.. include:: ../header.txt

.. _test:

:command:`test`
===========================

.. index:: test

:title:`Linux for Programmers and Users`, Sections 6.9.2 and 6.9.3

.. program:: test

:command:`test`

   Evaluate a boolean expression setting the :ref:`exit` to indicate a
   *true* or *false* result. This is used to express the logic of the
   :ref:`control` used for shell script programming.

   Note from the synopsis that there are two ways to invoke :command:`test`
   -- either with the command or the alternate form using square brackets.
   The square brackets have the advantage of giving a more familiar look,
   but one must be careful to **leave spaces between the brackets and the
   boolean expression**.

SYNOPSIS

    :command:`test` *expression*

    [ *expression* ]

.. list-table:: **String Comparisons**
   :widths: 30 70

   * - -n *string*
     - True if length of string is non-zero
   * - -z *string*
     - True if length of string is zero
   * - *string1* == *string2*
     - True if the strings are equal
   * - *string1* != *string2*
     - True if the strings are not equal

Much of shell script programming often relates to working with files and
directories, so the following boolean expressions are frequently used.

.. list-table:: **File Oriented Expressions**
   :widths: 25 75

   * - -a *file*
     - True if the file exists
   * - -b *file*
     - True if the file exists and is a block-oriented special file
   * - -c *file*
     - True if the file exists and is a character-oriented special file
   * - -d *file*
     - True if the file exists and is a directory
   * - -e *file*
     - True if the file exists
   * - -g *file*
     - True if the file exists and its "set group ID" bit is set
   * - -p *file*
     - True if the file exists and is a named pipe
   * - -r *file*
     - True if the file exists and is readable
   * - -s *file*
     - True if the file exists and has a size greater than zero
   * - -t *fd*
     - True if the file descriptor is open refers to the terminal
   * - -u *file*
     - True if the file exists and its "set user ID" bit is set
   * - -w *file*
     - True if the file exists and is writable
   * - -x *file*
     - True if the file exists and is executable
   * - -O *file*
     - True if the file exists and is owned the effective user ID of the user.
   * - -G *file* 
     - True if the file exists and is owned the effective group ID of the user.
   * - -L *file*
     - True if the file exists and is a symbolic link
   * - -N *file*
     - True if the file exists and has been modified since it was last read
   * - -S *file*
     - True if the file exists and is a named socket
   * - *file1* -nt *file2*
     - True if *file1* is newer than *file2*
   * - *file1* -ot *file2*
     - True if *file1* is older than *file2*
   * - *file1* -ef *file2*
     - True if *file1* and *file2* have the same device and inode numbers

.. seealso:: :ref:`numerictest`