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

OPTIONS         top

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

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.1‐2008 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         top

       None.

SEE ALSO         top

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

       The Base Definitions volume of POSIX.1‐2008, 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, 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 .

IEEE/The Open Group                 2013                            TEST(1P)