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

PROLOG
       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  Guide-
       line  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 can-
		 not 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 pri-
       mary_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, Interna-
		 tionalization 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 inter-
		 nationalization 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 consid-
       ered a string comparison, which shall cause a syntax error when the second -d  is  encoun-
       tered. 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  individ-
       ual  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  vol-
       ume  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 pro-
       posal 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  discrep-
       ancy  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)
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