An alias is a way to give a
command a different name for use in the shell. Aliases provide an
excellent way to improve efficiency and productivity when using shell
commands. When set from the command line, aliases are only activated
for the shell in which they are created. Adding aliases to your .kshrc
(covered in Chapter 15) file will activate them upon login or whenever a new window or shell
is opened.
| Command Format: |
| alias
aliasname=value |
Figure
summarizes the reasons to use aliases. Figure
shows some examples creating aliases. Use single quotes for commands
with options, spaces or other special characters. Note that there are
no spaces between the alias command, the equal sign (=), and the
command(s) being assigned to the alias.
- Substitute a short command for a
long one - You can reduce the number of keystrokes for
commonly used long commands by creating an alias for the command.
See Examples 1 and 2 in Figure

- Create a single command for a
series of commands - You can string several commands together
and assign them one short alias name to reduce keystrokes. See
Example 3 in Figure

- Create alternate forms of
existing commands - Some commands such as rm (remove
files and directories) and cp (copy files) can be
dangerous. If you are not careful, you could accidentally
overwrite an important file. An alias will allow you to change the
meaning of these commands to include the -i option so they prompt
a user before overwriting a file or directory. See Example 4 in
Figure

Displaying Aliases - To display
aliases, use the alias
command with no argument. Figure
shows using the alias
command to display all aliases set for the current session. Some
aliases are pre-defined as part of the Korn shell.
Removing an Alias in the Current Shell - You can unset a
previously defined alias with the unalias
command. Figure
shows using the unalias
command to unset the "bye" alias, which will no
longer appear in the alias listing. You can also temporarily bypass an
Alias.
To bypass the alias and use the original version of a command,
use a backslash.
| Command Format: |
unalias aliasname
|
|