.. _cmd-test: 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``.