolete name for the default editor name for the hist command.   FCEDIT  is
                     not used when HISTEDIT is set.
              FIGNORE
                     A  pattern  that  defines  the  set  of  filenames that will be ignored when
                     performing filename matching.
              FPATH  The search path for function definitions.  The directories in this path  are
                     searched  for  a  file  with the same name as the function or command when a
                     function with the -u attribute is referenced  and  when  a  command  is  not
                     found.   If  an executable file with the name of that command is found, then
                     it is read and executed  in  the  current  environment.   Unlike  PATH,  the
                     current  directory  must  be  represented  explicitly  by  .  rather than by
                     adjacent : characters or a beginning or ending :.
              HISTCMD
                     Number of the current command in the history file.
              HISTEDIT
                     Name for the default editor name for the hist command.
              HISTFILE
                     If this variable is set when the shell is invoked, then  the  value  is  the
                     pathname  of  the  file  that will be used to store the command history (see
                     Command Re-entry below).
              HISTSIZE
                     If this variable is set when the  shell  is  invoked,  then  the  number  of
                     previously  entered  commands  that  are  accessible  by  this shell will be
                     greater than or equal to this number.  The default is 512.
              HOME   The default argument (home directory) for the cd command.
              IFS    Internal field separators, normally space, tab, and new-line that  are  used
                     to  separate  the results of command substitution or parameter expansion and
                     to separate fields with the built-in command read.  The first  character  of
                     the  IFS  variable  is  used to separate arguments for the "$∗" substitution
                     (see Quoting below).  Each single occurrence of  an  IFS  character  in  the
                     string  to  be  split,  that  is not in the isspace character class, and any
                     adjacent characters in IFS that are in the isspace character class,  delimit
                     a field.  One or more characters in IFS that belong to the isspace character
                     class, delimit a field.  In addition, if the same isspace character  appears
                     consecutively inside IFS, this character is treated as if it were not in the
                     isspace class, so that if IFS consists  of  two  tab  characters,  then  two
                     adjacent tab characters delimit a null field.
              JOBMAX This  variable  defines  the maximum number running background jobs that can
                     run at a time.  When this limit is reached, the shell will wait for a job to
                     complete before staring a new job.
              LANG   This   variable   determines  the  locale  category  for  any  category  not
                     specifically selected with a variable starting with LC_ or LANG.
              LC_ALL This variable overrides the value of the LANG variable  and  any  other  LC_
                     variable.
              LC_COLLATE
                     This  variable  determines  the  locale  category  for  character  collation
                     information.
              LC_CTYPE
                     This  variable  determines  the  locale  category  for  character   handling
                     functions.   It  determines  the character classes for pattern matching (see
                     File Name Generation below).
              LC_NUMERIC
                     This  variable  determines  the  locale  category  for  the  decimal   point
                     character.
              LINES  If  this  variable  is set, the value is used to determine the column length
                     for printing select lists.  Select lists will print vertically  until  about
                     two-thirds of LINES lines are filled.
              MAIL   If this variable is set to the name of a mail file and the MAILPATH variable
                     is not set, then the shell informs the  user  of  arrival  of  mail  in  the
                     specified file.
              MAILCHECK
                     This  variable  specifies  how  often  (in seconds) the shell will check for
                     changes in the modification time of  any  of  the  files  specified  by  the
                     MAILPATH  or  MAIL  variables.   The default value is 600 seconds.  When the
                     time has elapsed the shell will check before issuing the next prompt.
              MAILPATH
                     A colon ( : ) separated list of file names.  If this variable is  set,  then
                     the  shell informs the user of any modifications to the specified files that
                     have occurred within the last MAILCHECK seconds.   Each  file  name  can  be
                     followed  by  a  ?   and  a  message that will be printed.  The message will
                     undergo  parameter   expansion,   command   substitution,   and   arithmetic
                     substitution  with  the variable $_ defined as the name of the file that has
                     changed.  The default message is you have mail in $_.
              PATH   The search path for commands (see Execution below).  The user may not change
                     PATH if executing under rksh (except in .profile).
              PS1    The  value  of  this  variable  is expanded for parameter expansion, command
                     substitution, and arithmetic  substitution  to  define  the  primary  prompt
                     string  which  by  default is ``$''.  The character !  in the primary prompt
                     string is replaced by the command number (see Command Re-entry below).   Two
                     successive occurrences of !  will produce a single !  when the prompt string
                     is printed.
              PS2    Secondary prompt string, by default ``> ''.
              PS3    Selection prompt string used within a select loop, by default ``#? ''.
              PS4    The value of this variable is expanded  for  parameter  evaluation,  command
                     substitution,  and  arithmetic  substitution  and  precedes  each line of an
                     execution trace.  By default, PS4 is ``+ ''.  In addition when PS4 is unset,
                     the execution trace prompt is also ``+ ''.
              SHELL  The pathname of the shell is kept in the environment.  At invocation, if the
                     basename of this variable is rsh, rksh, or  krsh,  then  the  shell  becomes
                     restricted.
              TIMEFORMAT
                     The  value  of  this parameter is used as a format string specifying how the
                     timing information for pipelines prefixed with the time reserved word should
                     be displayed.  The % character introduces a format sequence that is expanded
                     to a time value or  other  information.   The  format  sequences  and  their
                     meanings are as follows.
                     %%        A literal %.
                     %[p][l]R  The elapsed time in seconds.
                     %[p][l]U  The number of CPU seconds spent in user mode.
                     %[p][l]S  The number of CPU seconds spent in system mode.
                     %P        The CPU percentage, computed as (U + S) / R.

                     The brackets denote optional portions.  The optional p is a digit specifying
                     the precision, the number of fractional digits after  a  decimal  point.   A
                     value  of 0 causes no decimal point or fraction to be output.  At most three
                     places after the decimal point can be displayed; values of p greater than  3
                     are treated as 3.  If p is not specified, the value 3 is used.

                     The  optional  l  specifies a longer format, including hours if greater than
                     zero, minutes, and seconds  of  the  form  HHhMMmSS.FFs.   The  value  of  p
                     determines whether or not the fraction is included.

                     All  other  characters  are  output without change and a trailing newline is
                     added.  If unset, the default  value,  $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS',
                     is used.  If the value is null, no timing information is displayed.

              TMOUT  If set to a value greater than zero, TMOUT will be the default timeout value
                     for the read built-in command.  The select compound command terminates after
                     TMOUT  seconds  when  input  is  from a terminal.  Otherwise, the shell will
                     terminate if a line is not entered within the prescribed number  of  seconds
                     while  reading from a terminal.  (Note that the shell can be compiled with a
                     maximum bound for this value which cannot be exceeded.)

              VISUAL If the value of this variable matches the pattern *[Vv][Ii]*,  then  the  vi
                     option  (see  Special Command set below) is turned on.  If the value matches
                     the pattern *gmacs* , the gmacs option is turned on.  If the  value  matches
                     the  pattern  *macs*, then the emacs option will be turned on.  The value of
                     VISUAL overrides the value of EDITOR.

       The shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK, FCEDIT,  TMOUT  and
       IFS,  while  HOME,  SHELL, ENV, and MAIL are not set at all by the shell (although HOME is
       set by login(1)).  On some systems MAIL and SHELL are also set by login(1).

   Field Splitting.
       After parameter expansion and command  substitution,  the  results  of  substitutions  are
       scanned  for  the  field separator characters (those found in IFS) and split into distinct
       fields where such characters are found.  Explicit null fields (""  or  ′′)  are  retained.
       Implicit  null  fields  (those  resulting  from  parameters that have no values or command
       substitutions with no output) are removed.

       If the braceexpand (-B) option is set then each of  the  fields  resulting  from  IFS  are
       checked  to  see  if  they  contain  one  or  more of the brace patterns {*,*}, {l1..l2} ,
       {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} , or {n1..n2 ..n3%fmt} , where *  represents  any
       character, l1,l2 are letters and n1,n2,n3 are signed numbers and fmt is a format specified
       as used by printf.  In each case, fields are created by prepending the  characters  before
       the  {  and  appending  the characters after the } to each of the strings generated by the
       characters between the { and }.  The resulting fields are checked to see if they have  any
       brace patterns.

       In  the  first  form, a field is created for each string between { and ,, between , and ,,
       and between , and }.  The string represented by * can contain embedded matching  {  and  }
       without quoting.  Otherwise, each { and } with * must be quoted.

       In  the  seconds  form,  l1  and  l2  must both be either upper case or both be lower case
       characters in the C locale.  In this case a field is created for each  character  from  l1
       thru l2.

       In  the  remaining forms, a field is created for each number starting at n1 and continuing
       until it reaches n2 incrementing n1 by n3.  The cases where n3 is not specified behave  as
       if  n3  where 1 if n1<=n2 and -1 otherwise.  If forms which specify %fmt any format flags,
       widths and precisions can be specified and fmt can end in any of the  specifiers  cdiouxX.
       For  example,  {a,z}{1..5..3%02d}{b..c}x  expands  to  the  8 fields, a01bx, a01cx, a04bx,
       a04cx, z01bx, z01cx, z04bx and z4cx.

   File Name Generation.
       Following splitting, each field is scanned for the characters , ?, (, and [ unless the -f
       option  has  been set.  If one of these characters appears, then the word is regarded as a
       pattern.  Each file name component that contains any pattern character is replaced with  a
       lexicographically sorted set of names that matches the pattern from that directory.  If no
       file name is found that matches the pattern, then that component of the filename  is  left
       unchanged  unless  the  pattern  is  prefixed  with  ∼(N)  in  which case it is removed as
       described below.  If FIGNORE is set, then  each  file  name  component  that  matches  the
       pattern defined by the value of FIGNORE is ignored when generating the matching filenames.
       The names .  and ..  are also ignored.  If FIGNORE is not set, the  character  .   at  the
       start  of  each  file  name  component  will  be ignored unless the first character of the
       pattern corresponding to this component is the character .  itself.  Note, that for  other
       uses of pattern matching the / and .  are not treated specially.

                    Matches  any  string,  including  the  null  string.  When used for filename
                     expansion, if the globstar option is on, two adjacent  's  by  itself  will
                     match  all  files  and  zero  or  more  directories  and subdirectories.  If
                     followed by a / then only directories and subdirectories will match.
              ?      Matches any single character.
              [...]  Matches any one of the enclosed characters.  A pair of characters  separated
                     by  -  matches  any character lexically between the pair, inclusive.  If the
                     first character following the opening [ is a !  or ^ then any character  not
                     enclosed is matched.  A - can be included in the character set by putting it
                     as the first or last character.
                     Within [ and ], character classes can be specified with the syntax [:class:]
                     where  class is one of the following classes defined in the ANSI-C standard:
                     (Note that word is equivalent to alnum plus the character _.)
                     alnum alpha blank cntrl digit graph  lower  print  punct  space  upper  word
                     xdigit
                     Within  [ and ], an equivalence class can be specified with the syntax [=c=]
                     which matches all characters with the  same  primary  collation  weight  (as
                     defined  by  the  current  locale)  as  the  character  c.   Within [ and ],
                     [.symbol.]  matches the collating symbol symbol.
       A pattern-list is a list of one or more patterns separated from each other with a & or  .
       A  &  signifies that all patterns must be matched whereas  requires that only one pattern
       be matched.  Composite patterns can be formed with one  or  more  of  the  following  sub-
       patterns:
              ?(pattern-list)
                     Optionally matches any one of the given patterns.
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns.
              +(pattern-list)
                     Matches one or more occurrences of the given patterns.
              {n}(pattern-list)
                     Matches n occurrences of the given patterns.
              {m,n}(pattern-list)
                     Matches  from  m to n occurrences of the given patterns.  If m is omitted, 0
                     will be used.  If n is omitted at least m occurrences will be matched.
              @(pattern-list)
                     Matches exactly one of the given patterns.
              !(pattern-list)
                     Matches anything except one of the given patterns.
       By default, each pattern, or sub-pattern will match the longest string possible consistent
       with  generating  the  longest overall match.  If more than one match is possible, the one
       starting closest to the beginning of the string will be chosen.   However, for each of the
       above  compound patterns a - can be inserted in front of the ( to cause the shortest match
       to the specified pattern-list to be used.

       When pattern-list is contained within parentheses, the backslash character  \  is  treated
       specially  even  when  inside  a  character  class.    All  ANSI-C  character  escapes are
       recognized and match the specified character.  In addition the following escape  sequences
       are recognized:
              \d     Matches any character in the digit class.
              \D     Matches any character not in the digit class.
              \s     Matches any character in the space class.
              \S     Matches any character not in the space class.
              \w     Matches any character in the word class.
              \W     Matches any character not in the word class.

       A pattern of the form %(pattern-pair(s)) is a sub-pattern that can be used to match nested
       character expressions.  Each pattern-pair is a two character sequence which cannot contain
       &  or  .   The  first  pattern-pair  specifies the starting and ending characters for the
       match.  Each subsequent pattern-pair represents the beginning and ending characters  of  a
       nested  group  that  will  be  skipped  over  when  counting starting and ending character
       matches.  The behavior is unspecified when the first character of a pattern-pair is alpha-
       numeric except for the following:
              D      Causes the ending character to terminate the search for this pattern without
                     finding a match.
              E      Causes the ending character to be interpreted as an escape character.
              L      Causes the ending character to be interpreted as a quote  character  causing
                     all characters to be ignored when looking for a match.
              Q      Causes  the  ending character to be interpreted as a quote character causing
                     all characters other than any escape character to be  ignored  when  looking
                     for a match.
       Thus,  %({}Q"E\),  matches  characters  starting  at  {  until the matching } is found not
       counting any { or } that is inside a double  quoted  string  or  preceded  by  the  escape
       character \.  Without the {} this pattern matches any C language string.

       Each sub-pattern in a composite pattern is numbered, starting at 1, by the location of the
       ( within the pattern.  The sequence \n, where n is a single digit and \n comes  after  the
       n-th. sub-pattern, matches the same string as the sub-pattern itself.

       Finally  a  pattern  can  contain  sub-patterns of the form ∼(options:pattern-list), where
       either options or :pattern-list can be omitted.  Unlike the other compound patterns, these
       sub-patterns  are not counted in the numbered sub-patterns.  :pattern-list must be omitted
       for options F, G, N , and V below.  If options is present, it can consist of one  or  more
       of the following:
              +      Enable the following options.  This is the default.
              -      Disable the following options.
              E      The  remainder  of  the pattern uses extended regular expression syntax like
                     the egrep(1) command.
              F      The remainder of the pattern uses fgrep(1) expression syntax.
              G      The remainder of the pattern uses basic regular expression syntax  like  the
                     grep(1) command.
              K      The  remainder  of  the  pattern  uses  shell  pattern  syntax.  This is the
                     default.
              N      This is ignored.  However, when it is the first letter and is used with file
                     name generation, and no matches occur, the file pattern expands to the empty
                     string.
              X      The remainder of the pattern uses augmented regular expression  syntax  like
                     the xgrep(1) command.
              P      The  remainder  of  the pattern uses perl(1) regular expression syntax.  Not
                     all perl regular expression syntax is currently implemented.
              V      The remainder of the pattern uses System V regular expression syntax.
              i      Treat the match as case insensitive.
              g      File the longest match (greedy).  This is the default.
              l      Left anchor the pattern.  This is the default for K style patterns.
              r      Right anchor the pattern.  This is the default for K style patterns.
       If both options and :pattern-list are specified, then the options apply only to   pattern-
       list.   Otherwise,  these options remain in effect until they are disabled by a subsequent
       ∼(...) or at the end of the sub-pattern containing ∼(...).

   Quoting.
       Each of the metacharacters listed earlier (see Definitions above) has a special meaning to
       the  shell  and  causes  termination  of  a word unless quoted.  A character may be quoted
       (i.e., made to stand for itself) by preceding it with a \.  The pair \new-line is removed.
       All  characters enclosed between a pair of single quote marks (′′) that is not preceded by
       a $ are quoted.  A single quote cannot appear within the single quotes.  A  single  quoted
       string  preceded  by  an  unquoted  $  is  processed  as  an  ANSI-C string except for the
       following:
       \0     Causes the remainder of the string to be ignored.
       \E     Equivalent to the escape character (ascii 033),
       \e     Equivalent to the escape character (ascii 033),
       \cx    Expands to the character control-x.
       \C[.name.]
              Expands to the collating element name.

       Inside double quote marks (""), parameter and command substitution occur and \ quotes  the
       characters  \, `, ", and $.  A $ in front of a double quoted string will be ignored in the
       "C" or "POSIX" locale, and may cause the string to be replaced by a locale specific string
       otherwise.   The  meaning  of  $∗  and  $@  is identical when not quoted or when used as a
       variable assignment value or as a file name.  However, when used as  a  command  argument,
       "$∗"  is  equivalent  to  "$1d$2d...", where d is the first character of the IFS variable,
       whereas "$@" is equivalent to "$1" "$2" ....  Inside grave quote marks (``), \ quotes  the
       characters  \,  `,  and  $.   If  the grave quotes occur within double quotes, then \ also
       quotes the character ".

       The special meaning of reserved words or aliases can be removed by quoting  any  character
       of  the reserved word.  The recognition of function names or built-in command names listed
       below cannot be altered by quoting them.

   Arithmetic Evaluation.
       The shell performs arithmetic evaluation  for  arithmetic  substitution,  to  evaluate  an
       arithmetic  command,  to evaluate an indexed array subscript, and to evaluate arguments to
       the built-in commands shift and let.  Evaluations are  performed  using  double  precision
       floating point arithmetic or long double precision floating point for systems that provide
       this data type.  Floating point constants follow the ANSI-C programming language  floating
       point  conventions.  The floating point constants Nan and Inf can be use to represent "not
       a number" and infinity respectively.  Integer  constants  follow  the  ANSI-C  programming
       language  integer  constant  conventions although only single byte character constants are
       recognized and character casts are not recognized.  In addition constants can  be  of  the
       form  [base#]n  where base is a decimal number between two and sixty-four representing the
       arithmetic base and n is a number in that base.  The digits above 9 are represented by the
       lower case letters, the upper case letters, @, and _ respectively.  For bases less than or
       equal to 36, upper and lower case characters can be used interchangeably.

       An arithmetic expression uses the same syntax, precedence, and associativity of expression
       as  the  C language.  All the C language operators that apply to floating point quantities
       can be used.  In addition, the operator ** can be used for exponentiation.  It has  higher
       precedence than multiplication and is left associative.  In addition, when the value of an
       arithmetic variable or sub-expression can be represented as a long integer, all C language
       integer  arithmetic  operations  can  be  performed.   Variables can be referenced by name
       within an arithmetic expression without using the  parameter  expansion  syntax.   When  a
       variable is referenced, its value is evaluated as an arithmetic expression.

       Any  of  the  following  math library functions that are in the C math library can be used
       within an arithmetic expression:

       abs acos acosh asin asinh atan atan2 atanh cbrt ceil copysign cos cosh erf erfc  exp  exp2
       expm1  fabs  fpclassify fdim finite floor fma fmax fmin fmod hypot ilogb int isfinite sinf
       isnan isnormal issubnormal issubordered iszero  j0  j1  jn  lgamma  log  log10  log2  logb
       nearbyint  nextafter  nexttoward  pow remainder rint round scanb signbit sin sinh sqrt tan
       tanh tgamma trunc y0 y1 yn In addition,  arithmetic  functions  can  be  define  as  shell
       functions with a variant of the function name syntax,

       function .sh.math.name ident ... { list ;}
              where  name  is  the  function  name  used  in  the  arithmetic expression and each
              identifier, ident is a name reference to the long double precision  floating  point
              argument.   The  value  of .sh.value when the function returns is the value of this
              function.  User defined functions can take up to 3 arguments and  override  C  math
              library functions.

       An  internal  representation  of  a  variable  as a double precision floating point can be
       specified with the -E [n], -F [n], or -X  [n]  option  of  the  typeset  special  built-in
       command.   The  -E  option  causes  the  expansion  of  the  value to be represented using
       scientific notation when it is expanded.  The  optional  option  argument  n  defines  the
       number  of significant figures.  The -F option causes the expansion to be represented as a
       floating decimal number when it is expanded.  The -X option  cause  the  expansion  to  be
       represented  using  the  %a  format  defined  by ISO C-99.  The optional option argument n
       defines the number of places after the decimal (or radix) point in this case.

       An internal integer representation of a variable can be specified with the -i  [n]  option
       of  the  typeset  special  built-in  command.  The optional option argument n specifies an
       arithmetic base to be used when  expanding  the  variable.   If  you  do  not  specify  an
       arithmetic base, base 10 will be used.

       Arithmetic  evaluation is performed on the value of each assignment to a variable with the
       -E, -F, -X, or -i attribute.  Assigning a floating point number to a variable  whose  type
       is an integer causes the fractional part to be truncated.

   Prompting.
       When  used  interactively,  the shell prompts with the value of PS1 after expanding it for
       parameter expansion, command substitution, and arithmetic substitution, before  reading  a
       command.   In addition, each single !  in the prompt is replaced by the command number.  A
       !!  is required to place !  in the prompt.  If at any time a new-line is typed and further
       input  is needed to complete a command, then the secondary prompt (i.e., the value of PS2)
       is issued.

   Conditional Expressions.
       A conditional expression is used with the [[ compound command to test attributes of  files
       and to compare strings.  Field splitting and file name generation are not performed on the
       words between [[ and ]].  Each expression can be constructed  from  one  or  more  of  the
       following unary or binary expressions:
       string True, if string is not null.
       -a file
              Same as -e below.  This is obsolete.
       -b file
              True, if file exists and is a block special file.
       -c file
              True, if file exists and is a character special file.
       -d file
              True, if file exists and is a directory.
       -e file
              True, if file exists.
       -f file
              True, if file exists and is an ordinary file.
       -g file
              True, if file exists and it has its setgid bit set.
       -k file
              True, if file exists and it has its sticky bit set.
       -n string
              True, if length of string is non-zero.
       -o ?option
              True, if option named option is a valid option name.
       -o option
              True, if option named option is on.
       -p file
              True, if file exists and is a fifo special file or a pipe.
       -r file
              True, if file exists and is readable by current process.
       -s file
              True, if file exists and has size greater than zero.
       -t fildes
              True,  if  file  descriptor  number  fildes  is open and associated with a terminal
              device.
       -u file
              True, if file exists and it has its setuid bit set.
       -v name
              True, if variable name is a valid variable name and is set.
       -w file
              True, if file exists and is writable by current process.
       -x file
              True, if file exists and is executable by current process.  If file exists and is a
              directory,  then  true  if  the  current  process  has  permission to search in the
              directory.
       -z string
              True, if length of string is zero.
       -L file
              True, if file exists and is a symbolic link.
       -h file
              True, if file exists and is a symbolic link.
       -N file
              True, if file exists and the modification time is  greater  than  the  last  access
              time.
       -O file
              True, if file exists and is owned by the effective user id of this process.
       -G file
              True, if file exists and its group matches the effective group id of this process.
       -R name
              True if variable name is a name reference.
       -S file
              True, if file exists and is a socket.
       file1 -nt file2
              True, if file1 exists and file2 does not, or file1 is newer than file2.
       file1 -ot file2
              True, if file2 exists and file1 does not, or file1 is older than file2.
       file1 -ef file2
              True, if file1 and file2 exist and refer to the same file.
       string == pattern
              True,  if string matches pattern.  Any part of pattern can be quoted to cause it to
              be matched as a string.  With a successful match to a pattern, the .sh.match  array
              variable will contain the match and sub-pattern matches.
       string = pattern
              Same as == above, but is obsolete.
       string != pattern
              True,  if  string  does not match pattern.  When the string matches the pattern the
              .sh.match array variable will contain the match and sub-pattern matches.
       string =∼ ere
              True if string matches the  pattern  ∼(E)ere  where  ere  is  an  extended  regular
              expression.
       string1 < string2
              True, if string1 comes before string2 based on ASCII value of their characters.
       string1 > string2
              True, if string1 comes after string2 based on ASCII value of their characters.
       The following obsolete arithmetic comparisons are also permitted:
       exp1 -eq exp2
              True, if exp1 is equal to exp2.
       exp1 -ne exp2
              True, if exp1 is not equal to exp2.
       exp1 -lt exp2
              True, if exp1 is less than exp2.
       exp1 -gt exp2
              True, if exp1 is greater than exp2.
       exp1 -le exp2
              True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
              True, if exp1 is greater than or equal to exp2.

       In each of the above expressions, if file is of the form /dev/fd/n, where n is an integer,
       then the test is applied to the open file whose descriptor number is n.

       A compound expression can be constructed  from  these  primitives  by  using  any  of  the
       following, listed in decreasing order of precedence.
       (expression)
              True, if expression is true.  Used to group expressions.
       ! expression
              True if expression is false.
       expression1 && expression2
              True, if expression1 and expression2 are both true.
       expression1 ⎪⎪ expression2
              True, if either expression1 or expression2 is true.

   Input/Output.
       Before  a  command  is  executed,  its  input and output may be redirected using a special
       notation interpreted by the shell.  The following may appear anywhere in a  simple-command
       or  may precede or follow a command and are not passed on to the invoked command.  Command
       substitution, parameter expansion, and arithmetic substitution occur before word or  digit
       is  used  except  as  noted  below.   File  name  generation  occurs  only if the shell is
       interactive and the pattern matches a single file.  Field splitting is not performed.

       In each of the following  redirections,  if  file  is  of  the  form  /dev/sctp/host/port,
       /dev/tcp/host/port,  or  /dev/udp/host/port, where host is a hostname or host address, and
       port is a service given by name or an integer port number, then the  redirection  attempts
       to make a tcp, sctp or udp connection to the corresponding socket.

       No intervening space is allowed between the characters of redirection operators.

       <word         Use file word as standard input (file descriptor 0).

       >word         Use  file word as standard output (file descriptor 1).  If the file does not
                     exist then it is created.  If the file exists, and the noclobber  option  is
                     on, this causes an error; otherwise, it is truncated to zero length.

       >|word        Same as >, except that it overrides the noclobber option.

       >;word        Write  output  to  a  temporary file.  If the command completes successfully
                     rename it to word, otherwise, delete the temporary file.  >;word  cannot  be
                     used with the exec(2).  built-in.

       >>word        Use  file  word  as  standard  output.   If  the file exists, then output is
                     appended to it (by first seeking to the end-of-file); otherwise, the file is
                     created.

       <>word        Open file word for reading and writing as standard output.

       <>;word       The  same  as <>word except that if the command completes successfully, word
                     is truncated to the offset at command completion.  <>;word  cannot  be  used
                     with the exec(2).  built-in.

       <<[-]word     The  shell  input  is  read  up to a line that is the same as word after any
                     quoting has been removed, or to an end-of-file.  No parameter  substitution,
                     command  substitution,  arithmetic  substitution  or file name generation is
                     performed on word.  The resulting document, called a here-document,  becomes
                     the   standard  input.   If  any  character  of  word  is  quoted,  then  no
                     interpretation is placed upon the characters  of  the  document;  otherwise,
                     parameter  expansion,  command  substitution,  and  arithmetic  substitution
                     occur, \new-line is ignored, and \ must be used to quote the  characters  \,
                     $,  `.  If - is appended to <<, then all leading tabs are stripped from word
                     and from the document.  If # is appended to <<, then leading spaces and tabs
                     will  be stripped off the first line of the document and up to an equivalent
                     indentation will be stripped from the remaining lines and from word.  A  tab
                     stop  is assumed to occur at every 8 columns for the purposes of determining
                     the indentation.

       <<<word       A short form of here document in which word  becomes  the  contents  of  the
                     here-document  after  any  parameter  expansion,  command  substitution, and
                     arithmetic substitution occur.

       <&digit       The standard input is duplicated from file descriptor  digit  (see  dup(2)).
                     Similarly for the standard output using >&digit.

       <&digit-      The  file  descriptor  given by digit is moved to standard input.  Similarly
                     for the standard output using >&digit-.

       <&-           The standard input is closed.  Similarly for the standard output using >&-.

       <&p           The input from the co-process is moved to standard input.

       >&p           The output to the co-process is moved to standard output.

       <#((expr))    Evaluate arithmetic expression expr and position file descriptor  0  to  the
                     resulting value bytes from the start of the file.  The variables CUR and EOF
                     evaluate to the current offset  and  end-of-file  offset  respectively  when
                     evaluating expr.

       >#((offset))  The same as <# except applies to file descriptor 1.

       <#pattern     Seeks forward to the beginning of the next line containing pattern.

       <##pattern    The same as <# except that the portion of the file that is skipped is copied
                     to standard output.

       If one of the above is preceded by a digit, with  no  intervening  space,  then  the  file
       descriptor  number referred to is that specified by the digit (instead of the default 0 or
       1).  If one of the above, other than >&- and the ># and <# forms, is preceded by {varname}
       with  no  intervening  space,  then  a file descriptor number > 10 will be selected by the
       shell and stored in the variable varname.  If >&- or the any of the >#  and  <#  forms  is
       preceded  by  {varname}  the  value  of  varname  defines  the file descriptor to close or
       position.  For example:

              ... 2>&1

       means file descriptor 2 is to be opened for writing as a duplicate of  file  descriptor  1
       and

              exec {n}<file

       means open file named file for reading and store the file descriptor number in variable n.

       The  order  in  which redirections are specified is significant.  The shell evaluates each
       redirection in terms of the (file descriptor, file) association at the time of evaluation.
       For example:

              ... 1>fname 2>&1

       first  associates file descriptor 1 with file fname.  It then associates file descriptor 2
       with the file  associated  with  file  descriptor  1  (i.e.   fname).   If  the  order  of
       redirections  were  reversed,  file  descriptor  2  would  be associated with the terminal
       (assuming file descriptor 1 had been) and then file descriptor 1 would be associated  with
       file fname.

       If  a  command  is  followed by & and job control is not active, then the default standard
       input for the command is the empty file /dev/null.  Otherwise,  the  environment  for  the
       execution  of a command contains the file descriptors of the invoking shell as modified by
       input/output specifications.

   Environment.
       The environment (see environ(7)) is a list of  name-value  pairs  that  is  passed  to  an
       executed program in the same way as a normal argument list.  The names must be identifiers
       and the values are character strings.  The shell interacts with the environment in several
       ways.  On invocation, the shell scans the environment and creates a variable for each name
       found, giving it the corresponding value and attributes and marking it  export.   Executed
       commands  inherit  the environment.  If the user modifies the values of these variables or
       creates new ones, using the export or  typeset  -x  commands,  they  become  part  of  the
       environment.   The  environment seen by any executed command is thus composed of any name-
       value pairs originally inherited by the shell, whose values may be modified by the current
       shell, plus any additions which must be noted in export or typeset -x commands.

       The  environment  for any simple-command or function may be augmented by prefixing it with
       one or more variable assignments.  A variable assignment argument is a word  of  the  form
       identifier=value.  Thus:

              TERM=450 cmd args                  and
              (export TERM; TERM=450; cmd args)

       are  equivalent  (as  far  as  the  above execution of cmd is concerned except for special
       built-in commands listed below - those that are preceded with a dagger).

       If the obsolete -k option is set, all variable assignment  arguments  are  placed  in  the
       environment,  even if they occur after the command name.  The following first prints a=b c
       and then c:

              echo a=b c
              set -k
              echo a=b c
       This feature is intended for use with scripts written for early versions of the shell  and
       its use in new scripts is strongly discouraged.  It is likely to disappear someday.

   Functions.
       For  historical reasons, there are two ways to define functions, the name() syntax and the
       function name syntax, described in the Commands section above.  Shell functions  are  read
       in  and stored internally.  Alias names are resolved when the function is read.  Functions
       are executed like commands with the  arguments  passed  as  positional  parameters.   (See
       Execution below.)

       Functions  defined  by  the  function  name  syntax and called by name execute in the same
       process as the caller and share all files and present working directory with  the  caller.
       Traps  caught by the caller are reset to their default action inside the function.  A trap
       condition that is not caught or ignored by the function causes the function  to  terminate
       and  the condition to be passed on to the caller.  A trap on EXIT set inside a function is
       executed in the environment of the  caller  after  the  function  completes.   Ordinarily,
       variables  are  shared between the calling program and the function.  However, the typeset
       special built-in command used within  a  function  defines  local  variables  whose  scope
       includes  the  current  function.   They  can be passed to functions that they call in the
       variable assignment list that precedes the call or as arguments passed as name references.
       Errors within functions return control to the caller.

       Functions  defined  with  the  name()  syntax and functions defined with the function name
       syntax that are invoked with  the  .   special  built-in  are  executed  in  the  caller's
       environment  and  share  all  variables  and  traps  with the caller.  Errors within these
       function executions cause the script that contains them to abort.

       The special built-in command return is used to return from function calls.

       Function names can be listed with the -f or +f option  of  the  typeset  special  built-in
       command.   The  text of functions, when available, will also be listed with -f.  Functions
       can be undefined with the -f option of the unset special built-in command.

       Ordinarily, functions are unset when the shell executes a shell  script.   Functions  that
       need  to  be  defined  across  separate  invocations  of  the  shell should be placed in a
       directory and the FPATH variable should contain the name of this directory.  They may also
       be specified in the ENV file.

   Discipline Functions.
       Each  variable  can  have zero or more discipline functions associated with it.  The shell
       initially understands the discipline names get, set, append, and unset but  can  be  added
       when  defining  new  types.   On  most  systems  others can be added at run time via the C
       programming interface extension provided by the builtin  built-in  utility.   If  the  get
       discipline  is  defined  for  a  variable,  it  is  invoked whenever the given variable is
       referenced.  If the variable .sh.value is assigned a value inside the discipline function,
       the  referenced  variable  will  evaluate to this value instead.  If the set discipline is
       defined for a variable, it is invoked whenever the given variable is assigned a value.  If
       the  append  discipline  is  defined  for  a  variable,  it is invoked whenever a value is
       appended to the given variable.  The variable .sh.value is given the value of the variable
       before  invoking  the discipline, and the variable will be assigned the value of .sh.value
       after the discipline completes.  If .sh.value is unset inside the  discipline,  then  that
       value  is  unchanged.   If  the  unset discipline is defined for a variable, it is invoked
       whenever the given variable is unset.  The variable will not be unset unless it  is  unset
       explicitly from within this discipline function.

       The  variable .sh.name contains the name of the variable for which the discipline function
       is called, .sh.subscript is the subscript of the variable, and .sh.value will contain  the
       value being assigned inside the set discipline function.  The variable _ is a reference to
       the variable including the subscript if any.  For the set discipline,  changing  .sh.value
       will  change  the value that gets assigned.  Finally, the expansion ${var.name}, when name
       is the name of a discipline, and there is no variable of this name, is equivalent  to  the
       command substitution ${ var.name;}.

   Name Spaces.
       Commands  and  functions that are executed as part of the list of a namespace command that
       modify variables or create new ones, create a new variable whose name is the name  of  the
       name  space  as  given by identifier preceded by ..  When a variable whose name is name is
       referenced, it is first  searched  for  using  .identifier.name.   Similarly,  a  function
       defined  by a command in the namespace list is created using the name space name  preceded
       by a ..

       When  the list of a namespace command contains a namespace command, the names of variables
       and  functions  that  are created consist of the variable or function name preceded by the
       list of identifiers each preceded by ..

       Outside of a name space, a variable or  function  created  inside  a  name  space  can  be
       referenced by preceding it with the name space name.

       By default, variables staring with .sh are in the sh name space.

   Type Variables.
       Typed variables provide a way to create data structure and objects.  A type can be defined
       either by a shared library, by the enum built-in command described below, or by using  the
       new  -T  option  of the typeset built-in command.  With the -T option of typeset, the type
       name, specified as an option argument to -T, is set with a  compound  variable  assignment
       that  defines  the  type.   Function  definitions  can appear inside the compound variable
       assignment and these become discipline functions for this  type  and  can  be  invoked  or
       redefined  by  each  instance of the type.  The function name create is treated specially.
       It is invoked for each instance of the type that is  created  but  is  not  inherited  and
       cannot be redefined for each instance.

       When  a type is defined a special built-in command of that name is added.  These built-ins
       are declaration commands and follow the same expansion rules as all the  special  built-in
       commands  defined  below that are preceded by ††.  These commands can subsequently be used
       inside further type definitions.  The man page for these  commands  can  be  generated  by
       using the --man option or any of the other -- options described with getopts.  The -r, -a,
       -A, -h, and -S options of typeset are permitted with each of these new built-ins.

       An instance of a type is created by invoking  the  type  name  followed  by  one  or  more
       instance names.  Each instance of the type is initialized with a copy of the sub-variables
       except for sub-variables that are defined with the -S option.  Variables defined with  the
       -S  are  shared  by  all instances of the type.  Each instance can change the value of any
       sub-variable and can also define new discipline functions  of  the  same  names  as  those
       defined  by  the  type definition as well as any standard discipline names.  No additional
       sub-variables can be defined for any instance.

       When defining a type, if the value of a sub-variable is not set and the  -r  attribute  is
       specified, it causes the sub-variable to be a required sub-variable.  Whenever an instance
       of a type is created, all required sub-variables must be specified.   These  sub-variables
       become readonly in each instance.

       When  unset  is invoked on a sub-variable within a type, and the -r attribute has not been
       specified for this field, the value is reset to the default  value  associative  with  the
       type.   Invoking  unset  on  a type instance not contained within another type deletes all
       sub-variables and the variable itself.

       A type definition can be derived from another type definition by defining the  first  sub-
       variable name as _ and defining its type as the base type.  Any remaining definitions will
       be additions and modifications that apply to the new type.  If the new type  name  is  the
       same  is  that  of  the base type, the type will be replaced and the original type will no
       longer be accessible.

       The typeset command with the -T and no option argument or operands will write all the type
       definitions  to  standard  output  in  a  form that that can be read in to create all they
       types.

   Jobs.
       If the monitor option of the set command is turned on, an interactive shell  associates  a
       job  with  each  pipeline.  It keeps a table of current jobs, printed by the jobs command,
       and assigns them small integer numbers.  When a job is started asynchronously with &,  the
       shell prints a line which looks like:

            [1] 1234

       indicating  that  the  job  which  was started asynchronously was job number 1 and had one
       (top-level) process, whose process id was 1234.

       This paragraph and the next require features that are not in all versions of UNIX and  may
       not  apply.  If you are running a job and wish to do something else you may hit the key ^Z
       (control-Z) which sends a STOP signal to the current job.  The shell  will  then  normally
       indicate  that  the  job  has  been  `Stopped',  and  print  another prompt.  You can then
       manipulate the state of this job, putting it in the background with the bg command, or run
       some  other  commands  and then eventually bring the job back into the foreground with the
       foreground command fg.  A ^Z takes effect immediately and is like  an  interrupt  in  that
       pending output and unread input are discarded when it is typed.

       A  job  being  run  in  the  background  will  stop if it tries to read from the terminal.
       Background jobs are normally allowed to produce output, but this can be disabled by giving
       the  command stty tostop.  If you set this tty option, then background jobs will stop when
       they try to produce output like they do when they try to read input.

       A job pool is a collection of jobs started with list & associated with a name.

       There are several ways to refer to jobs in the shell.  A job can be  referred  to  by  the
       process id of any process of the job or by one of the following:
       %number
              The job with the given number.
       pool   All the jobs in the job pool named by pool.
       pool.number
              The job number number in the job pool named by pool.
       %string
              Any job whose command line begins with string.
       %?string
              Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous  job.   In  addition,  unless  noted  otherwise,  wherever  a  job  can be
              specified, the name of a background job pool can be used to represent all the  jobs
              in that pool.

       The  shell  learns  immediately whenever a process changes state.  It normally informs you
       whenever a job becomes blocked so that no further progress  is  possible,  but  only  just
       before  it prints a prompt.  This is done so that it does not otherwise disturb your work.
       The notify option of the set command causes the shell to print these job  change  messages
       as soon as they occur.

       When  the  monitor  option is on, each background job that completes triggers any trap set
       for CHLD.

       When you try to leave the shell while jobs are running or stopped, you will be warned that
       `You  have stopped(running) jobs.'  You may use the jobs command to see what they are.  If
       you immediately try to exit again, the shell will not warn you  a  second  time,  and  the
       stopped jobs will be terminated.  When a login shell receives a HUP signal, it sends a HUP
       signal to each job that has not been disowned with the disown built-in  command  described
       below.

   Signals.
       The  INT and QUIT signals for an invoked command are ignored if the command is followed by
       & and the monitor option is not active.  Otherwise, signals have the values  inherited  by
       the shell from its parent (but see also the trap built-in command below).

   Execution.
       Each time a command is read, the above substitutions are carried out.  If the command name
       matches one of the Special Built-in Commands listed  below,  it  is  executed  within  the
       current  shell  process.   Next,  the  command name is checked to see if it matches a user
       defined function.  If it does, the positional parameters are saved and then reset  to  the
       arguments of the function call.  A function is also executed in the current shell process.
       When the function completes or issues a return, the positional parameter list is restored.
       For  functions  defined  with  the  function  name syntax, any trap set on EXIT within the
       function is executed.  The exit value of a function is  the  value  of  the  last  command
       executed.  If a command name is not a special built-in command or a user defined function,
       but it is one of the built-in commands listed below, it is executed in the  current  shell
       process.

       The shell variables PATH followed by the variable FPATH defines the list of directories to
       search for the command name.  Alternative directory names are separated by  a  colon  (:).
       The  default  path is /bin:/usr/bin: (specifying /bin, /usr/bin, and the current directory
       in that order).  The current directory can be specified by two or more adjacent colons, or
       by  a  colon  at the beginning or end of the path list.  If the command name contains a /,
       then the search path is not used.  Otherwise, each directory in the  list  of  directories
       defined  by  PATH  and  FPATH  is  checked  in  order.  If the directory being searched is
       contained in FPATH and contains a file whose name matches the command being searched, then
       this file is loaded into the current shell environment as if it were the argument to the .
       command except that only preset aliases are expanded, and a function of the given name  is
       executed as described above.

       If  this  directory is not in FPATH the shell first determines whether there is a built-in
       version of a command corresponding to a given pathname and if so  it  is  invoked  in  the
       current  process.   If  no  built-in is found, the shell checks for a file named .paths in
       this directory.  If found and there is a line of the form FPATH=path where path  names  an
       existing  directory  then  that  directory is searched after immediately after the current
       directory as if it were found in the FPATH variable.  If path does not begin with /, it is
       checked for relative to the directory being searched.

       The  .paths  file is then checked  for a line of the form PLUGIN_LIB=libname [ : libname ]
       ... .  Each library named by libname will be searched for as if it were an option argument
       to  builtin  -f, and if it contains a built-in of the specified name this will be executed
       instead of a command by this name.  Any built-in loaded from a library found this way will
       be associated with the directory containing the .paths file so it will only execute if not
       found in an earlier directory.

       Finally, the directory will be checked for a file of the given  name.   If  the  file  has
       execute  permission  but is not an a.out file, it is assumed to be a file containing shell
       commands.  A separate shell is spawned to read it.  All non-exported variables are removed
       in  this  case.   If the shell command file doesn't have read permission, or if the setuid
       and/or setgid bits are set on the file, then the shell executes an agent whose job  it  is
       to set up the permissions and execute the shell with the shell command file passed down as
       an open file.  If the .paths contains a line of the form name=value in the first or second
       line, then the environment variable name is modified by prepending the directory specified
       by value to the directory list.  If value is not an absolute directory, then it  specifies
       a  directory  relative to the directory that the executable was found.  If the environment
       variable name does not already exist it will be added to  the  environment  list  for  the
       specified  command.   A  parenthesized command is executed in a sub-shell without removing
       non-exported variables.

   Command Re-entry.
       The text of the last HISTSIZE (default 512) commands entered from  a  terminal  device  is
       saved  in  a history file.  The file $HOME/.sh_history is used if the HISTFILE variable is
       not set or if the file it names is not writable.  A shell can access the commands  of  all
       interactive  shells  which use the same named HISTFILE.  The built-in command hist is used
       to list or edit a portion of this file.  The portion of the file to be  edited  or  listed
       can  be  selected by number or by giving the first character or characters of the command.
       A single command or range of commands can be specified.  If you do not specify  an  editor
       program  as  an  argument  to  hist  then  the value of the variable HISTEDIT is used.  If
       HISTEDIT is unset, the obsolete variable FCEDIT is used.  If FCEDIT is not  defined,  then
       /usr/bin/ex  is  used.   The edited command(s) is printed and re-executed upon leaving the
       editor unless you quit without writing.  The -s option  (and  in  obsolete  versions,  the
       editor  name  -) is used to skip the editing phase and to re-execute the command.  In this
       case a substitution parameter of the form old=new can be used to modify the command before
       execution.  For example, with the preset alias r, which is aliased to ′hist -s′, typing `r
       bad=good c' will re-execute the most recent  command  which  starts  with  the  letter  c,
       replacing the first occurrence of the string bad with the string good.

   In-line Editing Options.
       Normally,  each  command line entered from a terminal device is simply typed followed by a
       new-line (`RETURN' or `LINE FEED').  If either the emacs, gmacs, or vi option  is  active,
       the  user  can  edit  the  command  line.   To  be  in  either of these edit modes set the
       corresponding option.  An editing option is automatically selected each time the VISUAL or
       EDITOR variable is assigned a value ending in either of these option names.

       The  editing  features require that the user's terminal accept `RETURN' as carriage return
       without line feed and that a space (` ') must  overwrite  the  current  character  on  the
       screen.

       Unless the multiline option is on, the editing modes implement a concept where the user is
       looking through a window at the current line.  The window width is the value of COLUMNS if
       it  is  defined, otherwise 80.  If the window width is too small to display the prompt and
       leave at least 8 columns to enter input, the prompt is truncated from the  left.   If  the
       line  is  longer  than  the  window width minus two, a mark is displayed at the end of the
       window to notify the user.  As the cursor moves and  reaches  the  window  boundaries  the
       window  will  be centered about the cursor.  The mark is a > (<, *) if the line extends on
       the right (left, both) side(s) of the window.

       The search commands in each edit mode provide access to the history  file.   Only  strings
       are matched, not patterns, although a leading ^ in the string restricts the match to begin
       at the first character in the line.

       Each of the edit modes has an operation to  list  the  files  or  commands  that  match  a
       partially  entered  word.   When  applied to the first word on the line, or the first word
       after a ;, , &, or (, and the word does not begin with  or contain  a  /,  the  list  of
       aliases,  functions, and executable commands defined by the PATH variable that could match
       the partial word is displayed.  Otherwise, the list of files that match the given word  is
       displayed.   If the partially entered word does not contain any file expansion characters,
       a * is appended before generating these lists.  After displaying the generated  list,  the
       input  line  is  redrawn.   These operations are called command name listing and file name
       listing, respectively.  There are additional  operations,  referred  to  as  command  name
       completion and file name completion, which compute the list of matching commands or files,
       but instead of printing the list, replace the current word  with  a  complete  or  partial
       match.  For file name completion, if the match is unique, a / is appended if the file is a
       directory and a space is appended if the file is not a directory.  Otherwise, the  longest
       common  prefix for all the matching files replaces the word.  For command name completion,
       only the portion of the file names after the last / are used to find the  longest  command
       prefix.   If  only  a  single name matches this prefix, then the word is replaced with the
       command name followed by a space.  When using a tab for completion that does not  yield  a
       unique  match,  a subsequent tab will provide a numbered list of matching alternatives.  A
       specific selection can be made by entering the selection number followed by a tab.

   Key Bindings.
       The KEYBD trap can be used to intercept keys as they are typed and change  the  characters
       that  are  actually  seen  by  the  shell.  This trap is executed after each character (or
       sequence of characters when the first character is ESC) is entered while  reading  from  a
       terminal.   The  variable  .sh.edchar  contains  the character or character sequence which
       generated the trap.  Changing the value of .sh.edchar in the trap action causes the  shell
       to  behave  as  if  the  new value were entered from the keyboard rather than the original
       value.

       The variable .sh.edcol is set to the input column number of the cursor at the time of  the
       input.   The  variable  .sh.edmode is set to ESC when in vi insert mode (see below) and is
       null otherwise.  By prepending ${.sh.editmode} to a value assigned to .sh.edchar  it  will
       cause the shell to change to control mode if it is not already in this mode.

       This  trap  is  not  invoked for characters entered as arguments to editing directives, or
       while reading input for a character search.

   Emacs Editing Mode.
       This mode is entered by enabling either the emacs or gmacs option.   The  only  difference
       between  these two modes is the way they handle ^T.  To edit, the user moves the cursor to
       the point needing correction and then inserts or deletes characters or  words  as  needed.
       All  the  editing  commands  are control characters or escape sequences.  The notation for
       control characters is caret (^) followed  by  the  character.   For  example,  ^F  is  the
       notation  for  control F.  This is entered by depressing `f' while holding down the `CTRL'
       (control) key.  The `SHIFT' key is not depressed.  (The notation  ^?   indicates  the  DEL
       (delete) key.)

       The  notation  for  escape  sequences  is  M-  followed  by a character.  For example, M-f
       (pronounced Meta f) is entered by depressing ESC (ascii 033) followed by `f'.  (M-F  would
       be the notation for ESC followed by `SHIFT' (capital) `F'.)

       All edit commands operate from any place on the line (not just at the beginning).  Neither
       the `RETURN' nor the `LINE FEED' key is entered after edit commands except when noted.

       ^F        Move cursor forward (right) one character.
       M-[C      Move cursor forward (right) one character.
       M-f       Move cursor forward one word.  (The emacs editor's idea of a word is a string of
                 characters consisting of only letters, digits and underscores.)
       ^B        Move cursor backward (left) one character.
       M-[D      Move cursor backward (left) one character.
       M-b       Move cursor backward one word.
       ^A        Move cursor to start of line.
       M-[H      Move cursor to start of line.
       ^E        Move cursor to end of line.
       M-[Y      Move cursor to end of line.
       ^]char    Move cursor forward to character char on current line.
       M-^]char  Move cursor backward to character char on current line.
       ^X^X      Interchange the cursor and mark.
       erase     (User  defined  erase character as defined by the stty(1) command, usually ^H or
                 #.)  Delete previous character.
       lnext     (User defined literal next character as defined by the stty(1) command, or ^V if
                 not defined.)  Removes the next character's editing features (if any).
       ^D        Delete current character.
       M-d       Delete current word.
       M-^H      (Meta-backspace) Delete previous word.
       M-h       Delete previous word.
       M-^?      (Meta-DEL)  Delete  previous  word (if your interrupt character is ^?  (DEL, the
                 default) then this command will not work).
       ^T        Transpose current character with previous character and advance  the  cursor  in
                 emacs mode.  Transpose two previous characters in gmacs mode.
       ^C        Capitalize current character.
       M-c       Capitalize current word.
       M-l       Change the current word to lower case.
       ^K        Delete  from  the  cursor  to  the  end of the line.  If preceded by a numerical
                 parameter whose value is less than the current cursor position, then delete from
                 given  position  up  to  the cursor.  If preceded by a numerical parameter whose
                 value is greater than the current cursor position, then delete from cursor up to
                 given cursor position.
       ^W        Kill from the cursor to the mark.
       M-p       Push the region from the cursor to the mark on the stack.
       kill      (User  defined  kill character as defined by the stty command, usually ^G or @.)
                 Kill the entire current line.  If two kill characters are entered in succession,
                 all  kill  characters  from  then  on cause a line feed (useful when using paper
                 terminals).
       ^Y        Restore last item removed from line. (Yank item back to the line.)
       ^L        Line feed and print current line.
       M-^L      Clear the screen.
       ^@        (Null character) Set mark.
       M-space   (Meta space) Set mark.
       ^J        (New line) Execute the current line.
       ^M        (Return) Execute the current line.
       eof       End-of-file character, normally ^D, is processed as an End-of-file only  if  the
                 current line is null.
       ^P        Fetch  previous  command.   Each time ^P is entered the previous command back in
                 time is accessed.  Moves back one line when not on the first line  of  a  multi-
                 line command.
       M-[A      If  the cursor is at the end of the line, it is equivalent to ^R with string set
                 to the contents of the current line.  Otherwise, it is equivalent to ^P.
       M-<       Fetch the least recent (oldest) history line.
       M->       Fetch the most recent (youngest) history line.
       ^N        Fetch next command line.  Each time ^N is entered the next command line  forward
                 in time is accessed.
       M-[B      Equivalent to ^N.
       ^Rstring  Reverse  search  history  for  a  previous command line containing string.  If a
                 parameter of zero is given, the search is forward.  String is  terminated  by  a
                 `RETURN'  or  `NEW LINE'.   If  string is preceded by a ^, the matched line must
                 begin with string.  If string is omitted, then the next command line  containing
                 the  most  recent string is accessed.  In this case a parameter of zero reverses
                 the direction of the search.
       ^O        Operate - Execute the current line and fetch the next line relative  to  current
                 line from the history file.
       M-digits  (Escape)  Define  numeric  parameter, the digits are taken as a parameter to the
                 next command.  The commands that accept a parameter are ^F, ^B, erase,  ^C,  ^D,
                 ^K, ^R, ^P, ^N, ^], M-., M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
       M-letter  Soft-key  -  Your alias list is searched for an alias by the name _letter and if
                 an alias of this name is defined, its value will be inserted on the input queue.
                 The letter must not be one of the above meta-functions.
       M-[letter Soft-key  - Your alias list is searched for an alias by the name __letter and if
                 an alias of this name is defined, its value will be inserted on the input queue.
                 This can be used to program function keys on many terminals.
       M-.       The last word of the previous command is inserted on the line.  If preceded by a
                 numeric parameter, the value of this parameter determines which word  to  insert
                 rather than the last word.
       M-_       Same as M-..
       M-*       Attempt  file  name  generation on the current word.  An asterisk is appended if
                 the word doesn't match any file or contain any special pattern characters.
       M-ESC     Command or file name completion as described above.
       ^I tab    Attempts command or file name completion  as  described  above.   If  a  partial
                 completion  occurs,  repeating  this  will behave as if M-= were entered.  If no
                 match is found or entered after space, a tab is inserted.
       M-=       If not preceded by a numeric  parameter,  it  generates  the  list  of  matching
                 commands or file names as described above.  Otherwise, the word under the cursor
                 is replaced by the item corresponding to the value of the numeric parameter from
                 the  most  recently  generated  command or file list.  If the cursor is not on a
                 word, it is inserted instead.
       ^U        Multiply parameter of next command by 4.
       \         Escape next character.  Editing characters, the user's erase, kill and interrupt
                 (normally ^?)  characters may be entered in a command line or in a search string
                 if preceded by a \.  The \ removes the next  character's  editing  features  (if
                 any).
       M-^V      Display version of the shell.
       M-#       If  the  line  does  not begin with a #, a # is inserted at the beginning of the
                 line and after each new-line, and the line is entered.  This causes a comment to
                 be  inserted in the history file.  If the line begins with a #, the # is deleted
                 and one # after each new-line is also deleted.

   Vi Editing Mode.
       There are two typing modes.  Initially, when you enter a command  you  are  in  the  input
       mode.   To  edit, the user enters control mode by typing ESC (033) and moves the cursor to
       the point needing correction and then inserts or deletes characters or  words  as  needed.
       Most control commands accept an optional repeat count prior to the command.

       When in vi mode on most systems, canonical processing is initially enabled and the command
       will be echoed again if the speed is 1200 baud or greater  and  it  contains  any  control
       characters  or  less  than  one  second has elapsed since the prompt was printed.  The ESC
       character terminates canonical processing for the remainder of the command  and  the  user
       can  then modify the command line.  This scheme has the advantages of canonical processing
       with the type-ahead echoing of raw mode.

       If the option viraw is also set,  the  terminal  will  always  have  canonical  processing
       disabled.  This mode is implicit for systems that do not support two alternate end of line
       delimiters, and may be helpful for certain terminals.

        Input Edit Commands
              By default the editor is in input mode.
              erase     (User defined erase character as defined by the stty command, usually  ^H
                        or #.)  Delete previous character.
              ^W        Delete  the  previous  blank  separated  word.  On some systems the viraw
                        option may be required for this to work.
              eof       As the first character of the line causes the shell to  terminate  unless
                        the ignoreeof option is set.  Otherwise this character is ignored.
              lnext     (User  defined  literal next character as defined by the stty(1) or ^V if
                        not defined.)  Removes the next character's editing  features  (if  any).
                        On some systems the viraw option may be required for this to work.
              \         Escape the next erase or kill character.
              ^I tab    Attempts  command  or file name completion as described above and returns
                        to input mode.  If a  partial  completion  occurs,  repeating  this  will
                        behave  as  if = were entered from control mode.  If no match is found or
                        entered after space, a tab is inserted.
        Motion Edit Commands
              These commands will move the cursor.
              [count]l  Cursor forward (right) one character.
              [count][C Cursor forward (right) one character.
              [count]w  Cursor forward one alpha-numeric word.
              [count]W  Cursor to the beginning of the next word that follows a blank.
              [count]e  Cursor to end of word.
              [count]E  Cursor to end of the current blank delimited word.
              [count]h  Cursor backward (left) one character.
              [count][D Cursor backward (left) one character.
              [count]b  Cursor backward one word.
              [count]B  Cursor to preceding blank separated word.
              [count]  Cursor to column count.
              [count]fc Find the next character c in the current line.
              [count]Fc Find the previous character c in the current line.
              [count]tc Equivalent to f followed by h.
              [count]Tc Equivalent to F followed by l.
              [count];  Repeats count times, the last single character find command, f, F, t,  or
                        T.
              [count],  Reverses the last single character find command count times.
              0         Cursor to start of line.
              ^         Cursor to start of line.
              [H        Cursor to first non-blank character in line.
              $         Cursor to end of line.
              [Y        Cursor to end of line.
              %         Moves  to  balancing (, ), {, }, [, or ].  If cursor is not on one of the
                        above characters, the remainder of the line is  searched  for  the  first
                        occurrence of one of the above characters first.
        Search Edit Commands
              These commands access your command history.
              [count]k  Fetch previous command.  Each time k is entered the previous command back
                        in time is accessed.
              [count]-  Equivalent to k.
              [count][A If cursor is at the end of the line it is equivalent to / with string^set
                        to the contents of the current line.  Otherwise, it is equivalent to k.
              [count]j  Fetch  next  command.  Each time j is entered the next command forward in
                        time is accessed.
              [count]+  Equivalent to j.
              [count][B Equivalent to j.
              [count]G  The command number count is fetched.  The default  is  the  least  recent
                        history command.
              /string   Search backward through history for a previous command containing string.
                        String is terminated by a `RETURN' or `NEW LINE'.  If string is  preceded
                        by  a ^, the matched line must begin with string.  If string is null, the
                        previous string will be used.
              ?string   Same as / except that search will be in the forward direction.
              n         Search for next match of the last pattern to / or ?  commands.
              N         Search for next match of the last pattern to  /  or  ?,  but  in  reverse
                        direction.
        Text Modification Edit Commands
              These commands will modify the line.
              a         Enter input mode and enter text after the current character.
              A         Append text to the end of the line.  Equivalent to $a.
              [count]cmotion
              c[count]motion
                        Delete current character through the character that motion would move the
                        cursor to and enter input mode.  If motion is c, the entire line will  be
                        deleted and input mode entered.
              C         Delete  the  current  character  through  the end of line and enter input
                        mode.  Equivalent to c$.
              S         Equivalent to cc.
              [count]s  Replace characters under the cursor in input mode.
              D         Delete the current character through the end of line.  Equivalent to d$.
              [count]dmotion
              d[count]motion
                        Delete current character through the character that motion would move to.
                        If motion is d , the entire line will be deleted.
              i         Enter input mode and insert text before the current character.
              I         Insert text before the beginning of the line.  Equivalent to 0i.
              [count]P  Place the previous text modification before the cursor.
              [count]p  Place the previous text modification after the cursor.
              R         Enter input mode and replace characters on the screen with characters you
                        type overlay fashion.
              [count]rc Replace the count character(s) starting at the  current  cursor  position
                        with c, and advance the cursor.
              [count]x  Delete current character.
              [count]X  Delete preceding character.
              [count].  Repeat the previous text modification command.
              [count]  Invert  the case of the count character(s) starting at the current cursor
                        position and advance the cursor.
              [count]_  Causes the count word of the previous command to be  appended  and  input
                        mode entered.  The last word is used if count is omitted.
              *         Causes  an  * to be appended to the current word and file name generation
                        attempted.  If no match is found, it rings the bell.  Otherwise, the word
                        is replaced by the matching pattern and input mode is entered.
              \         Command or file name completion as described above.
        Other Edit Commands
              Miscellaneous commands.
              [count]ymotion
              y[count]motion
                        Yank  current  character  through  character  that  motion would move the
                        cursor to and puts them into the delete buffer.  The text and cursor  are
                        unchanged.
              yy        Yanks the entire line.
              Y         Yanks from current position to end of line.  Equivalent to y$.
              u         Undo the last text modifying command.
              U         Undo all the text modifying commands performed on the line.
              [count]v  Returns  the  command hist -e ${VISUAL:-${EDITOR:-vi}} count in the input
                        buffer.  If count is omitted, then the current line is used.
              ^L        Line feed and print current line.  Has effect only in control mode.
              ^J        (New line) Execute the current line, regardless of mode.
              ^M        (Return) Execute the current line, regardless of mode.
              #         If the first character of the command is a #, then this  command  deletes
                        this  #  and  each  #  that follows a newline.  Otherwise, sends the line
                        after inserting a # in front of each line in  the  command.   Useful  for
                        causing  the  current line to be inserted in the history as a comment and
                        uncommenting previously commented commands in the history file.
              [count]=  If count is not specified, it generates the list of matching commands  or
                        file  names as described above.  Otherwise, the word under the the cursor
                        is replaced by the count item from the most recently generated command or
                        file list.  If the cursor is not on a word, it is inserted instead.
              @letter   Your  alias  list  is searched for an alias by the name _letter and if an
                        alias of this name is defined, its value will be inserted  on  the  input
                        queue for processing.
              ^V        Display version of the shell.

   Built-in Commands.
       The following simple-commands are executed in the shell process.  Input/Output redirection
       is permitted.  Unless otherwise indicated, the output is written on file descriptor 1  and
       the exit status, when there is no syntax error, is zero.  Except for :, true, false, echo,
       newgrp, and login, all built-in commands accept -- to indicate end of options.  They  also
       interpret the option --man as a request to display the man page onto standard error and -?
       as a help request which prints a usage message  on  standard  error.   Commands  that  are
       preceded  by  one or two † symbols are special built-in commands and are treated specially
       in the following ways:
       1.     Variable assignment lists preceding the command remain in effect when  the  command
              completes.
       2.     I/O redirections are processed after variable assignments.
       3.     Errors cause a script that contains them to abort.
       4.     They are not valid function names.
       5.     Words  following  a  command  preceded  by  †† that are in the format of a variable
              assignment are expanded with the same rules as a variable assignment.   This  means
              that  tilde substitution is performed after the = sign and field splitting and file
              name generation are not performed.  These are called declaration built-ins.

       † : [ arg ... ]
              The command only expands parameters.

       † . name [ arg ... ]
              If name is a function defined with the function  name  reserved  word  syntax,  the
              function is executed in the current environment (as if it had been defined with the
              name() syntax.)  Otherwise if name refers to a  file,  the  file  is  read  in  its
              entirety  and  the  commands  are  executed  in the current shell environment.  The
              search path specified by PATH is used to find the directory  containing  the  file.
              If  any  arguments  arg  are  given,  they  become  the positional parameters while
              processing the .  command and the original positional parameters are restored  upon
              completion.  Otherwise the positional parameters are unchanged.  The exit status is
              the exit status of the last command executed.

       †† alias [ -ptx ]  [ name[ =value  ] ] ...
              alias with no arguments prints the list  of  aliases  in  the  form  name=value  on
              standard  output.   The  -p option causes the word alias to be inserted before each
              one.  When one or more arguments are given, an alias is defined for each name whose
              value  is  given.  A trailing space in value causes the next word to be checked for
              alias substitution.  The obsolete -t  option  is  used  to  set  and  list  tracked
              aliases.   The  value  of a tracked alias is the full pathname corresponding to the
              given name.  The value becomes undefined when the value of PATH is  reset  but  the
              alias  remains  tracked.  Without the -t option, for each name in the argument list
              for which no value is given, the name and value  of  the  alias  is  printed.   The
              obsolete  -x option has no effect.  The exit status is non-zero if a name is given,
              but no value, and no alias has been defined for the name.

       bg [ job... ]
              This command is only on systems that support job control.  Puts each specified  job
              into  the  background.   The  current  job  is  put in the background if job is not
              specified.  See Jobs for a description of the format of job.

       † break [ n ]
              Exit from the enclosing for, while, until,  or  select  loop,  if  any.   If  n  is
              specified, then break n levels.

       builtin [ -ds ] [ -f file ] [ name ... ]
              If  name is not specified, and no -f option is specified, the built-ins are printed
              on standard output.  The -s option prints only the special  built-ins.   Otherwise,
              each  name represents the pathname whose basename is the name of the built-in.  The
              entry point function name is determined by prepending b_ to the built-in  name.   A
              built-in  specified by a pathname will only be executed when that pathname would be
              found during the path search.  Built-ins found in libraries loaded via  the  .paths
              file  will  be  associate  with the pathname of the directory containing the .paths
              file.

       The ISO C/C++ prototype is b_mycommand(int argc, char  *argv[],  void  *context)  for  the
       builtin  command  mycommand  where  argv  is  array  an of argc elements and context is an
       optional pointer to a Shell_t structure as described in <ast/shell.h>.
       Special built-ins cannot be bound to a pathname or deleted.  The -d option deletes each of
       the  given  built-ins.   On  systems  that  support dynamic loading, the -f option names a
       shared library containing the code  for  built-ins.   The  shared  library  prefix  and/or
       suffix, which depend on the system, can be omitted.  Once a library is loaded, its symbols
       become available for  subsequent  invocations  of  builtin.   Multiple  libraries  can  be
       specified with separate invocations of the builtin command.  Libraries are searched in the
       reverse order in which they are specified.  When a library  is  loaded,  it  looks  for  a
       function  in  the  library  whose  name  is  lib_init()  and invokes this function with an
       argument of 0.

       cd [ -LP ] [ arg ]
       cd [ -LP ] old new
              This command can be in either of two forms.  In  the  first  form  it  changes  the
              current  directory  to  arg.   If arg is - the directory is changed to the previous
              directory.  The shell variable HOME is the default arg.  The variable PWD is set to
              the  current  directory.  The shell variable CDPATH defines the search path for the
              directory containing arg.  Alternative directory names are  separated  by  a  colon
              (:).  The default path is <null> (specifying the current directory).  Note that the
              current directory is specified by a null path name, which  can  appear  immediately
              after  the  equal  sign  or  between the colon delimiters anywhere else in the path
              list.  If arg begins with a / then the search path is not  used.   Otherwise,  each
              directory in the path is searched for arg.
              The  second form of cd substitutes the string new for the string old in the current
              directory name, PWD, and tries to change to this new directory.
              By default, symbolic link names are treated literally when  finding  the  directory
              name.  This is equivalent to the -L option.  The -P option causes symbolic links to
              be resolved when determining the directory.  The last instance of -L or -P  on  the
              command line determines which method is used.
              The cd command may not be executed by rksh.  rksh93.

       command [ -pvxV ] name [ arg ... ]
              Without  the  -v  or  -V options, command executes name with the arguments given by
              arg.  The -p option causes a default path  to  be  searched  rather  than  the  one
              defined  by  the  value  of  PATH.  Functions will not be searched for when finding
              name.  In addition, if name refers to a  special  built-in,  none  of  the  special
              properties  associated with the leading daggers will be honored.  (For example, the
              predefined alias redirect=′command exec′ prevents a script from terminating when an
              invalid  redirection  is  given.)   With  the -x option, if command execution would
              result in a failure because there are too many arguments, errno  E2BIG,  the  shell
              will  invoke  command  name  multiple  times with a subset of the arguments on each
              invocation.  Arguments that occur prior to the first word that expands to  multiple
              arguments and after the last word that expands to multiple arguments will be passed
              on each invocation.  The exit status will be the maximum  invocation  exit  status.
              With  the -v option, command is equivalent to the built-in whence command described
              below.  The -V option causes command to act like whence -v.

       † continue [ n ]
              Resume the next iteration of the enclosing for, while, until, or select loop.  If n
              is specified, then resume at the n-th enclosing loop.

       disown [ job... ]
              Causes  the shell not to send a HUP signal to each given job, or all active jobs if
              job is omitted, when a login shell terminates.

       echo [ arg ... ]
              When the first arg does not begin with a -, and none of the arguments contain a  \,
              then  echo  prints  each  of its arguments separated by a space and terminated by a
              new-line.  Otherwise, the behavior of echo is system dependent and print or  printf
              described below should be used.  See echo(1) for usage and description.

       †† enum [ -i  ] type[=(value ...) ]
              Creates a declaration command named type that is an integer type that allows one of
              the specified values as enumeration names.  If =(value ...) is omitted,  then  type
              must  be  an  indexed  array variable with at least two elements and the values are
              taken  from  this  array  variable.   If  -i  is  specified  the  values  are  case
              insensitive.

       † eval [ arg ... ]
              The arguments are read as input to the shell and the resulting command(s) executed.

       † exec [ -c ] [ -a name ] [ arg ... ]
              If  arg  is  given,  the command specified by the arguments is executed in place of
              this shell without creating a new process.  The -c option causes the environment to
              be   cleared   before  applying  variable  assignments  associated  with  the  exec
              invocation.  The -a option causes name rather than the first arg, to become argv[0]
              for  the  new  process.   Input/output  arguments may appear and affect the current
              process.  If arg is not given, the  effect  of  this  command  is  to  modify  file
              descriptors  as prescribed by the input/output redirection list.  In this case, any
              file descriptor numbers greater than 2 that are  opened  with  this  mechanism  are
              closed when invoking another program.

       † exit [ n ]
              Causes  the  shell  to exit with the exit status specified by n.  The value will be
              the least significant 8 bits of the specified status.  If n is  omitted,  then  the
              exit  status  is that of the last command executed.  An end-of-file will also cause
              the shell to exit except for a shell which has the ignoreeof option (see set below)
              turned on.

       †† export [ -p ] [ name[=value] ] ...
              If  name  is  not  given,  the  names  and  values of each variable with the export
              attribute are printed with the values quoted in a manner that allows them to be re-
              input.   The export command is the same as typeset -x except that if you use export
              within a function, no local variable is created.  The -p  option  causes  the  word
              export  to  be inserted before each one.  Otherwise, the given names are marked for
              automatic export to the environment of subsequently-executed commands.

       false  Does nothing, and exits 1. Used with until for infinite loops.

       fg [ job... ]
              This command is only on systems that support job control.  Each  job  specified  is
              brought  to  the  foreground and waited for in the specified order.  Otherwise, the
              current job is brought into the foreground.  See Jobs  for  a  description  of  the
              format of job.

       getconf [ name [ pathname ] ]
              Prints  the  current  value  of  the  configuration  parameter  given by name.  The
              configuration parameters are defined by the IEEE POSIX 1003.1 and IEEE POSIX 1003.2
              standards.   (See  pathconf(2)  and sysconf(2).)  The pathname argument is required
              for parameters whose value depends on the location  in  the  file  system.   If  no
              arguments   are  given,  getconf  prints  the  names  and  values  of  the  current
              configuration parameters.  The pathname / is used for each of the  parameters  that
              requires pathname.

       getopts [  -a name ] optstring vname [ arg ... ]
              Checks  arg  for  legal  options.  If arg is omitted, the positional parameters are
              used.  An option argument begins with a + or a -.  An option not beginning  with  +
              or  -  or  the  argument  --  ends  the options.  Options beginning with + are only
              recognized when optstring begins with a +.  optstring  contains  the  letters  that
              getopts  recognizes.   If  a  letter is followed by a :, that option is expected to
              have an argument.  The options can be separated from the argument by  blanks.   The
              option  -?   causes  getopts to generate a usage message on standard error.  The -a
              argument can be used to specify the name  to  use  for  the  usage  message,  which
              defaults to $0.
              getopts  places  the next option letter it finds inside variable vname each time it
              is invoked.  The option letter will be prepended with a + when arg begins with a +.
              The  index  of the next arg is stored in OPTIND.  The option argument, if any, gets
              stored in OPTARG.
              A leading : in optstring causes getopts to store the letter of an invalid option in
              OPTARG,  and  to  set  vname  to  ?  for an unknown option and to : when a required
              option argument is missing.  Otherwise, getopts prints an error message.  The  exit
              status is non-zero when there are no more options.
              There  is  no way to specify any of the options :, +, -, ?, [, and ].  The option #
              can only be specified as the first option.

       hist [ -e ename  ] [ -nlr ] [ first [ last ] ]
       hist -s  [ old=new ] [ command ]
              In the first form, a range of commands from first to last is selected from the last
              HISTSIZE  commands  that  were typed at the terminal.  The arguments first and last
              may be specified as a number or as a string.  A string is used to locate  the  most
              recent  command  starting  with  the given string.  A negative number is used as an
              offset to the current command number.  If the -l option is selected,  the  commands
              are listed on standard output.  Otherwise, the editor program ename is invoked on a
              file containing these keyboard commands.  If ename is not supplied, then the  value
              of  the  variable  HISTEDIT  is used.  If HISTEDIT is not set, then FCEDIT (default
              /usr/bin/ex) is  used  as  the  editor.   When  editing  is  complete,  the  edited
              command(s)  is  executed if the changes have been saved.  If last is not specified,
              then it will be set to first.  If first  is  not  specified,  the  default  is  the
              previous command for editing and -16 for listing.  The option -r reverses the order
              of the commands and the option -n suppresses command numbers when listing.  In  the
              second  form,  command  is interpreted as first described above and defaults to the
              last command executed.  The  resulting  command  is  executed  after  the  optional
              substitution old=new is performed.

       jobs [ -lnp ] [ job ... ]
              Lists  information about each given job; or all active jobs if job is omitted.  The
              -l option lists process ids in addition to the normal information.  The  -n  option
              only  displays jobs that have stopped or exited since last notified.  The -p option
              causes only the process group to be listed.  See Jobs  for  a  description  of  the
              format of job.

       kill [ -s signame ] job ...
       kill [ -n signum ] job ...
       kill -Ll [ sig ... ]
              Sends  either  the TERM (terminate) signal or the specified signal to the specified
              jobs or processes.  Signals are either given by number with the  -n  option  or  by
              name  with  the  -s  option (as given in <signal.h>, stripped of the prefix ``SIG''
              with the exception that SIGCLD is named CHLD).  For backward compatibility,  the  n
              and s can be omitted and the number or name placed immediately after the -.  If the
              signal being sent is TERM (terminate) or HUP (hangup), then the job or process will
              be  sent  a  CONT  (continue) signal if it is stopped.  The argument job can be the
              process id of a process that is not a member of one of the active jobs.   See  Jobs
              for a description of the format of job.  In the third form, kill -l, or kill -L, if
              sig is not specified, the signal names are listed.  The -l  option  list  only  the
              signal  names.   -L  options  lists  each  signal  name  and  corresponding number.
              Otherwise, for each sig that is a name, the corresponding signal number is  listed.
              For  each  sig  that  is  a  number,  the  signal  name  corresponding to the least
              significant 8 bits of sig is listed.

       let arg ...
              Each arg is a separate arithmetic expression to be evaluated.  let only  recognizes
              octal constants starting with 0 when the set option letoctal is on.  See Arithmetic
              Evaluation above, for a description of arithmetic expression evaluation.
              The exit status is 0 if the value  of  the  last  expression  is  non-zero,  and  1
              otherwise.

       † newgrp [ arg ... ]
              Equivalent to exec /bin/newgrp arg ....

       print [ -CRenprsv ] [ -u unit] [ -f format ] [ arg ... ]
              With  no  options  or  with option - or --, each arg is printed on standard output.
              The -f option causes the arguments to be printed as described by printf.   In  this
              case,  any e, n, r, R options are ignored.  Otherwise, unless the -C, -R, -r, or -v
              are specified, the following escape conventions will be applied:
              \a     The alert character (ascii 07).
              \b     The backspace character (ascii 010).
              \c     Causes print to end without processing more arguments and not adding a  new-
                     line.
              \f     The formfeed character (ascii 014).
              \n     The new-line character (ascii 012).
              \r     The carriage return character (ascii 015).
              \t     The tab character (ascii 011).
              \v     The vertical tab character (ascii 013).
              \E     The escape character (ascii 033).
              \\     The backslash character \.
              \0x    The character defined by the 1, 2, or 3-digit octal string given by x.

              The  -R  option will print all subsequent arguments and options other than -n.  The
              -e causes the above  escape  conventions  to  be  applied.   This  is  the  default
              behavior.   It  reverses  the  effect  of  an earlier -r.  The -p option causes the
              arguments to be written onto the pipe of the process spawned  with  ⎪&  instead  of
              standard  output.   The -v option treats each arg as a variable name and writes the
              value in the printf %B format.  The -C option treats each arg as  a  variable  name
              and  writes the value in the printf %#B format.  The -s option causes the arguments
              to be written onto the history file instead of standard output.  The -u option  can
              be used to specify a one digit file descriptor unit number unit on which the output
              will be placed.  The default is 1.  If the option -n is used, no new-line is  added
              to the output.

       printf format [ arg ... ]
              The  arguments  arg  are  printed  on standard output in accordance with the ANSI-C
              formatting rules associated with the  format  string  format.   If  the  number  of
              arguments  exceeds the number of format specifications, the format string is reused
              to format remaining arguments.  The following extensions can also be used:
              %b     A %b format can be used instead of %s  to  cause  escape  sequences  in  the
                     corresponding arg to be expanded as described in print.
              %B     A %B option causes each of the arguments to be treated as variable names and
                     the binary value of variable will be printed.  The alternate flag # causes a
                     compound  variable  to  be output on a single line.  This is most useful for
                     compound variables and variables whose attribute is -b.
              %H     A %H format can be used instead of %s to cause characters in  arg  that  are
                     special  in  HTML  and XML to be output as their entity name.  The alternate
                     flag # formats the output for use as a URI.
              %P     A %P format can be used instead of %s to cause arg to be interpreted  as  an
                     extended regular expression and be printed as a shell pattern.
              %R     A  %R  format  can be used instead of %s to cause arg to be interpreted as a
                     shell pattern and to be printed as an extended regular expression.
              %q     A %q format can be used instead of %s to cause the resulting  string  to  be
                     quoted  in a manner than can be reinput to the shell.  When q is preceded by
                     the alternative format specifier, #, the string is quoted in manner suitable
                     as a field in a .csv format file.
              %(date-format)T
                     A  %(date-format)T  format  can  be  use to treat an argument as a date/time
                     string and to format the date/time according to the date-format  as  defined
                     for the date(1) command.
              %Z     A %Z format will output a byte whose value is 0.
              %d     The  precision field of the %d format can be followed by a .  and the output
                     base.  In this case, the # flag character causes base# to be prepended.
              #      The # flag, when used with the %d format without an  output  base,  displays
                     the output in powers of 1000 indicated by one of the following suffixes: k M
                     G T P E, and when used with the %i format displays the output in  powers  of
                     1024 indicated by one of the following suffixes: Ki Mi Gi Ti Pi Ei.
              =      The = flag centers the output within the specified field width.
              L      The  L  flag,  when  used  with  the  %c  or %s formats, treats precision as
                     character width instead of byte count.
              ,      The , flag, when used with the %d or %f formats, separates groups of  digits
                     with the grouping delimiter (, on groups of 3 in the C locale.)

       pwd [ -LP ]
              Outputs  the value of the current working directory.  The -L option is the default;
              it prints the logical name of the current directory.  If the -P  option  is  given,
              all  symbolic  links  are resolved from the name.  The last instance of -L or -P on
              the command line determines which method is used.

       read [ -ACSprsv ] [ -d delim] [ -n n] [ [ -N n] [ [ -t timeout] [ -u unit] [  vname?prompt
       ] [ vname ... ]
              The shell input mechanism.  One line is read and is broken up into fields using the
              characters in IFS as separators.  The escape character, \, is used  to  remove  any
              special  meaning  for  the next character and for line continuation.  The -d option
              causes the read to continue to the first character of delim rather  than  new-line.
              The  -n  option  causes  at most n bytes to read rather a full line but will return
              when reading from a slow device as soon as any characters have been read.   The  -N
              option  causes  exactly  n to be read unless an end-of-file has been encountered or
              the read times out because of the -t option.  In raw mode, -r, the \  character  is
              not  treated specially.  The first field is assigned to the first vname, the second
              field to the second vname, etc., with leftover fields assigned to the  last  vname.
              When  vname  has the binary attribute and -n or -N is specified, the bytes that are
              read are stored directly into the variable.  If the -v is specified, then the value
              of  the  first  vname  will be used as a default value when reading from a terminal
              device.  The -A option causes the variable vname to be unset and each field that is
              read to be stored in successive elements of the indexed array vname.  The -C option
              causes the variable vname to be read  as  a  compound  variable.   Blanks  will  be
              ignored when finding the beginning open parenthesis.  The -S option causes the line
              to be treated like a record in a .csv format file so that double quotes can be used
              to  allow  the  delimiter  character  and the new-line character to appear within a
              field.  The -p option causes the input line to be taken from the input  pipe  of  a
              process spawned by the shell using ⎪&.  If the -s option is present, the input will
              be saved as a command in the history file.  The option -u can be used to specify  a
              one  digit  file  descriptor  unit  unit  to read from.  The file descriptor can be
              opened with the exec special built-in command.  The default value of unit n  is  0.
              The  option -t is used to specify a timeout in seconds when reading from a terminal
              or pipe.  If vname is omitted, then REPLY is used as the default vname.  An end-of-
              file  with  the  -p  option  causes cleanup for this process so that another can be
              spawned.  If the first argument contains a ?, the remainder of this word is used as
              a  prompt  on  standard  error when the shell is interactive.  The exit status is 0
              unless an end-of-file is encountered or read has timed out.

       †† readonly [ -p ] [ vname[=value] ] ...
              If vname is not given, the names and values of  each  variable  with  the  readonly
              attribute  is printed with the values quoted in a manner that allows them to be re-
              inputted.  The -p option causes the word readonly to be inserted before  each  one.
              Otherwise,  the  given vnames are marked readonly and these names cannot be changed
              by subsequent assignment.  When defining a type, if the value of  a  readonly  sub-
              variable is not defined the value is required when creating each instance.

       † return [ n ]
              Causes a shell function or .  script to return to the invoking script with the exit
              status specified by n.  The value will be the  least  significant  8  bits  of  the
              specified  status.   If  n  is  omitted, then the return status is that of the last
              command executed.  If return is invoked while not in a function  or  a  .   script,
              then it behaves the same as exit.

       † set [ ±BCGabefhkmnoprstuvx ] [ ±o [ option ] ] ... [ ±A vname ]  [ arg ... ]
              The options for this command have meaning as follows:
              -A      Array  assignment.  Unset the variable vname and assign values sequentially
                      from the arg list.  If +A is used, the variable vname is not unset first.
              -B      Enable brace pattern field generation.  This is the default behavior.
              -B      Enable brace group expansion.  On by default.
              -C      Prevents redirection > from truncating  existing  files.   Files  that  are
                      created  are  opened  with the O_EXCL mode.  Requires >⎪ to truncate a file
                      when turned on.
              -G      Causes the pattern ∗∗ by itself to match files and zero or more directories
                      and sub-directories when used for file name generation.  If followed by a /
                      only directories and sub-directories are matched.
              -a      All subsequent variables that are defined are automatically exported.
              -b      Prints job completion messages as soon as a background  job  changes  state
                      rather than waiting for the next prompt.
              -e      Unless  contained  in  a  ⎪⎪  or && command, or the command following an if
                      while or until command or in the pipeline following !, if a command  has  a
                      non-zero exit status, execute the ERR trap, if set, and exit.  This mode is
                      disabled while reading profiles.
              -f      Disables file name generation.
              -h      Each command becomes a tracked alias when first encountered.
              -k      (Obsolete). All variable assignment arguments are placed in the environment
                      for a command, not just those that precede the command name.
              -m      Background  jobs will run in a separate process group and a line will print
                      upon completion.  The exit status of  background  jobs  is  reported  in  a
                      completion  message.  On systems with job control, this option is turned on
                      automatically for interactive shells.
              -n      Read commands and check them for syntax errors, but do  not  execute  them.
                      Ignored for interactive shells.
              -o      The following argument can be one of the following option names:
                      allexport
                              Same as -a.
                      errexit Same as -e.
                      bgnice  All  background  jobs  are  run  at  a lower priority.  This is the
                              default mode.
                      braceexpand
                              Same as -B.
                      emacs   Puts you in an emacs style in-line editor for command entry.
                      globstar
                              Same as -G.
                      gmacs   Puts you in a gmacs style in-line editor for command entry.
                      ignoreeof
                              The shell will not exit on end-of-file.  The command exit  must  be
                              used.
                      keyword Same as -k.
                      letoctal
                              The let command allows octal constants starting with 0.
                      markdirs
                              All  directory  names  resulting  from  file name generation have a
                              trailing / appended.
                      monitor Same as -m.
                      multiline
                              The built-in editors will use multiple  lines  on  the  screen  for
                              lines  that  are longer than the width of the screen.  This may not
                              work for all terminals.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Do not save function definitions in the history file.
                      notify  Same as -b.
                      nounset Same as -u.
                      pipefail
                              A pipeline will not complete until all components of  the  pipeline
                              have  completed, and the return value will be the value of the last
                              non-zero command to fail or zero if no command has failed.
                      showme  When enabled, simple commands or pipelines preceded by a  semicolon
                              (;) will be displayed as if the xtrace option were enabled but will
                              not be executed.  Otherwise, the leading ; will be ignored.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      trackall
                              Same as -h.
                      vi      Puts you in insert mode of a vi style in-line editor until you  hit
                              the escape character 033.  This puts you in control mode.  A return
                              sends the line.
                      viraw   Each character is processed as it is typed in vi mode.
                      xtrace  Same as -x.
                      If no option name  is  supplied,  then  the  current  option  settings  are
                      printed.
              -p      Disables   processing   of  the  $HOME/.profile  file  and  uses  the  file
                      /etc/suid_profile instead of the ENV file.  This mode is  on  whenever  the
                      effective  uid  (gid) is not equal to the real uid (gid).  Turning this off
                      causes the effective uid and gid to be set to the real uid and gid.
              -r      Enables the restricted shell.  This option cannot be unset once set.
              -s      Sort the positional parameters lexicographically.
              -t      (Obsolete).  Exit after reading and executing one command.
              -u      Treat unset parameters as an error when substituting.
              -v      Print shell input lines as they are read.
              -x      Print commands and their arguments as they are executed.
              --      Do not change any of the options; useful in setting $1 to a value beginning
                      with  -.  If no arguments follow this option then the positional parameters
                      are unset.

              As an obsolete feature, if the first arg is - then the -x and -v options are turned
              off  and  the  next  arg  is  treated as the first argument.  Using + rather than -
              causes these options to be turned  off.   These  options  can  also  be  used  upon
              invocation of the shell.  The current set of options may be found in $-.  Unless -A
              is specified, the remaining arguments are positional parameters and  are  assigned,
              in  order,  to  $1 $2 ....  If no arguments are given, then the names and values of
              all variables are printed on the standard output.

       † shift [ n ]
              The positional parameters from $n+1 ...  are renamed $1 ... , default n is 1.   The
              parameter  n  can  be  any  arithmetic  expression that evaluates to a non-negative
              number less than or equal to $#.

       sleep seconds
              Suspends execution for the number of decimal seconds or fractions of a second given
              by seconds.

       † trap [ -p ] [ action ] [ sig ] ...
              The  -p option causes the trap action associated with each trap as specified by the
              arguments to be printed  with  appropriate  quoting.   Otherwise,  action  will  be
              processed  as if it were an argument to eval when the shell receives signal(s) sig.
              Each sig can be given as a number or as the name of the signal.  Trap commands  are
              executed in order of signal number.  Any attempt to set a trap on a signal that was
              ignored on entry to the current shell is ineffective.  If action is omitted and the
              first  sig  is a number, or if action is -, then the trap(s) for each sig are reset
              to their original values.  If action is the null string then this signal is ignored
              by  the  shell  and  by the commands it invokes.  If sig is ERR then action will be
              executed whenever a command has a non-zero exit  status.   If  sig  is  DEBUG  then
              action will be executed before each command.  The variable .sh.command will contain
              the contents of the current command line when  action  is  running.   If  the  exit
              status  of  the  trap is 2 the command will not be executed.  If the exit status of
              the trap is 255 and inside a function or a dot script, the function or  dot  script
              will  return.   If  sig  is 0 or EXIT and the trap statement is executed inside the
              body of a function defined with the function name syntax, then the  command  action
              is  executed  after  the  function  completes.   If sig is 0 or EXIT for a trap set
              outside any function then the command action is executed on exit  from  the  shell.
              If  sig  is  KEYBD,  then  action  will be executed whenever a key is read while in
              emacs, gmacs, or vi mode.  The trap command with no  arguments  prints  a  list  of
              commands associated with each signal number.

       An  exit  or  return without an argument in a trap action will preserve the exit status of
       the command that invoked the trap.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       †† typeset [ ±ACHSfblmnprtux  ]  [  ±EFLRXZi[n]  ]    [  +-M   [  mapname  ]  ]  [  -T   [
       tname=(assign_list) ] ] [ -h str ] [ -a [type] ] [ vname[=value ]  ] ...
              Sets  attributes and values for shell variables and functions.  When invoked inside
              a function defined with the function name syntax, a new instance  of  the  variable
              vname  is created, and the variable's value and type are restored when the function
              completes.  The following list of attributes may be specified:
              -A     Declares vname to be an associative array.  Subscripts  are  strings  rather
                     than arithmetic expressions.
              -C     causes  each  vname  to  be  a  compound  variable.   value names a compound
                     variable it is copied into vname.  Otherwise, it unsets each vname.
              -a     Declares vname to be an indexed array.  If type is specified, it must be the
                     name  of  an  enumeration  type  created with the enum command and it allows
                     enumeration constants to be used as subscripts.
              -E     Declares vname to be a double precision floating point number.  If n is non-
                     zero,  it  defines  the  number  of  significant  figures that are used when
                     expanding vname.  Otherwise, ten significant figures will be used.
              -F     Declares vname to be a double precision floating point number.  If n is non-
                     zero,  it defines the number of places after the decimal point that are used
                     when expanding vname.  Otherwise ten places after the decimal point will  be
                     used.
              -H     This option provides UNIX to host-name file mapping on non-UNIX machines.
              -L     Left  justify  and  remove  leading blanks from value.  If n is non-zero, it
                     defines the width of the field, otherwise it is determined by the  width  of
                     the  value  of  first  assignment.   When the variable is assigned to, it is
                     filled on the right with blanks or truncated, if necessary, to fit into  the
                     field.  The -R option is turned off.
              -M     Use  the  character  mapping mapping defined by wctrans(3).  such as tolower
                     and toupper when assigning a value to each of the specified operands.   When
                     mapping is specified and there are not operands, all variables that use this
                     mapping are written to standard output.  When mapping is omitted  and  there
                     are no operands, all mapped variables are written to standard output.
              -R     Right  justify  and  fill with leading blanks.  If n is non-zero, it defines
                     the width of the field, otherwise it is determined by the width of the value
                     of first assignment.  The field is left filled with blanks or truncated from
                     the end if the variable is reassigned.  The -L option is turned off.
              -S     When used within the  assign_list  of  a  type  definition,  it  causes  the
                     specified sub-variable to be shared by all instances of the type.  When used
                     inside a function defined with the function  reserved  word,  the  specified
                     variables will have function static scope.  Otherwise, the variable is unset
                     prior to processing the assignment list.
              -T     If followed by tname, it creates a type named by tname  using  the  compound
                     assignment  assign_list  to  tname.   Otherwise,  it  writes  all  the  type
                     definitions to standard output.
              -X     Declares vname to be a double precision floating point  number  and  expands
                     using  the %a format of ISO-C99.  If n is non-zero, it defines the number of
                     hex digits after the radix point that is used  when  expanding  vname.   The
                     default is 10.
              -Z     Right  justify  and fill with leading zeros if the first non-blank character
                     is a digit and the -L option has not been set.  Remove leading zeros if  the
                     -L option is also set.  If n is non-zero, it defines the width of the field,
                     otherwise it is determined by the width of the value of first assignment.
              -f     The  names  refer  to  function  names  rather  than  variable  names.    No
                     assignments  can be made and the only other valid options are -S, -t, -u and
                     -x.  The -S can be used with discipline  functions  defined  in  a  type  to
                     indicate  that  the  function  is  static.   For a static function, the same
                     method will be used by all instances of that type no matter  which  instance
                     references  it.   In  addition,  it can only use value of variables from the
                     original type definition.  These discipline functions cannot be redefined in
                     any  type  instance.   The  -t  option  turns  on execution tracing for this
                     function.  The -u option causes this function to be marked  undefined.   The
                     FPATH  variable  will  be  searched to find the function definition when the
                     function is referenced.  If no options other than -f is specified, then  the
                     function  definition  will  be  displayed  on  standard  output.   If  +f is
                     specified, then a line containing the function  name  followed  by  a  shell
                     comment  containing  the  line  number  and path name of the file where this
                     function was defined, if any, is displayed.  The exit status can be used  to
                     determine  whether  the function is defined so that typeset -f .sh.math.name
                     will return 0 when math function name is defined and non-zero otherwise.
              -b     The variable can hold any number of bytes of data.  The data can be text  or
                     binary.  The value is represented by the base64 encoding of the data.  If -Z
                     is also specified, the size in bytes of the  data  in  the  buffer  will  be
                     determined  by  the  size  associated  with  the  -Z.   If the base64 string
                     assigned results in more data, it will be truncated.  Otherwise, it will  be
                     filled  with bytes whose value is zero.  The printf format %B can be used to
                     output the actual data in this buffer instead of the base64 encoding of  the
                     data.
              -h     Used  within type definitions to add information when generating information
                     about the sub-variable on the man page.  It is ignored when used outside  of
                     a type definition.  When used with -f the information is associated with the
                     corresponding discipline function.
              -i     Declares vname to be represented internally as integer.  The right hand side
                     of  an assignment is evaluated as an arithmetic expression when assigning to
                     an integer.  If n is  non-zero,  it  defines  the  output  arithmetic  base,
                     otherwise the output base will be ten.
              -l     Used with -i, -E or -F, to indicate long integer, or long float.  Otherwise,
                     all upper-case characters  are  converted  to  lower-case.   The  upper-case
                     option, -u, is turned off.  Equivalent to -M tolower .
              -m     moves  or  renames  the variable.  The value is the name of a variable whose
                     value will be moved to vname.  The original variable will be unset.   Cannot
                     be used with any other options.
              -n     Declares  vname  to  be a reference to the variable whose name is defined by
                     the value of variable vname.  This is usually used to reference  a  variable
                     inside a function whose name has been passed as an argument.  Cannot be used
                     with any other options.
              -p     The name, attributes and values for the given vnames are written on standard
                     output  in a form that can be used as shell input.  If +p is specified, then
                     the values are not displayed.
              -r     The given vnames are marked readonly and these names cannot  be  changed  by
                     subsequent assignment.
              -t     Tags  the variables.  Tags are user definable and have no special meaning to
                     the shell.
              -u     When given along with -i, specifies unsigned integer.  Otherwise, all lower-
                     case  characters are converted to upper-case.  The lower-case option, -l, is
                     turned off.  Equivalent to -M toupper .
              -x     The given vnames are marked for  automatic  export  to  the  environment  of
                     subsequently-executed  commands.   Variables whose names contain a .  cannot
                     be exported.

              The -i attribute cannot be specified along with -R, -L, -Z, or -f.

              Using + rather than - causes these options to be turned off.  If no vname arguments
              are  given,  a  list  of  vnames  (and  optionally  the values) of the variables is
              printed.  (Using + rather than - keeps the values  from  being  printed.)   The  -p
              option causes typeset followed by the option letters to be printed before each name
              rather than the names of the options.  If any option other than -p is  given,  only
              those  variables  which  have all of the given options are printed.  Otherwise, the
              vnames and attributes of all variables that have attributes are printed.

       ulimit [ -HSacdfmnpstv ] [ limit ]
              Set or display a resource limit.  The available resource limits are  listed  below.
              Many systems do not support one or more of these limits.  The limit for a specified
              resource is set when limit is specified.  The value of limit can be a number in the
              unit  specified  below  with  each resource, or the value unlimited.  The -H and -S
              options specify whether the hard limit or the soft limit for the given resource  is
              set.   A  hard  limit  cannot  be  increased  once  it is set.  A soft limit can be
              increased up to the value of the hard limit.  If neither the  H  nor  S  option  is
              specified,  the  limit applies to both.  The current resource limit is printed when
              limit is omitted.  In this case, the soft limit is printed unless H  is  specified.
              When  more  than one resource is specified, then the limit name and unit is printed
              before the value.
              -a     Lists all of the current resource limits.
              -c     The number of 512-byte blocks on the size of core dumps.
              -d     The number of K-bytes on the size of the data area.
              -f     The number of 512-byte blocks on files that can be written  by  the  current
                     process or by child processes (files of any size may be read).
              -m     The number of K-bytes on the size of physical memory.
              -n     The number of file descriptors plus 1.
              -p     The number of 512-byte blocks for pipe buffering.
              -s     The number of K-bytes on the size of the stack area.
              -t     The number of CPU seconds to be used by each process.
              -v     The number of K-bytes for virtual memory.

              If no option is given, -f is assumed.

       umask [ -S ] [ mask ]
              The  user  file-creation mask is set to mask (see umask(2)).  mask can either be an
              octal number or a symbolic value as described in chmod(1).  If a symbolic value  is
              given,  the new umask value is the complement of the result of applying mask to the
              complement of the previous umask value.  If mask is omitted, the current  value  of
              the  mask  is  printed.   The -S option causes the mode to be printed as a symbolic
              value.  Otherwise, the mask is printed in octal.

       † unalias [ -a ] name ...
              The aliases given by the list of names are removed from the  alias  list.   The  -a
              option causes all the aliases to be unset.

       †unset [ -fnv ] vname ...
              The  variables  given  by  the list of vnames are unassigned, i.e., except for sub-
              variables within a type, their values and attributes are erased.  For sub-variables
              of  a  type,  the  values  are reset to the default value from the type definition.
              Readonly variables cannot be unset.  If the -f option is set, then the names  refer
              to  function  names.   If  the  -v  option is set, then the names refer to variable
              names.  The -f option overrides -v.  If -n is set and name  is  a  name  reference,
              then  name  will be unset rather than the variable that it references.  The default
              is equivalent to -v.  Unsetting LINENO, MAILCHECK, OPTARG, OPTIND, RANDOM, SECONDS,
              TMOUT,  and  _ removes their special meaning even if they are subsequently assigned
              to.

       wait [ job ... ]
              Wait for the specified job and report its termination status.  If job is not given,
              then  all  currently  active  child processes are waited for.  The exit status from
              this command is that of the last process waited for if job is specified;  otherwise
              it is zero.  See Jobs for a description of the format of job.

       whence [ -afpv ] name ...
              For each name, indicate how it would be interpreted if used as a command name.
              The  -v  option produces a more verbose report.  The -f option skips the search for
              functions.  The -p option does a path search for name even if name is an  alias,  a
              function,  or  a  reserved  word.   The  -p option turns off the -v option.  The -a
              option is similar to the -v option but causes all interpretations of the given name
              to be reported.

   Invocation.
       If  the  shell  is invoked by exec(2), and the first character of argument zero ($0) is -,
       then the shell is assumed to be a login shell and commands are read from /etc/profile  and
       then  from  either  .profile  in  the  current directory or $HOME/.profile, if either file
       exists.  Next, for interactive shells, commands are read from the file named by performing
       parameter expansion, command substitution, and arithmetic substitution on the value of the
       environment variable ENV if the file exists.  If the -s option is not present and arg  and
       a  file  by the name of arg exists, then it reads and executes this script.  Otherwise, if
       the first arg does not contain a /, a path  search  is  performed  on  the  first  arg  to
       determine  the name of the script to execute.  The script arg must have execute permission
       and any setuid and setgid settings will be ignored.  If the script is  not  found  on  the
       path,  arg  is processed as if it named a built-in command or function.  Commands are then
       read as described below; the following options are interpreted by the  shell  when  it  is
       invoked:

       -D      Do not execute the script, but output the set of double quoted strings preceded by
               a $.  These strings are  needed  for  localization  of  the  script  to  different
               locales.
       -E      Reads  the  file named by the ENV variable or by $HOME/.kshrc if not defined after
               the profiles.
       -c        If the -c option is present, then commands are read from  the  first  arg.   Any
                 remaining arguments become positional parameters starting at 0.
       -s        If  the  -s  option is present or if no arguments remain, then commands are read
                 from the standard input.  Shell output, except for the  output  of  the  Special
                 Commands listed above, is written to file descriptor 2.
       -i        If  the  -i option is present or if the shell input and output are attached to a
                 terminal (as told by tcgetattr(2)), then this shell  is  interactive.   In  this
                 case  TERM  is  ignored  (so that kill 0 does not kill an interactive shell) and
                 INTR is caught and ignored (so that wait is ).  In all cases, QUIT is ignored by
                 the shell.
       -r        If the -r option is present, the shell is a restricted shell.
       -D        A  list of all double quoted strings that are preceded by a $ will be printed on
                 standard output and the shell will exit.  This set of strings will be subject to
                 language  translation  when  the  locale is not C or POSIX.  No commands will be
                 executed.
       -R filename
                 The -R filename option is used to generate a cross reference database  that  can
                 be  used  by a separate utility to find definitions and references for variables
                 and commands.
       The remaining options and arguments  are  described  under  the  set  command  above.   An
       optional - as the first argument is ignored.
   Rksh Only.
       Rksh  is used to set up login names and execution environments whose capabilities are more
       controlled than those of the standard shell.  The actions of rksh are identical  to  those
       of ksh, except that the following are disallowed:
              Unsetting the restricted option.
              changing directory (see cd(1)),
              setting or unsetting the value or attributes of SHELL, ENV, FPATH, or PATH,
              specifying path or command names containing /,
              redirecting output (>, >|, <>, and >>).
              adding or deleting built-in commands.
              using command -p to invoke a command.

       The restrictions above are enforced after .profile and the ENV files are interpreted.

       When  a  command  to  be  executed  is  found to be a shell procedure, rksh invokes ksh to
       execute it.  Thus, it is possible to provide to the end-user shell  procedures  that  have
       access to the full power of the standard shell, while imposing a limited menu of commands;
       this scheme assumes that the end-user does not have write and execute permissions  in  the
       same directory.

       The net effect of these rules is that the writer of the .profile has complete control over
       user actions,  by  performing  guaranteed  setup  actions  and  leaving  the  user  in  an
       appropriate directory (probably not the login directory).

       The  system administrator often sets up a directory of commands (e.g., /usr/rbin) that can
       be safely invoked by rksh.

EXIT STATUS

       Errors detected by the shell, such as syntax errors, cause the shell to return a  non-zero
       exit  status.   If  the shell is being used non-interactively, then execution of the shell
       file is abandoned unless the error occurs inside a subshell in which case the subshell  is
       abandoned.  Otherwise, the shell returns the exit status of the last command executed (see
       also the exit command above).  Run time errors detected  by  the  shell  are  reported  by
       printing  the  command  or function name and the error condition.  If the line number that
       the error occurred on is greater than one, then the line number is also printed in  square
       brackets ([]) after the command or function name.

FILES

       /etc/profile
              The system wide initialization file, executed for login shells.

       $HOME/.profile
              The personal initialization file, executed for login shells after /etc/profile.

       $HOME/.kshrc
              Default  personal  initialization file, executed for interactive shells when ENV is
              not set.

       /etc/suid_profile
              Alternative initialization file, executed instead of  the  personal  initialization
              file when the real and effective user or group id do not match.

       /dev/null
              NULL device

SEE ALSO

       cat(1),  cd(1), chmod(1), cut(1), egrep(1), echo(1), emacs(1), env(1), fgrep(1), gmacs(1),
       grep(1),  newgrp(1),  stty(1),  test(1),  umask(1),  vi(1),  dup(2),   exec(2),   fork(2),
       getpwnam(3),  ioctl(2),  lseek(2),  paste(1),  pathconf(2), pipe(2), sysconf(2), umask(2),
       ulimit(2), wait(2), wctrans(3), rand(3), a.out(5), profile(5), environ(7).

       Morris I. Bolsky and David G. Korn, The New KornShell Command  and  Programming  Language,
       Prentice Hall, 1995.

       POSIX - Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2, IEEE, 1993.

CAVEATS

       If  a  command  is  executed,  and  then  a  command  with the same name is installed in a
       directory in the search path before the directory where the original  command  was  found,
       the  shell  will  continue  to  exec the original command.  Use the -t option of the alias
       command to correct this situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe character .

       Using the hist built-in command within a compound command will cause the whole command  to
       disappear from the history file.

       The  built-in  command  .  file  reads  the  whole  file before any commands are executed.
       Therefore, alias and unalias commands in the file will not apply to any  commands  defined
       in the file.

       Traps  are not processed while a job is waiting for a foreground process.  Thus, a trap on
       CHLD won't be executed until the foreground job terminates.

       It is a good idea to leave a space after the comma operator in arithmetic  expressions  to
       prevent  the  comma  from  being  interpreted  as  the  decimal point character in certain
       locales.

                                                                                           KSH(1)