test - perform tests on files and text

Synopsis

test [EXPRESSION]
[ [EXPRESSION] ]

Description

Tests the expression given and sets the exit status to 0 if true, and 1 if false. An expression is made up of one or more operators and their arguments.

The first form (test) is preferred. For compatibility with other shells, the second form is available: a matching pair of square brackets ([ [EXPRESSION ] ]).

This test is mostly POSIX-compatible.

When using a variable as an argument for a test operator you should almost always enclose it in double-quotes. There are only two situations it is safe to omit the quote marks. The first is when the argument is a literal string with no whitespace or other characters special to the shell (e.g., semicolon). For example, test -b /my/file. The second is using a variable that expands to exactly one element including if that element is the empty string (e.g., set x ''). If the variable is not set, set but with no value, or set to more than one value you must enclose it in double-quotes. For example, test "$x" = "$y". Since it is always safe to enclose variables in double-quotes when used as test arguments that is the recommended practice.

Operators for files and directories

  • -b FILE returns true if FILE is a block device.
  • -c FILE returns true if FILE is a character device.
  • -d FILE returns true if FILE is a directory.
  • -e FILE returns true if FILE exists.
  • -f FILE returns true if FILE is a regular file.
  • -g FILE returns true if FILE has the set-group-ID bit set.
  • -G FILE returns true if FILE exists and has the same group ID as the current user.
  • -k FILE returns true if FILE has the sticky bit set. If the OS does not support the concept it returns false. See https://en.wikipedia.org/wiki/Sticky_bit.
  • -L FILE returns true if FILE is a symbolic link.
  • -O FILE returns true if FILE exists and is owned by the current user.
  • -p FILE returns true if FILE is a named pipe.
  • -r FILE returns true if FILE is marked as readable.
  • -s FILE returns true if the size of FILE is greater than zero.
  • -S FILE returns true if FILE is a socket.
  • -t FD returns true if the file descriptor FD is a terminal (TTY).
  • -u FILE returns true if FILE has the set-user-ID bit set.
  • -w FILE returns true if FILE is marked as writable; note that this does not check if the filesystem is read-only.
  • -x FILE returns true if FILE is marked as executable.

Operators for text strings

  • STRING1 = STRING2 returns true if the strings STRING1 and STRING2 are identical.
  • STRING1 != STRING2 returns true if the strings STRING1 and STRING2 are not identical.
  • -n STRING returns true if the length of STRING is non-zero.
  • -z STRING returns true if the length of STRING is zero.

Operators to compare and examine numbers

  • NUM1 -eq NUM2 returns true if NUM1 and NUM2 are numerically equal.
  • NUM1 -ne NUM2 returns true if NUM1 and NUM2 are not numerically equal.
  • NUM1 -gt NUM2 returns true if NUM1 is greater than NUM2.
  • NUM1 -ge NUM2 returns true if NUM1 is greater than or equal to NUM2.
  • NUM1 -lt NUM2 returns true if NUM1 is less than NUM2.
  • NUM1 -le NUM2 returns true if NUM1 is less than or equal to NUM2.

Both integers and floating point numbers are supported.

Operators to combine expressions

  • COND1 -a COND2 returns true if both COND1 and COND2 are true.
  • COND1 -o COND2 returns true if either COND1 or COND2 are true.

Expressions can be inverted using the ! operator:

  • ! EXPRESSION returns true if EXPRESSION is false, and false if EXPRESSION is true.

Expressions can be grouped using parentheses.

  • ( EXPRESSION ) returns the value of EXPRESSION.
Note that parentheses will usually require escaping with \( to avoid being interpreted as a command substitution.

Examples

If the /tmp directory exists, copy the /etc/motd file to it:

if test -d /tmp
    cp /etc/motd /tmp/motd
end

If the variable MANPATH is defined and not empty, print the contents. (If MANPATH is not defined, then it will expand to zero arguments, unless quoted.)

if test -n "$MANPATH"
    echo $MANPATH
end

Parentheses and the -o and -a operators can be combined to produce more complicated expressions. In this example, success is printed if there is a /foo or /bar file as well as a /baz or /bat file.

if test \( -f /foo -o -f /bar \) -a \( -f /baz -o -f /bat \)
    echo Success.
end.

Numerical comparisons will simply fail if one of the operands is not a number:

if test 42 -eq "The answer to life, the universe and everything"
    echo So long and thanks for all the fish # will not be executed
end

A common comparison is with $status:

if test $status -eq 0
    echo "Previous command succeeded"
end

The previous test can likewise be inverted:

if test ! $status -eq 0
    echo "Previous command failed"
end

which is logically equivalent to the following:

if test $status -ne 0
    echo "Previous command failed"
end

Standards

test implements a subset of the IEEE Std 1003.1-2008 (POSIX.1) standard. The following exceptions apply:

  • The < and > operators for comparing strings are not implemented.
  • Because this test is a shell builtin and not a standalone utility, using the -c flag on a special file descriptors like standard input and output may not return the same result when invoked from within a pipe as one would expect when invoking the test utility in another shell.
In cases such as this, one can use command test to explicitly use the system's standalone test rather than this builtin test.