test(1p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

       test — evaluate expression

SYNOPSIS         top

       test [expression]

       [ [expression] ]

DESCRIPTION         top

       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         top

       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         top

       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         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       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         top

       Default.

STDOUT         top

       Not used.

STDERR         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       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         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       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         top

        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         top

       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         top

       None.

SEE ALSO         top

       Section 1.1.1.4, File Read, Write, and Creation, find(1p)

       The Base Definitions volume of POSIX.1‐2017, Chapter 8,
       Environment Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT         top

       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(1P)

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