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Shells
CS155 ShellDiversity
Diversity
- What is a shell?
- The shell is the program that sits between you and the computer.
It understands things like
| and >,
where the programs cat and date can be found, etc.
- However, there are several shells …
Diversity
- Why several shells? Competition.
- Unix is a marketplace, where different solutions compete
for popularity. There are dozens of shells, just like there are
many brands of beer.
- It’s evolution in action—the better shells prosper, whereas the
lesser ones die.
- If you don’t like that, use Microsoft Windows. You get the one
solution that the giant company knows is best for you.
Popular shells
The most popular shells:
- sh – the Bourne shell, named after Stephen Bourne
- bash – the Bourne-Again shell
- ksh – the Korn shell
- zsh - another Bourneish shell
- csh – the C-shell, because it has syntax like the C language
- tcsh – another version of csh
What shell are we using?
% echo $SHELL
/bin/bash
- The various shells have different ways of doing things, just as various
natural languages (French, Chinese, Arabic) have different ways
of saying “hello”.
- However, the examples in this class should work for
tcsh, bash, or zsh.
- I like
bash best.
- Our IT department used to create new logins with
tcsh.
They switched to bash in 2011 or 2012, so older accounts
have tcsh, newer accounts have bash.
Temporarily switching shells
- To temporarily switch to a different shell,
type in the name of the shell you want to use. It’s just another command.
When you’re done with it, type
exit. The new shell will terminate,
and you’ll be back talking to your old shell.
Permanently switching shells
- To switch your shell permanently, send a request to the
systems & network administration people at
sna@cs.colostate.edu.
- Don’t bug them by changing your shell too often.
