test(1)

NAME

test — condition evaluation command

SYNOPSIS

test expr

[ expr ]

DESCRIPTION

The test command evaluates the expression expr and, if its value is True, returns a zero (true) exit status; otherwise, a nonzero (false) exit status is returned. test also returns a nonzero 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 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. All file test operators return success if the argument is a symbolic link that points to a file of the file type being tested.

test is interpreted directly by the shell, and therefore does not exist as a separate executable program.

EXTERNAL INFLUENCES

International Code Set Support

Single byte and multibyte 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.

Avoid such problems when comparing strings by inserting a 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.

STANDARDS CONFORMANCE

test: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2

[: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2