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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 |
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TEST(1P) POSIX Programmer's Manual TEST(1P)
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.
test — evaluate expression
test [expression]
[ [expression] ]
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.
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.
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.
Not used.
None.
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.
Default.
Not used.
The standard error shall be used only for diagnostic messages.
None.
None.
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.
Default.
The following sections are informative.
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.
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
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.
None.
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
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)
Pages that refer to this page: find(1p), pathchk(1p), sh(1p), exec(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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