Classic Shell Scripting

Appendix C. Important Unix Commands

Modern Unix systems come with hundreds and hundreds of commands. Many of them are specialized, but many are also generally useful, both in everyday interactive use and in shell scripts. It's impossible to cover every program on every system in existence, nor would that be useful. (Although books like Unix in a Nutshell make a valiant effort to describe a large cross section of what's out there.)

It is possible, however, to identify certain valuable commands, the ones that a Unix user or programmer should come to understand first, before moving on to the rest of the programs out there. Not surprisingly, many of these are the older commands that have been around since the early days of Unix. This appendix is our recommended list of commands that you should go out and study in order to improve your skills as a Unix developer. For brevity, we have resorted to simple, sorted, tabular lists of commands.

Shells and Built-in Commands

First and foremost, it pays to understand the Bourne shell language, particularly as codified by POSIX. Both bash and ksh93 are POSIX-compliant, and several other shells are compatible syntactically with the Bourne shell:

bash	The GNU Project's Bourne-Again Shell.
ksh	The Korn shell, either an original or clone, depending upon the operating system.
pdksh	The Public Domain Korn shell.
sh	The original Bourne shell, particularly on commercial Unix systems.
zsh	The Z-shell.

Along similar lines, you should understand ...