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NAME

       ed - edit text

SYNOPSIS

       ed [-p string][-s][file]

DESCRIPTION

       The  ed utility is a line-oriented text editor that uses two modes: command mode and input
       mode. In command mode the input characters shall be interpreted as commands, and in  input
       mode they shall be interpreted as text. See the EXTENDED DESCRIPTION section.

OPTIONS

       The  ed  utility  shall  conform  to  the Base Definitions volume of IEEE Std 1003.1-2001,
       Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -p  string
              Use string as the prompt string when in command mode. By default, there shall be no
              prompt string.

       -s     Suppress  the  writing  of  byte  counts  by e, E, r, and w commands and of the '!'
              prompt after a !command.

OPERANDS

       The following operand shall be supported:

       file   If the file argument is given, ed shall simulate an e command on the file named  by
              the  pathname, file, before accepting commands from the standard input. If the file
              operand is '-' , the results are unspecified.

STDIN

       The standard input shall be a text file  consisting  of  commands,  as  described  in  the
       EXTENDED DESCRIPTION section.

INPUT FILES

       The input files shall be text files.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of ed:

       HOME   Determine the pathname of the user's home directory.

       LANG   Provide  a  default  value for the internationalization variables that are unset or
              null. (See the  Base  Definitions  volume  of  IEEE Std 1003.1-2001,  Section  8.2,
              Internationalization Variables for the precedence of internationalization variables
              used to determine the values of locale categories.)

       LC_ALL If set to  a  non-empty  string  value,  override  the  values  of  all  the  other
              internationalization variables.

       LC_COLLATE

              Determine  the  locale  for the behavior of ranges, equivalence classes, and multi-
              character collating elements within regular expressions.

       LC_CTYPE
              Determine the locale for the interpretation of sequences of bytes of text  data  as
              characters  (for  example,  single-byte  as  opposed  to  multi-byte  characters in
              arguments and input files) and the behavior of  character  classes  within  regular
              expressions.

       LC_MESSAGES
              Determine  the  locale  that  should  be  used to affect the format and contents of
              diagnostic messages written to standard error and informative messages  written  to
              standard output.

       NLSPATH
              Determine the location of message catalogs for the processing of LC_MESSAGES .

ASYNCHRONOUS EVENTS

       The ed utility shall take the standard action for all signals (see the ASYNCHRONOUS EVENTS
       section in Utility Description Defaults ) with the following exceptions:

       SIGINT The ed utility shall interrupt its current activity,  write  the  string  "?\n"  to
              standard output, and return to command mode (see the EXTENDED DESCRIPTION section).

       SIGHUP If  the  buffer  is  not empty and has changed since the last write, the ed utility
              shall attempt to write a copy of the buffer in a file. First, the file named ed.hup
              in the current directory shall be used; if that fails, the file named ed.hup in the
              directory named by the HOME environment variable shall be used. In any case, the ed
              utility shall exit without returning to command mode.

       SIGQUIT
              The ed utility shall ignore this event.

STDOUT

       Various  editing  commands and the prompting feature (see -p) write to standard output, as
       described in the EXTENDED DESCRIPTION section.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       The output files shall be text files whose formats are dependent on the  editing  commands
       given.

EXTENDED DESCRIPTION

       The ed utility shall operate on a copy of the file it is editing; changes made to the copy
       shall have no effect on the file until a w (write) command is given. The copy of the  text
       is called the buffer.

       Commands  to  ed have a simple and regular structure: zero, one, or two addresses followed
       by a single-character command, possibly followed by  parameters  to  that  command.  These
       addresses  specify  one or more lines in the buffer. Every command that requires addresses
       has default addresses, so that the addresses very often can be omitted. If the  -p  option
       is specified, the prompt string shall be written to standard output before each command is
       read.

       In general, only one command can appear on a line.  Certain  commands  allow  text  to  be
       input.  This  text is placed in the appropriate place in the buffer. While ed is accepting
       text, it is said to be in input mode. In this mode, no commands shall be  recognized;  all
       input  is  merely collected. Input mode is terminated by entering a line consisting of two
       characters: a period ( '.' ) followed by a <newline>. This line is not considered part  of
       the input text.

   Regular Expressions in ed
       The  ed  utility  shall  support  basic  regular  expressions,  as  described  in the Base
       Definitions volume of IEEE Std 1003.1-2001, Section 9.3, Basic Regular Expressions.  Since
       regular  expressions  in  ed  are  always  matched  against  single  lines  (excluding the
       terminating <newline>s), never against any larger section of text, there is no way  for  a
       regular expression to match a <newline>.

       A null RE shall be equivalent to the last RE encountered.

       Regular  expressions  are  used  in  addresses to specify lines, and in some commands (for
       example, the s substitute command) to specify portions of a line to be substituted.

   Addresses in ed
       Addressing in ed relates to the current line. Generally, the current line is the last line
       affected  by a command. The current line number is the address of the current line. If the
       edit buffer is not empty, the initial value for the current line shall be the last line in
       the edit buffer; otherwise, zero.

       Addresses shall be constructed as follows:

        1. The period character ( '.' ) shall address the current line.

        2. The dollar sign character ( '$' ) shall address the last line of the edit buffer.

        3. The positive decimal number n shall address the nth line of the edit buffer.

        4. The  apostrophe-x  character pair ( "'x" ) shall address the line marked with the mark
           name character x, which shall be a lowercase letter from the portable  character  set.
           It  shall  be an error if the character has not been set to mark a line or if the line
           that was marked is not currently present in the edit buffer.

        5. A BRE enclosed by slash characters ( '/' ) shall  address  the  first  line  found  by
           searching forwards from the line following the current line toward the end of the edit
           buffer and stopping at the first line for which the  line  excluding  the  terminating
           <newline>  matches  the  BRE.  The BRE consisting of a null BRE delimited by a pair of
           slash characters shall address  the  next  line  for  which  the  line  excluding  the
           terminating  <newline> matches the last BRE encountered. In addition, the second slash
           can be omitted at the end of a command line. Within the BRE, a backslash-slash pair  (
           "\/" ) shall represent a literal slash instead of the BRE delimiter. If necessary, the
           search shall wrap around to the beginning  of  the  buffer  and  continue  up  to  and
           including the current line, so that the entire buffer is searched.

        6. A  BRE enclosed by question-mark characters ( '?' ) shall address the first line found
           by searching backwards from the line preceding the current line toward  the  beginning
           of  the  edit  buffer  and stopping at the first line for which the line excluding the
           terminating <newline> matches the BRE. The BRE consisting of a null BRE delimited by a
           pair  of  question-mark  characters ( "??" ) shall address the previous line for which
           the line excluding the terminating <newline> matches  the  last  BRE  encountered.  In
           addition, the second question-mark can be omitted at the end of a command line. Within
           the BRE, a backslash-question-mark pair ( "\?" ) shall represent  a  literal  question
           mark  instead  of the BRE delimiter. If necessary, the search shall wrap around to the
           end of the buffer and continue up to and including  the  current  line,  so  that  the
           entire buffer is searched.

        7. A  plus-sign  (  '+'  ) or hyphen character ( '-' ) followed by a decimal number shall
           address the current line plus or minus the number. A plus-sign or hyphen character not
           followed by a decimal number shall address the current line plus or minus 1.

       Addresses  can  be followed by zero or more address offsets, optionally <blank>-separated.
       Address offsets are constructed as follows:

        * A plus-sign or hyphen character followed by a decimal number  shall  add  or  subtract,
          respectively,  the  indicated  number  of  lines to or from the address. A plus-sign or
          hyphen character not followed by a decimal number shall add or subtract 1  to  or  from
          the address.

        * A decimal number shall add the indicated number of lines to the address.

       It shall not be an error for an intermediate address value to be less than zero or greater
       than the last line in the edit buffer. It shall be an error for the final address value to
       be  less  than zero or greater than the last line in the edit buffer. It shall be an error
       if a search for a BRE fails to find a matching line.

       Commands accept zero, one, or two addresses. If more than the required number of addresses
       are  provided  to a command that requires zero addresses, it shall be an error. Otherwise,
       if more than the required number of addresses are provided to  a  command,  the  addresses
       specified  first  shall  be evaluated and then discarded until the maximum number of valid
       addresses remain, for the specified command.

       Addresses shall be separated from each other by a comma ( ',' ) or semicolon  character  (
       ';'  ). In the case of a semicolon separator, the current line ( '.' ) shall be set to the
       first address, and only then will the second address be calculated. This  feature  can  be
       used  to determine the starting line for forwards and backwards searches; see rules 5. and
       6.

       Addresses can be omitted on either side of the comma or semicolon separator, in which case
       the resulting address pairs shall be as follows:

                                        Specified   Resulting
                                        ,           1 , $
                                        , addr      1 , addr
                                        addr ,      addr , addr
                                        ;           . ; $
                                        ; addr      . ; addr
                                        addr ;      addr ; addr

       Any  <blank>s  included between addresses, address separators, or address offsets shall be
       ignored.

   Commands in ed
       In the following list of ed commands, the default addresses are shown in parentheses.  The
       number  of addresses shown in the default shall be the number expected by the command. The
       parentheses are not part of the address; they  show  that  the  given  addresses  are  the
       default.

       It  is  generally  invalid  for  more  than one command to appear on a line.  However, any
       command (except e, E, f, q, Q, r, w, and !) can be suffixed by the letter l, n, or  p;  in
       which  case,  except  for the l, n, and p commands, the command shall be executed and then
       the new current line shall be written as described below under the l, n, and  p  commands.
       When  an  l, n, or p suffix is used with an l, n, or p command, the command shall write to
       standard output as described below, but it is unspecified whether the  suffix  writes  the
       current  line  again  in  the  requested  format  or whether the suffix has no effect. For
       example, the pl command (base p command with an l suffix)  shall  either  write  just  the
       current line or write it twice-once as specified for p and once as specified for l.  Also,
       the g, G, v, and V commands shall take a command as a parameter.

       Each address component can be preceded by zero or more <blank>s. The command letter can be
       preceded  by  zero  or  more  <blank>s.  If  a  suffix  letter ( l, n, or p) is given, the
       application shall ensure that it immediately follows the command.

       The e, E, f, r, and w commands shall take an optional file parameter, separated  from  the
       command letter by one or more <blank>s.

       If  changes  have  been  made in the buffer since the last w command that wrote the entire
       buffer, ed shall warn the user if an attempt is made to destroy the editor buffer via  the
       e or q commands. The ed utility shall write the string:

              "?\n"

       (followed  by  an  explanatory message if help mode has been enabled via the H command) to
       standard output and shall continue in command mode with the current line number unchanged.
       If the e or q command is repeated with no intervening command, it shall take effect.

       If a terminal disconnect is detected:

        * If  the  buffer is not empty and has changed since the last write, the ed utility shall
          attempt to write a copy of the buffer to a file named ed.hup in the current  directory.
          If  this  write  fails,  ed  shall  attempt to write a copy of the buffer to a filename
          ed.hup in the directory named by the HOME environment variable. If both these  attempts
          fail, ed shall exit without saving the buffer.

        * The  ed utility shall not write the file to the currently remembered pathname or return
          to command mode, and shall terminate with a non-zero exit status.

       If an end-of-file is detected on standard input:

        * If the ed utility is in input mode, ed shall terminate input mode and return to command
          mode.  It  is unspecified if any partially entered lines (that is, input text without a
          terminating <newline>) are discarded from the input text.

        * If the ed utility is in command mode, it shall act as if a q command had been entered.

       If the closing delimiter of an RE or of a replacement string (for example, '/' ) in  a  g,
       G,  s,  v, or V command would be the last character before a <newline>, that delimiter can
       be omitted, in which case the addressed line shall be written. For example, the  following
       pairs of commands are equivalent:

              s/s1/s2   s/s1/s2/p
              g/s1      g/s1/p
              ?s1       ?s1?

       If an invalid command is entered, ed shall write the string:

              "?\n"

       (followed  by  an  explanatory message if help mode has been enabled via the H command) to
       standard output and shall continue in command mode with the current line number unchanged.

   Append Command
       Synopsis:

              (.)a
              <text>
              .

       The a command shall read the given text and  append  it  after  the  addressed  line;  the
       current  line  number shall become the address of the last inserted line or, if there were
       none, the addressed line. Address 0 shall be valid for this command; it  shall  cause  the
       appended text to be placed at the beginning of the buffer.

   Change Command
       Synopsis:

              (.,.)c
              <text>
              .

       The c command shall delete the addressed lines, then accept input text that replaces these
       lines; the current line shall be set to the address of the last line input; or,  if  there
       were  none,  at the line after the last line deleted; if the lines deleted were originally
       at the end of the buffer, the current line number shall be set to the address of  the  new
       last line; if no lines remain in the buffer, the current line number shall be set to zero.
       Address 0 shall be valid for this command; it shall be interpreted as if  address  1  were
       specified.

   Delete Command
       Synopsis:

              (.,.)d

       The  d  command shall delete the addressed lines from the buffer.  The address of the line
       after the last line deleted shall become the current line number;  if  the  lines  deleted
       were  originally  at  the  end  of the buffer, the current line number shall be set to the
       address of the new last line; if no lines remain in the buffer, the  current  line  number
       shall be set to zero.

   Edit Command
       Synopsis:

              e [file]

       The  e  command  shall  delete the entire contents of the buffer and then read in the file
       named by the pathname file.  The current line number shall be set to the  address  of  the
       last  line  of  the buffer. If no pathname is given, the currently remembered pathname, if
       any, shall be used (see the f command).  The number of bytes  read  shall  be  written  to
       standard output, unless the -s option was specified, in the following format:

              "%d\n", <number of bytes read>

       The  name file shall be remembered for possible use as a default pathname in subsequent e,
       E, r, and w commands. If file is replaced by '!' , the rest of the line shall be taken  to
       be a shell command line whose output is to be read. Such a shell command line shall not be
       remembered as the current file. All marks shall be discarded  upon  the  completion  of  a
       successful  e command. If the buffer has changed since the last time the entire buffer was
       written, the user shall be warned, as described previously.

   Edit Without Checking Command
       Synopsis:

              E [file]

       The E command shall possess all properties and restrictions of the e command  except  that
       the  editor  shall not check to see whether any changes have been made to the buffer since
       the last w command.

   Filename Command
       Synopsis:

              f [file]

       If file is given, the f command shall change the currently remembered  pathname  to  file;
       whether  the  name  is  changed  or  not, it shall then write the (possibly new) currently
       remembered pathname to the standard output in the following format:

              "%s\n", <pathname>

       The current line number shall be unchanged.

   Global Command
       Synopsis:

              (1,$)g/RE/command list

       In the g command, the first step shall be to mark every line for which the line  excluding
       the  terminating  <newline>  matches  the  given  RE.  Then,  going  sequentially from the
       beginning of the file to the end of the file, the given command list shall be executed for
       each  marked  line, with the current line number set to the address of that line. Any line
       modified by the command list shall be unmarked. When the g command completes, the  current
       line  number  shall  have  the  value assigned by the last command in the command list. If
       there were no matching lines, the current line number  shall  not  be  changed.  A  single
       command  or  the  first  of a list of commands shall appear on the same line as the global
       command. All lines of a multi-line list except  the  last  line  shall  be  ended  with  a
       backslash  preceding  the  terminating  <newline>; the a, i, and c commands and associated
       input are permitted. The '.'  terminating input mode can be omitted if  it  would  be  the
       last line of the command list. An empty command list shall be equivalent to the p command.
       The use of the g, G, v, V, and ! commands in the command list produces undefined  results.
       Any  character  other  than <space> or <newline> can be used instead of a slash to delimit
       the RE. Within the RE, the RE delimiter itself can be used as a literal character if it is
       preceded by a backslash.

   Interactive Global Command
       Synopsis:

              (1,$)G/RE/

       In  the G command, the first step shall be to mark every line for which the line excluding
       the terminating <newline> matches the given RE. Then, for every such line, that line shall
       be  written, the current line number shall be set to the address of that line, and any one
       command (other than one of the a, c, i, g, G,  v,  and  V  commands)  shall  be  read  and
       executed.  A  <newline>  shall act as a null command (causing no action to be taken on the
       current line); an '&' shall cause the re-execution of the  most  recent  non-null  command
       executed  within  the current invocation of G. Note that the commands input as part of the
       execution of the G command can address and affect  any  lines  in  the  buffer.  Any  line
       modified  by  the  command  shall  be unmarked. The final value of the current line number
       shall be the value set by the last command successfully  executed.  (Note  that  the  last
       command successfully executed shall be the G command itself if a command fails or the null
       command is specified.) If there were no matching lines, the current line number shall  not
       be  changed.  The G command can be terminated by a SIGINT signal. Any character other than
       <space> or <newline> can be used instead of a slash to delimit the RE and the replacement.
       Within  the  RE,  the  RE  delimiter  itself  can  be used as a literal character if it is
       preceded by a backslash.

   Help Command
       Synopsis:

              h

       The h command shall write a short message to standard output that explains the reason  for
       the most recent '?'  notification. The current line number shall be unchanged.

   Help-Mode Command
       Synopsis:

              H

       The  H  command  shall cause ed to enter a mode in which help messages (see the h command)
       shall be written to standard output for all subsequent '?' notifications.  The  H  command
       alternately  shall  turn  this  mode  on and off; it is initially off. If the help-mode is
       being turned on, the H command also explains the previous '?' notification, if  there  was
       one. The current line number shall be unchanged.

   Insert Command
       Synopsis:

              (.)i
              <text>
              .

       The  i  command shall insert the given text before the addressed line; the current line is
       set to the last inserted line or, if there was none, to the addressed line.  This  command
       differs  from  the  a  command only in the placement of the input text. Address 0 shall be
       valid for this command; it shall be interpreted as if address 1 were specified.

   Join Command
       Synopsis:

              (.,.+1)j

       The j command shall join contiguous lines  by  removing  the  appropriate  <newline>s.  If
       exactly  one  address  is  given,  this command shall do nothing. If lines are joined, the
       current line number shall be set to the address of the joined line; otherwise, the current
       line number shall be unchanged.

   Mark Command
       Synopsis:

              (.)kx

       The  k  command  shall  mark  the  addressed line with name x, which the application shall
       ensure is a lowercase letter from the portable character set. The address "'x" shall  then
       refer to this line; the current line number shall be unchanged.

   List Command
       Synopsis:

              (.,.)l

       The l command shall write to standard output the addressed lines in a visually unambiguous
       form. The characters listed in the Base Definitions volume of IEEE Std 1003.1-2001,  Table
       5-1,  Escape  Sequences and Associated Actions ( '\\' , '\a' , '\b' , '\f' , '\r' , '\t' ,
       '\v' ) shall be written as the corresponding escape sequence; the '\n' in  that  table  is
       not  applicable.  Non-printable characters not in the table shall be written as one three-
       digit octal number (with a preceding backslash character) for each byte in  the  character
       (most  significant  byte  first). If the size of a byte on the system is greater than nine
       bits, the format used for non-printable characters is implementation-defined.

       Long lines shall be folded, with the point of folding indicated by <newline> preceded by a
       backslash;  the  length  at which folding occurs is unspecified, but should be appropriate
       for the output device. The end of each  line  shall  be  marked  with  a  '$'  ,  and  '$'
       characters  within  the text shall be written with a preceding backslash. An l command can
       be appended to any other command other than e, E, f, q, Q, r, w, or !.  The  current  line
       number shall be set to the address of the last line written.

   Move Command
       Synopsis:

              (.,.)maddress

       The  m  command  shall reposition the addressed lines after the line addressed by address.
       Address 0 shall be valid for address and cause the addressed lines  to  be  moved  to  the
       beginning of the buffer. It shall be an error if address address falls within the range of
       moved lines. The current line number shall be set to the address of the last line moved.

   Number Command
       Synopsis:

              (.,.)n

       The n command shall write to standard output the addressed lines, preceding each  line  by
       its  line  number  and a <tab>; the current line number shall be set to the address of the
       last line written. The n command can be appended to any command other than e, E, f, q,  Q,
       r, w, or !.

   Print Command
       Synopsis:

              (.,.)p

       The  p command shall write to standard output the addressed lines; the current line number
       shall be set to the address of the last line written. The p command can be appended to any
       command other than e, E, f, q, Q, r, w, or !.

   Prompt Command
       Synopsis:

              P

       The  P  command  shall  cause  ed  to prompt with an asterisk ( '*' ) (or string, if -p is
       specified) for all subsequent commands. The P command alternatively shall turn  this  mode
       on  and  off;  it shall be initially on if the -p option is specified; otherwise, off. The
       current line number shall be unchanged.

   Quit Command
       Synopsis:

              q

       The q command shall cause ed to exit. If the buffer has changed since the  last  time  the
       entire buffer was written, the user shall be warned, as described previously.

   Quit Without Checking Command
       Synopsis:

              Q

       The  Q  command  shall cause ed to exit without checking whether changes have been made in
       the buffer since the last w command.

   Read Command
       Synopsis:

              ($)r [file]

       The r command shall read in the file named by the pathname file and append  it  after  the
       addressed  line.  If no file argument is given, the currently remembered pathname, if any,
       shall be used (see the e and f commands).  The currently remembered pathname shall not  be
       changed  unless  there is no remembered pathname. Address 0 shall be valid for r and shall
       cause the file to be read at the beginning of the buffer. If the read is  successful,  and
       -s  was not specified, the number of bytes read shall be written to standard output in the
       following format:

              "%d\n", <number of bytes read>

       The current line number shall be set to the address of the last line read in. If  file  is
       replaced  by  '!'  ,  the rest of the line shall be taken to be a shell command line whose
       output is to be read. Such a shell command line shall not be  remembered  as  the  current
       pathname.

   Substitute Command
       Synopsis:

              (.,.)s/RE/replacement/flags

       The  s  command shall search each addressed line for an occurrence of the specified RE and
       replace either the first or all (non-overlapped) matched strings with the replacement; see
       the  following  description  of  the g suffix. It is an error if the substitution fails on
       every addressed line. Any character other than <space> or <newline> can be used instead of
       a  slash to delimit the RE and the replacement. Within the RE, the RE delimiter itself can
       be used as a literal character if it is preceded by a backslash. The current line shall be
       set to the address of the last line on which a substitution occurred.

       An ampersand ( '&' ) appearing in the replacement shall be replaced by the string matching
       the RE on the current line. The special meaning of '&' in this context can  be  suppressed
       by  preceding it by backslash. As a more general feature, the characters '\n' , where n is
       a digit, shall be replaced  by  the  text  matched  by  the  corresponding  back-reference
       expression.  When  the  character  '%'  is  the  only  character  in  the replacement, the
       replacement used in the most recent substitute command shall be used as the replacement in
       the  current  substitute  command; if there was no previous substitute command, the use of
       '%' in this manner shall be an error. The '%' shall lose its special meaning when it is in
       a  replacement  string  of more than one character or is preceded by a backslash. For each
       backslash ( '\' ) encountered in scanning replacement from beginning to end, the following
       character  shall lose its special meaning (if any). It is unspecified what special meaning
       is given to any character other than '&' , '\' , '%' , or digits.

       A line can be split by substituting a <newline> into it. The application shall  ensure  it
       escapes  the  <newline> in the replacement by preceding it by backslash. Such substitution
       cannot be done as part of a g or v command list. The current line number shall be  set  to
       the  address  of the last line on which a substitution is performed. If no substitution is
       performed, the current line number shall be unchanged.  If a line is split, a substitution
       shall  be  considered  to  have been performed on each of the new lines for the purpose of
       determining the new current line number. A substitution shall be considered to  have  been
       performed even if the replacement string is identical to the string that it replaces.

       The application shall ensure that the value of flags is zero or more of:

       count  Substitute for the countth occurrence only of the RE found on each addressed line.

       g      Globally  substitute  for  all non-overlapping instances of the RE rather than just
              the first one. If both g and count are specified, the results are unspecified.

       l      Write to standard output the final line in which a substitution was made. The  line
              shall be written in the format specified for the l command.

       n      Write  to standard output the final line in which a substitution was made. The line
              shall be written in the format specified for the n command.

       p      Write to standard output the final line in which a substitution was made. The  line
              shall be written in the format specified for the p command.

   Copy Command
       Synopsis:

              (.,.)taddress

       The  t  command  shall be equivalent to the m command, except that a copy of the addressed
       lines shall be placed after address address (which can be  0);  the  current  line  number
       shall be set to the address of the last line added.

   Undo Command
       Synopsis:

              u

       The  u  command shall nullify the effect of the most recent command that modified anything
       in the buffer, namely the most recent a, c, d, g, i, j, m, r, s, t, u, v, G, or V command.
       All  changes  made  to  the  buffer by a g, G, v, or V global command shall be undone as a
       single change; if no changes were made by the global command (such as with g/RE/ p), the u
       command  shall  have  no  effect. The current line number shall be set to the value it had
       immediately before the command being undone started.

   Global Non-Matched Command
       Synopsis:

              (1,$)v/RE/command list

       This command shall be equivalent to the global command g except that the  lines  that  are
       marked  during  the first step shall be those for which the line excluding the terminating
       <newline> does not match the RE.

   Interactive Global Not-Matched Command
       Synopsis:

              (1,$)V/RE/

       This command shall be equivalent to the interactive global command G except that the lines
       that  are  marked  during  the  first step shall be those for which the line excluding the
       terminating <newline> does not match the RE.

   Write Command
       Synopsis:

              (1,$)w [file]

       The w command shall write the addressed lines into the file named by  the  pathname  file.
       The  command shall create the file, if it does not exist, or shall replace the contents of
       the existing file. The currently remembered pathname shall not be changed unless there  is
       no  remembered  pathname.  If  no pathname is given, the currently remembered pathname, if
       any, shall be used (see the e and f commands); the current line number shall be unchanged.
       If  the  command  is  successful, the number of bytes written shall be written to standard
       output, unless the -s option was specified, in the following format:

              "%d\n", <number of bytes written>

       If file begins with '!' , the rest of the line shall be taken to be a shell  command  line
       whose  standard input shall be the addressed lines. Such a shell command line shall not be
       remembered as the current pathname. This usage of the write command with '!' shall not  be
       considered  as  a  "last w command that wrote the entire buffer", as described previously;
       thus, this alone shall not prevent the warning to the  user  if  an  attempt  is  made  to
       destroy the editor buffer via the e or q commands.

   Line Number Command
       Synopsis:

              ($)=

       The line number of the addressed line shall be written to standard output in the following
       format:

              "%d\n", <line number>

       The current line number shall be unchanged by this command.

   Shell Escape Command
       Synopsis:

              !command

       The remainder of the line after the '!' shall be sent to the  command  interpreter  to  be
       interpreted  as  a  shell  command  line.  Within the text of that shell command line, the
       unescaped character '%' shall be replaced with the remembered pathname; if a  '!'  appears
       as  the first character of the command, it shall be replaced with the text of the previous
       shell command executed via '!' . Thus, "!!" shall repeat the  previous  !command.  If  any
       replacements  of  '%'  or  '!'  are  performed,  the modified line shall be written to the
       standard output before command is executed. The ! command shall write:

              "!\n"

       to standard output upon completion, unless the -s option is specified.  The  current  line
       number shall be unchanged.

   Null Command
       Synopsis:

              (.+1)

       An  address  alone  on  a  line shall cause the addressed line to be written.  A <newline>
       alone shall be equivalent to "+1p" . The current line number shall be set to  the  address
       of the written line.

EXIT STATUS

       The following exit values shall be returned:

        0     Successful completion without any file or command errors.

       >0     An error occurred.

CONSEQUENCES OF ERRORS

       When  an  error in the input script is encountered, or when an error is detected that is a
       consequence of the data (not) present in the file or due to an external condition such  as
       a read or write error:

        * If  the standard input is a terminal device file, all input shall be flushed, and a new
          command read.

        * If the standard input is a regular file,  ed  shall  terminate  with  a  non-zero  exit
          status.

       The following sections are informative.

APPLICATION USAGE

       Because  of  the  extremely terse nature of the default error messages, the prudent script
       writer begins the ed input commands with an H command, so that if any errors do  occur  at
       least some clue as to the cause is made available.

       In previous versions, an obsolescent - option was described.  This is no longer specified.
       Applications should use the -s option. Using - as a file operand now produces  unspecified
       results. This allows implementations to continue to support the former required behavior.

EXAMPLES

       None.

RATIONALE

       The  initial  description  of  this  utility  was adapted from the SVID.  It contains some
       features not found in Version 7 or BSD-derived systems. Some of  the  differences  between
       the POSIX and BSD ed utilities include, but need not be limited to:

        * The BSD - option does not suppress the '!' prompt after a ! command.

        * BSD  does  not  support  the special meanings of the '%' and '!'  characters within a !
          command.

        * BSD does not support the addresses ';' and ',' .

        * BSD allows the command/suffix pairs pp, ll, and so on, which are  unspecified  in  this
          volume of IEEE Std 1003.1-2001.

        * BSD does not support the '!' character part of the e, r, or w commands.

        * A  failed  g command in BSD sets the line number to the last line searched if there are
          no matches.

        * BSD does not default the command list to the p command.

        * BSD does not support the G, h, H, n, or V commands.

        * On BSD, if there is no inserted text, the insert command changes the  current  line  to
          the referenced line -1; that is, the line before the specified line.

        * On  BSD,  the  join command with only a single address changes the current line to that
          address.

        * BSD does not support the P command; moreover, in  BSD  it  is  synonymous  with  the  p
          command.

        * BSD does not support the undo of the commands j, m, r, s, or t.

        * The  Version  7  ed  command W, and the BSD ed commands W, wq, and z are not present in
          this volume of IEEE Std 1003.1-2001.

       The -s option was added to allow the functionality of the now  withdrawn  -  option  in  a
       manner compatible with the Utility Syntax Guidelines.

       In  early  proposals  there  was  a  limit,  {ED_FILE_MAX},  that described the historical
       limitations of some ed utilities in their handling of large files; some of these have  had
       problems with files larger than 100000 bytes. It was this limitation that prompted much of
       the desire to include a split command in this volume of IEEE Std 1003.1-2001.  Since  this
       limit  was  removed,  this  volume  of  IEEE Std 1003.1-2001 requires that implementations
       document the file size limits imposed  by  ed  in  the  conformance  document.  The  limit
       {ED_LINE_MAX}  was  also removed; therefore, the global limit {LINE_MAX} is used for input
       and output lines.

       The manner in which the l command writes non-printable characters was changed to avoid the
       historical  backspace-overstrike  method.  On  video  display terminals, the overstrike is
       ambiguous because most terminals simply replace overstruck characters, making the l format
       not  useful  for  its  intended  purpose of unambiguously understanding the content of the
       line. The historical backslash escapes were also ambiguous.  (The  string  "a\0011"  could
       represent a line containing those six characters or a line containing the three characters
       'a' , a byte with a binary value of 1, and a 1.) In the format required here, a  backslash
       appearing  in  the  line  is  written as "\\" so that the output is truly unambiguous. The
       method of marking the ends of lines was adopted from the ex editor and is required for any
       line ending in <space>s; the '$' is placed on all lines so that a real '$' at the end of a
       line cannot be misinterpreted.

       Systems with bytes too large to fit into three octal digits must  devise  other  means  of
       displaying non-printable characters.  Consideration was given to requiring that the number
       of octal digits be large enough to hold a byte, but this seemed to be  too  confusing  for
       applications  on the vast majority of systems where three digits are adequate. It would be
       theoretically possible for the application to use the getconf  utility  to  find  out  the
       CHAR_BIT  value  and deal with such an algorithm; however, there is really no portable way
       that an application can use the octal values of the bytes across various  coded  character
       sets, so the additional specification was not worthwhile.

       The  description  of how a NUL is written was removed. The NUL character cannot be in text
       files, and this volume of IEEE Std 1003.1-2001 should not dictate behavior in the case  of
       undefined, erroneous input.

       Unlike  some  of the other editing utilities, the filenames accepted by the E, e, R, and r
       commands are not patterns.

       Early proposals stated that the -p option worked only when standard input  was  associated
       with  a  terminal  device. This has been changed to conform to historical implementations,
       thereby allowing applications to interpose themselves between a user and the ed utility.

       The form of the substitute command that uses the n suffix was limited in  some  historical
       documentation  (where this was described incorrectly as "backreferencing"). This limit has
       been omitted because there is no reason why  an  editor  processing  lines  of  {LINE_MAX}
       length  should  have this restriction. The command s/x/X/2047 should be able to substitute
       the 2047th occurrence of 'x' on a line.

       The use of printing commands with printing suffixes (such as pn, lp, and so on)  was  made
       unspecified because BSD-based systems allow this, whereas System V does not.

       Some BSD-based systems exit immediately upon receipt of end-of-file if all of the lines in
       the file have been deleted. Since this volume of  IEEE Std 1003.1-2001  refers  to  the  q
       command in this instance, such behavior is not allowed.

       Some  historical  implementations  returned  exit  status  zero even if command errors had
       occurred; this is not allowed by this volume of IEEE Std 1003.1-2001.

       Some historical implementations contained a bug that allowed a single period to be entered
       in  input  mode as <backslash> <period> <newline>. This is not allowed by ed because there
       is no description of escaping any of the characters in input mode; backslashes are entered
       into  the buffer exactly as typed. The typical method of entering a single period has been
       to precede it with another character and then use the substitute command  to  delete  that
       character.

       It  is difficult under some modes of some versions of historical operating system terminal
       drivers  to  distinguish  between  an  end-of-file  condition  and  terminal   disconnect.
       IEEE Std 1003.1-2001  does  not  require  implementations  to  distinguish between the two
       situations, which permits historical implementations  of  the  ed  utility  on  historical
       platforms  to  conform.  Implementations are encouraged to distinguish between the two, if
       possible, and take appropriate action on terminal disconnect.

       Historically, ed accepted a zero address for the a and r commands in order to insert  text
       at  the  start of the edit buffer. When the buffer was empty the command .= returned zero.
       IEEE Std 1003.1-2001 requires conformance to historical practice.

       For consistency with the a and r commands and better  user  functionality,  the  i  and  c
       commands  must also accept an address of 0, in which case 0i is treated as 1i and likewise
       for the c command.

       All of the following are valid addresses:

       +++    Three lines after the current line.

       /pattern/-
              One line before the next occurrence of pattern.

       -2     Two lines before the current line.

       3 ---- 2
              Line one (note the intermediate negative address).

       1 2 3  Line six.

       Any number of addresses can  be  provided  to  commands  taking  addresses;  for  example,
       "1,2,3,4,5p"  prints  lines 4 and 5, because two is the greatest valid number of addresses
       accepted by the print command. This, in combination with the semicolon delimiter,  permits
       users  to  create commands based on ordered patterns in the file. For example, the command
       "3;/foo/;+2p" will display the first line after line 3 that contains the pattern foo, plus
       the  next  two  lines.  Note  that  the  address "3;" must still be evaluated before being
       discarded, because the search origin for the "/foo/" command depends on this.

       Historically, ed disallowed address chains, as discussed above, consisting solely of comma
       or  semicolon  separators;  for  example,  ",,,"  or  ";;;"  were considered an error. For
       consistency of address specification, this restriction is  removed.  The  following  table
       lists some of the address forms now possible:

                        Address  Addr1  Addr2  Status      Comment
                        7,       7      7      Historical
                        7,5,     5      5      Historical
                        7,5,9    5      9      Historical
                        7,9      7      9      Historical
                        7,+      7      8      Historical
                        ,        1      $      Historical
                        ,7       1      7      Extension
                        ,,       $      $      Extension
                        ,;       $      $      Extension
                        7;       7      7      Historical
                        7;5;     5      5      Historical
                        7;5;9    5      9      Historical
                        7;5,9    5      9      Historical
                        7;$;4    $      4      Historical  Valid, but erroneous.
                        7;9      7      9      Historical
                        7;+      7      8      Historical
                        ;        .      $      Historical
                        ;7       .      7      Extension
                        ;;       $      $      Extension
                        ;,       $      $      Extension

       Historically,  values  could  be  added  to  addresses by including them after one or more
       <blank>s; for example, "3 - 5p" wrote the seventh line of the file, and "/foo/ 5" was  the
       same  as  "5 /foo/" . However, only absolute values could be added; for example, "5 /foo/"
       was an error. IEEE Std 1003.1-2001 requires conformance to historical practice.

       Historically, ed accepted the '^' character as an address, in which case it was  identical
       to the hyphen character. IEEE Std 1003.1-2001 does not require or prohibit this behavior.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Utility Description Defaults , ex , sed , sh , vi

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .