TEST(1)                    POSIX Programmer's Manual                   TEST(1)



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

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, where the utility name used is _[
       rather than test, the application shall ensure that the closing square
       bracket is a separate argument. The test and _[ utilities may be
       implemented as a single linked utility which examines the basename of
       the zeroth command line argument to determine whether to behave as the
       test or _[ variant. Applications using the exec() family of functions to
       execute these utilities shall ensure that the argument passed in arg0
       or argv[0] is ''[['' when executing the _[ utility and has a basename of
       "test" when executing the test utility.

OPTIONS
       The test utility shall not recognize the ""----"" argument in the manner
       specified by Guideline 10 in the Base Definitions volume of
       POSIX.1-2017, 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 an 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__operand -primary__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.1-2017, 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"

       Note that none of the following examples are permitted by the syntax
       described:


           [-f file]
           [-f file ]
           [ -f file]
           [ -f file
           test -f file ]

       In the first two cases, if a utility named [-f exists, that utility
       would be invoked, and not test.  In the remaining cases, the brackets
       are mismatched, and the behavior is unspecified. However:


           test ! ]

       does have a defined meaning, and must exit with status 1. Similarly:


           test ]

       must exit with status 0.

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.1-2017 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.1-2017,
       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.1-2017, 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 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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 .



IEEE/The Open Group                  2017                              TEST(1)
