Fedora™ Unleashed, 2008 edition

Description	Location
ash	A small shell (sh-like)	/bin/ash
ash.static	A version of ash not dependent on software libraries	/bin/ash.static
bash	The Bourne Again SHell	/bin/bash
bsh	A symbolic link to ash	/bin/bsh
csh	The C shell, a symbolic link to tcsh	/bin/csh
ksh	The Korn shell	/bin/ksh, /usr/bin/ksh
pdksh	A symbolic link to ksh	/usr/bin/pdksh
rsh	The restricted shell (for network operation)	/usr/bin/rsh
sash	A standalone shell	/sbin/sash
sh	A symbolic link to bash	/bin/sh
tcsh	A csh-compatible shell	/bin/tcsh
zsh	A compatible csh, ksh, and sh shell	/bin/zsh

Learning More About Your Shell

All the shells listed in Table 11.1 have accompanying man pages, along with other documentation under the /usr/share/doc directory. Some of the documentation can be quite lengthy, but it is generally much better to have too much documentation than too little! The bash shell includes more than 100 pages in its manual, and the zsh shell documentation is so extensive that it includes the zshall meta man page (use man zshall to read this overview)!

The Shell Command Line

Having a basic understanding of the capabilities of the shell command line can help you write better shell scripts. If, after you have finished reading this short introduction, you want to learn more about the command line, check out Chapter 32, 'Command-Line Master Class.' You can use the shell command line to perform a number of different tasks, including

> Getting data from and sending data to a file or command, known as input and output redirection.

> Feeding or filtering a program's output to another command (called using pipes).

A shell can also have built-in job-control commands to launch the command line as a background process, suspend a running program, selectively retrieve or kill running or suspended programs, and perform other types of process control.

Multiple commands can be run on a single command line, with a semicolon to separate commands:

$ w ; free ; df
6:02pm up 4 days, 24 min, 1 user, load average: 0.00, 0.00, 0.00
USER  TTY   FROM             LOGIN@ IDLE  JCPU  PCPU  WHAT
bball pts/0 shuttle.home.org 1:14pm 0.00s 0.57s 0.01s w
       total         used    free shared buffers cached
Mem:  190684       184420    6264     76   17620 142820
-/+ buffers/cache:  23980  166704
Swap: 1277156        2516 1274640
Filesystem                  1k-blocks             Used Available Use% Mounted on