.. include:: ../header.txt

.. _access_var:

Accessing Variables
===========================

.. index:: accessing variables

:title:`Linux for Programmers and Users`, Section 6.3.2

+------------------+-------------------------------------------------------+
| Syntax           |       Action                                          |
+==================+=======================================================+
| $\ *name*        |   Returns the value of *name*.                        |
+------------------+-------------------------------------------------------+
| ${*name*}        | Use this form when the variable name is               |
|                  | followed by other characters, for example:            |
|                  | ``filename=${file}.txt``                              |
+------------------+-------------------------------------------------------+
| ${*name-word*}   | Returns *name* if set, and *word* otherwise.          |
+------------------+-------------------------------------------------------+
| ${*name=word*}   | Assigns *word* to *name* if *name* is not             |
|                  | already set. Returns *name*.                          |
+------------------+-------------------------------------------------------+
| ${#\ *name*}     | Returns the length of the value of *name*.            |
+------------------+-------------------------------------------------------+
| | ${*name#pat*}  | Removes the leading *pat* from *name*. The first      |
| | ${*name##pat*} | form removes the smallest matching pattern, the       |
|                  | second form removes the largest matching pattern.     |
+------------------+-------------------------------------------------------+
| | ${*name%pat*}  | Removes the trailing *pat* from *name*. The first     |
| | ${*name%%pat*} | form removes the smallest matching pattern, the       |
|                  | second form removes the largest matching pattern.     |
+------------------+-------------------------------------------------------+

Some Examples::

    $ file=foo
    $ echo ${file}.txt
    foo.txt
    $ b=bar
    $ echo ${file-$b}     --- already set
    foo
    $ echo ${bob-$b}      --- not set
    bar
    $ echo ${bob=wildcat} --- not set, assignment made
    wildcat
    $ echo ${bob=jayhawk} --- already set, assignment not made
    wildcat
    $ echo ${#bob}        --- string length
    7
    $ echo ${bob#wild}    --- remove first part
    cat
    $ echo ${bob%cat}     --- remove last part
    wild