test(1)
NAME
test − condition evaluation command
SYNOPSIS
test expr
[ expr ]
DESCRIPTION
test evaluates the expression expr and, if its value is true, returns a zero (true) exit status; otherwise, a non-zero (false) exit status is returned. test also returns a non-zero exit status if there are no arguments. The following primitives are used to construct expr:
-r file true if file exists and is readable.
-w file true if file exists and is writable.
-x file true if file exists and is executable.
-f file true if file exists and is a regular file.
-d file true if file exists and is a directory.
-c file true if file exists and is a character special file.
-b file true if file exists and is a block special file.
-p file true if file exists and is a named pipe (fifo).
-u file true if file exists and its set-user- ID bit is set.
-g file true if file exists and its set-group- ID bit is set.
-k file true if file exists and its sticky bit is set.
-s file true if file exists and has a size greater than zero.
-H file true if file exists and is a hidden directory (see cdf(4)).
-h file true if file exists and is a symbolic link.
-t [fildes] true if the open file whose file descriptor number is fildes (1 by default) is associated with a terminal device.
-z s1 true if the length of string s1 is zero.
-n s1 true if the length of the string s1 is non-zero.
s1 = s2 true if strings s1 and s2 are identical.
s1 != s2 true if strings s1 and s2 are not identical.
s1 true if s1 is not the null string.
n1 -eq n2 true if the integers n1 and n2 are algebraically equal. Any of the comparisons -ne, -gt, -ge, -lt, and -le can be used in place of -eq.
These primaries can be combined with the following operators:
! unary negation operator.
-a binary AND operator.
-o binary OR operator (-a has higher precedence than -o).
( expr ) parentheses for grouping.
Note that all the operators and flags are separate arguments to test. Note also that parentheses are significant to the shell and therefore must be escaped.
test is interpreted directly by the shell, and therefore does not exist as a separate executable program.
EXTERNAL INFLUENCES
International Code Set Support
Single- and multi-byte character code sets are supported.
EXAMPLES
Exit if there are not two or three arguments:
if [ $# -l2 2 -o $# -gt 3 ]; then exit 1; fi
Create a new file containing the text string default if the file does not already exist:
[ ! -f thisfile ] && echo default > thisfile
Wait for myfile to become non-readable:
while test -r myfile
do
sleep 30
done
echo ’"myfile" is no longer readable’
WARNINGS
When the [ form of this command is used, the matching ] must be the final argument, and both must be separate arguments from the arguments they enclose (white space delimiters required.
Parentheses and other special shell metacharacters intended to be handled by test must be escaped or quoted when invoking test from a shell.
Script writers should be careful when dealing with user-supplied input that could be confused with primaries and operators. Unless the application writer can control all the sources of input to the script, invocations such as:
test "$1" -a "$2"
or
[ "$1" -o "$2" ]
should be written as:
test "$1" && test "$2"
or
[ "$1" ] || [ "$2" ]
to avoid problems if the user supplies values such as $1 set to ! and $2 set to the null string. However, note that -a has higher precedence than -o in test, while && and || have equal precedence in the shell.
Another way to avoid such problems when comparing strings is to insert some non-operator character at the beginning of both operands:
test "X$response" = "Xexpected string"
This approach does not work with numeric comparisons or the unary operators because it would affect the operand being checked.
AUTHOR
test was developed by the University of California, Berkeley and HP.
SEE ALSO
STANDARDS CONFORMANCE
test: SVID2, XPG2, XPG3, POSIX.2
[: SVID2, XPG2, XPG3, POSIX.2
Hewlett-Packard Company — HP-UX Release 9.0: August 1992