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       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       test — evaluate expression

SYNOPSIS

       test [expression]

       [ [expression] ]

DESCRIPTION

       The  test  utility shall evaluate the expression and indicate the result of the evaluation
       by its exit status. An exit status of zero indicates that the expression evaluated as true
       and an exit status of 1 indicates that the expression evaluated as false.

       In the second form of the utility, which uses "[]" rather than test, the application shall
       ensure that the square brackets are separate arguments.

OPTIONS

       The test utility shall not  recognize  the  "−−"  argument  in  the  manner  specified  by
       Guideline  10 in the Base Definitions volume of POSIX.1‐2008, Section 12.2, Utility Syntax
       Guidelines.

       No options shall be supported.

OPERANDS

       The application shall ensure that all operators and elements of primaries are presented as
       separate arguments to the test utility.

       The following primaries can be used to construct expression:

       −b pathname
                 True  if  pathname  resolves  to en existing directory entry for a block special
                 file.  False if pathname cannot be resolved,  or  if  pathname  resolves  to  an
                 existing directory entry for a file that is not a block special file.

       −c pathname
                 True if pathname resolves to an existing directory entry for a character special
                 file.  False if pathname cannot be resolved,  or  if  pathname  resolves  to  an
                 existing directory entry for a file that is not a character special file.

       −d pathname
                 True  if pathname resolves to an existing directory entry for a directory. False
                 if pathname cannot be resolved, or if pathname resolves to an existing directory
                 entry for a file that is not a directory.

       −e pathname
                 True  if  pathname  resolves  to  an existing directory entry. False if pathname
                 cannot be resolved.

       −f pathname
                 True if pathname resolves to an existing directory entry  for  a  regular  file.
                 False  if  pathname  cannot  be resolved, or if pathname resolves to an existing
                 directory entry for a file that is not a regular file.

       −g pathname
                 True if pathname resolves to an existing directory entry for a file that has its
                 set-group-ID  flag  set.  False  if  pathname cannot be resolved, or if pathname
                 resolves to an existing directory entry for a file that does not have  its  set-
                 group-ID flag set.

       −h pathname
                 True  if  pathname  resolves to an existing directory entry for a symbolic link.
                 False if pathname cannot be resolved, or if pathname  resolves  to  an  existing
                 directory  entry  for a file that is not a symbolic link. If the final component
                 of pathname is a symbolic link, that symbolic link is not followed.

       −L pathname
                 True if pathname resolves to an existing directory entry for  a  symbolic  link.
                 False  if  pathname  cannot  be resolved, or if pathname resolves to an existing
                 directory entry for a file that is not a symbolic link. If the  final  component
                 of pathname is a symbolic link, that symbolic link is not followed.

       −n string True if the length of string is non-zero; otherwise, false.

       −p pathname
                 True  if  pathname  resolves to an existing directory entry for a FIFO. False if
                 pathname cannot be resolved, or if pathname resolves to  an  existing  directory
                 entry for a file that is not a FIFO.

       −r pathname
                 True  if  pathname  resolves to an existing directory entry for a file for which
                 permission to read from the file will be granted, as defined in Section 1.1.1.4,
                 File  Read,  Write,  and  Creation.  False if pathname cannot be resolved, or if
                 pathname resolves to an existing directory entry for a file for which permission
                 to read from the file will not be granted.

       −S pathname
                 True  if pathname resolves to an existing directory entry for a socket. False if
                 pathname cannot be resolved, or if pathname resolves to  an  existing  directory
                 entry for a file that is not a socket.

       −s pathname
                 True  if  pathname resolves to an existing directory entry for a file that has a
                 size greater than zero. False if pathname cannot be  resolved,  or  if  pathname
                 resolves  to  an  existing  directory entry for a file that does not have a size
                 greater than zero.

       −t file_descriptor
                 True if file descriptor number file_descriptor is open and is associated with  a
                 terminal.  False if file_descriptor is not a valid file descriptor number, or if
                 file descriptor number file_descriptor is not open, or if it is open but is  not
                 associated with a terminal.

       −u pathname
                 True if pathname resolves to an existing directory entry for a file that has its
                 set-user-ID flag set. False if pathname  cannot  be  resolved,  or  if  pathname
                 resolves  to  an existing directory entry for a file that does not have its set-
                 user-ID flag set.

       −w pathname
                 True if pathname resolves to an existing directory entry for a  file  for  which
                 permission  to write to the file will be granted, as defined in Section 1.1.1.4,
                 File Read, Write, and Creation.  False if pathname cannot  be  resolved,  or  if
                 pathname resolves to an existing directory entry for a file for which permission
                 to write to the file will not be granted.

       −x pathname
                 True if pathname resolves to an existing directory entry for a  file  for  which
                 permission  to  execute  the  file  (or search it, if it is a directory) will be
                 granted, as defined in Section 1.1.1.4, File Read, Write, and  Creation.   False
                 if pathname cannot be resolved, or if pathname resolves to an existing directory
                 entry for a file for which permission to execute (or search) the file  will  not
                 be granted.

       −z string True if the length of string string is zero; otherwise, false.

       string    True if the string string is not the null string; otherwise, false.

       s1 = s2   True if the strings s1 and s2 are identical; otherwise, false.

       s1 != s2  True if the strings s1 and s2 are not identical; otherwise, false.

       n1 −eq n2 True if the integers n1 and n2 are algebraically equal; otherwise, false.

       n1 −ne n2 True if the integers n1 and n2 are not algebraically equal; otherwise, false.

       n1 −gt n2 True  if the integer n1 is algebraically greater than the integer n2; otherwise,
                 false.

       n1 −ge n2 True if the integer n1 is algebraically greater than or equal to the integer n2;
                 otherwise, false.

       n1 −lt n2 True  if  the  integer  n1 is algebraically less than the integer n2; otherwise,
                 false.

       n1 −le n2 True if the integer n1 is algebraically less than or equal to  the  integer  n2;
                 otherwise, false.

       expression1 −a expression2
                 True  if  both  expression1  and  expression2 are true; otherwise, false. The −a
                 binary primary is left associative. It has a higher precedence than −o.

       expression1 −o expression2
                 True if either expression1 or expression2 is  true;  otherwise,  false.  The  −o
                 binary primary is left associative.

       With the exception of the −h pathname and −L pathname primaries, if a pathname argument is
       a symbolic link, test shall evaluate the expression by resolving  the  symbolic  link  and
       using the file referenced by the link.

       These primaries can be combined with the following operators:

       ! expression
                 True if expression is false. False if expression is true.

       ( expression )
                 True if expression is true. False if expression is false. The parentheses can be
                 used to alter the normal precedence and associativity.

       The primaries with two elements of the form:

           primary_operator primary_operand

       are known as unary primaries.  The primaries with three elements  in  either  of  the  two
       forms:

           primary_operandprimary_operator primary_operand

           primary_operand primary_operator primary_operand

       are   known   as   binary  primaries.   Additional  implementation-defined  operators  and
       primary_operators may be provided by implementations. They shall be of the form  −operator
       where the first character of operator is not a digit.

       The  algorithm  for  determining the precedence of the operators and the return value that
       shall be generated is based on the number of arguments presented to test.  (However,  when
       using  the "[...]" form, the <right-square-bracket> final argument shall not be counted in
       this algorithm.)

       In the following list, $1, $2, $3, and $4 represent the arguments presented to test:

       0 arguments:
                   Exit false (1).

       1 argument: Exit true (0) if $1 is not null; otherwise, exit false.

       2 arguments:
                    *  If $1 is '!', exit true if $2 is null, false if $2 is not null.

                    *  If $1 is a unary primary, exit true if the unary test is  true,  false  if
                       the unary test is false.

                    *  Otherwise, produce unspecified results.

       3 arguments:
                    *  If $2 is a binary primary, perform the binary test of $1 and $3.

                    *  If $1 is '!', negate the two-argument test of $2 and $3.

                    *  If $1 is '(' and $3 is ')', perform the unary test of $2.  On systems that
                       do not support the XSI option, the results are unspecified if  $1  is  '('
                       and $3 is ')'.

                    *  Otherwise, produce unspecified results.

       4 arguments:
                    *  If $1 is '!', negate the three-argument test of $2, $3, and $4.

                    *  If  $1  is  '(' and $4 is ')', perform the two-argument test of $2 and $3.
                       On systems that do not support the XSI option, the results are unspecified
                       if $1 is '(' and $4 is ')'.

                    *  Otherwise, the results are unspecified.

       >4 arguments:
                   The results are unspecified.

                   On  XSI-conformant  systems,  combinations of primaries and operators shall be
                   evaluated using the precedence and associativity rules  described  previously.
                   In  addition, the string comparison binary primaries '=' and "!=" shall have a
                   higher precedence than any unary primary.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of test:

       LANG      Provide a default value for the internationalization variables that are unset or
                 null.   (See   the   Base  Definitions  volume  of  POSIX.1‐2008,  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_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).

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

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

ASYNCHRONOUS EVENTS

       Default.

STDOUT

       Not used.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

       The following exit values shall be returned:

        0    expression evaluated to true.

        1    expression evaluated to false or expression was missing.

       >1    An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       The XSI extensions specifying the −a and −o binary primaries and the '(' and ')' operators
       have been marked obsolescent. (Many expressions using them are ambiguously defined by  the
       grammar  depending  on  the  specific  expressions  being  evaluated.) Scripts using these
       expressions should be converted to the forms given below. Even though many implementations
       will continue to support these obsolescent forms, scripts should be extremely careful when
       dealing with user-supplied input that could be confused with these and other primaries and
       operators.  Unless the application developer knows all the cases that produce input to the
       script, invocations like:

           test "$1" −a "$2"

       should be written as:

           test "$1" && test "$2"

       to avoid problems if a user supplied values such as $1 set to '!'  and $2 set to the  null
       string. That is, in cases where maximal portability is of concern, replace:

           test expr1 −a expr2

       with:

           test expr1 && test expr2

       and replace:

           test expr1 −o expr2

       with:

           test expr1 || test expr2

       but  note  that,  in test, −a has higher precedence than −o while "&&" and "||" have equal
       precedence in the shell.

       Parentheses or braces can be used in the shell command language to effect grouping.

       Parentheses must be escaped when using sh; for example:

           test \( expr1 −a expr2 \) −o expr3

       This command is not always portable  even  on  XSI-conformant  systems  depending  on  the
       expressions specified by expr1, expr2, and expr3.  The following form can be used instead:

           ( test expr1 && test expr2 ) || test expr3

       The two commands:

           test "$1"
           test ! "$1"

       could  not  be used reliably on some historical systems. Unexpected results would occur if
       such a string expression were used and $1 expanded to '!', '(', or a known unary  primary.
       Better constructs are:

           test −n "$1"
           test −z "$1"

       respectively.

       Historical systems have also been unreliable given the common construct:

           test "$response" = "expected string"

       One of the following is a more reliable form:

           test "X$response" = "Xexpected string"
           test "expected string" = "$response"

       Note  that  the  second  form  assumes that expected string could not be confused with any
       unary primary. If expected string starts with '−', '(', '!', or even '=', the  first  form
       should  be  used instead. Using the preceding rules without the XSI marked extensions, any
       of the three comparison forms is reliable,  given  any  input.  (However,  note  that  the
       strings are quoted in all cases.)

       Because  the  string  comparison  binary primaries, '=' and "!=", have a higher precedence
       than any unary primary in the greater than 4 argument case, unexpected results  can  occur
       if arguments are not properly prepared. For example, in:

           test −d $1 −o −d $2

       If  $1  evaluates  to  a  possible  directory  name  of '=', the first three arguments are
       considered a string comparison, which shall cause a syntax error when  the  second  −d  is
       encountered. One of the following forms prevents this; the second is preferred:

           test \( −d "$1" \) −o \( −d "$2" \)
           test −d "$1" || test −d "$2"

       Also in the greater than 4 argument case:

           test "$1" = "bat" −a "$2" = "ball"

       syntax  errors  occur  if $1 evaluates to '(' or '!'.  One of the following forms prevents
       this; the third is preferred:

           test "X$1" = "Xbat" −a "X$2" = "Xball"
           test "$1" = "bat" && test "$2" = "ball"
           test "X$1" = "Xbat" && test "X$2" = "Xball"

EXAMPLES

        1. Exit if there are not two or three arguments (two variations):

               if [ $# −ne 2 ] && [ $# −ne 3 ]; then exit 1; fi
               if [ $# −lt 2 ] || [ $# −gt 3 ]; then exit 1; fi

        2. Perform a mkdir if a directory does not exist:

               test ! −d tempdir && mkdir tempdir

        3. Wait for a file to become non-readable:

               while test −r thefile
               do
                   sleep 30
               done
               echo '"thefile" is no longer readable'

        4. Perform a command if the argument is one of three strings (two variations):

               if [ "$1" = "pear" ] || [ "$1" = "grape" ] || [ "$1" = "apple" ]
               then
                   command
               fi

               case "$1" in
                   pear|grape|apple) command ;;
               esac

RATIONALE

       The KornShell-derived conditional command (double bracket [[]]) was removed from the shell
       command  language  description  in an early proposal. Objections were raised that the real
       problem is misuse of the test command ([), and putting it into the shell is the wrong  way
       to  fix the problem.  Instead, proper documentation and a new shell reserved word (!)  are
       sufficient.

       Tests that require multiple  test  operations  can  be  done  at  the  shell  level  using
       individual  invocations  of  the  test  command  and shell logicals, rather than using the
       error-prone −o flag of test.

       XSI-conformant systems support more than four arguments.

       XSI-conformant systems support the combining of primaries with the following constructs:

       expression1 −a expression2
             True if both expression1 and expression2 are true.

       expression1 −o expression2
             True if at least one of expression1 and expression2 are true.

       ( expression )
             True if expression is true.

       In evaluating these more complex combined expressions, the following precedence rules  are
       used:

        *  The unary primaries have higher precedence than the algebraic binary primaries.

        *  The unary primaries have lower precedence than the string binary primaries.

        *  The unary and binary primaries have higher precedence than the unary string primary.

        *  The  !   operator  has higher precedence than the −a operator, and the −a operator has
           higher precedence than the −o operator.

        *  The −a and −o operators are left associative.

        *  The parentheses can be used to alter the normal precedence and associativity.

       The BSD and System V versions of −f are not the same. The BSD definition was:

       −f file   True if file exists and is not a directory.

       The SVID version (true if the file exists and is a  regular  file)  was  chosen  for  this
       volume  of POSIX.1‐2008 because its use is consistent with the −b, −c, −d, and −p operands
       (file exists and is a specific file type).

       The −e primary, possessing similar functionality to that provided  by  the  C  shell,  was
       added  because  it  provides  the only way for a shell script to find out if a file exists
       without trying to open the file. Since implementations are allowed to add additional  file
       types, a portable script cannot use:

           test −b foo −o −c foo −o −d foo −o −f foo −o −p foo

       to find out if foo is an existing file. On historical BSD systems, the existence of a file
       could be determined by:

           test −f foo −o −d foo

       but there was no easy way to determine that an existing file was a regular file. An  early
       proposal used the KornShell −a primary (with the same meaning), but this was changed to −e
       because there were concerns about the high probability of humans confusing the −a  primary
       with the −a binary operator.

       The  following options were not included in this volume of POSIX.1‐2008, although they are
       provided by some implementations. These operands should not be used by new implementations
       for other purposes:

       −k file   True if file exists and its sticky bit is set.

       −C file   True if file is a contiguous file.

       −V file   True if file is a version file.

       The following option was not included because it was undocumented in most implementations,
       has been removed from some implementations (including System V), and the functionality  is
       provided by the shell (see Section 2.6.2, Parameter Expansion.

       −l string The length of the string string.

       The −b, −c, −g, −p, −u, and −x operands are derived from the SVID; historical BSD does not
       provide them. The −k operand is derived from System V; historical BSD does not provide it.

       On historical BSD systems, test −w directory always returned false because test  tried  to
       open the directory for writing, which always fails.

       Some  additional  primaries  newly  invented  or  from  the KornShell appeared in an early
       proposal as part of the conditional command ([[]]): s1 > s2, s1 < s2, str =  pattern,  str
       !=  pattern,  f1 −nt f2, f1 −ot f2, and f1 −ef f2.  They were not carried forward into the
       test utility when the conditional command was removed from the shell because they have not
       been included in the test utility built into historical implementations of the sh utility.

       The  −t  file_descriptor primary is shown with a mandatory argument because the grammar is
       ambiguous if it can be omitted. Historical implementations have allowed it to be  omitted,
       providing a default of 1.

       It is noted that '[' is not part of the portable filename character set; however, since it
       is required to be encoded by a single byte, and is part of the portable character set, the
       name of this utility forms a character string across all supported locales.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Section 1.1.1.4, File Read, Write, and Creation, find

       The  Base  Definitions  volume  of POSIX.1‐2008, Chapter 8, Environment Variables, Section
       12.2, Utility Syntax Guidelines

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1,  2013  Edition,  Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013  by  the
       Institute  of  Electrical  and  Electronics  Engineers,  Inc and The Open Group.  (This is
       POSIX.1-2008 with the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/online.html .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .