View source for Shells Available for CS Accounts (bash, tcsh, etc.)

In Linux (and other Unixes), the ''shell'' is the program that provides a command line for you to type in commands and programs to run.  We have a number of shells available on our systems.

For accounts created before August 2018, the default shell was ''tcsh''.  Since August 2018, the default shell has been ''bash''.

== Shells Available on CS Linux Clients ==

The following shells are available on the CS [[:Category:Linux Clients|Linux clients]]:

* bash
* tcsh
* zsh
* ksh
* csh
* fish - but see [[#Caveats About fish|the caveats about fish]] below

== How to Tell What Shell You're Using ==

At a command line, run the following command:

 echo $0

It will print the name of the shell you're currently using.  In some circumstances, it might print a dash before the shell name.  You can just ignore the dash.

== How to Change Your Shell ==

On a CS [[:Category:Linux Clients|Linux client]], run the following command:

 chsh

When prompted for a new shell, you must type the full path to the shell. 
*  For grad net accounts, put "<code>/bin/</code>" in front of the shell name.  (e.g. <code>/bin/bash</code>)
*  For ugrad net accounts, put "<code>/usr/local/bin/</code>" in front of the shell name.  (e.g. <code>/usr/local/bin/zsh</code>)
** It will take about fifteen minutes before all of our ugrad Linux clients see the change.  If you log in to any of them immediately afterwards (before they've had time to get the update), you'll probably still be using your old shell.

== Setting Shell Variables ==

There are a number of environment variables that affect how your shell operates, especially <code>$PATH</code>, which tells the shell where to look for programs.  The way to change shell variables differs between bourne family shells (e.g. bash) and c-shell family shells (e.g. tcsh).

Let's say we want to add the <code>~/bin</code> directory to the front of our <code>$PATH</code>. 

In bash, that would be:

 export PATH="~/bin:$PATH"

In tcsh, that would be:

 setenv PATH "~/bin:$PATH"

== Shell Aliases ==

The syntax for aliases is only slightly different between bash and tcsh.

Let's say you have a <code>~/courses/cs220/assignments</code> directory that you access a lot.  You can make a command to quickly go to that directory no matter where your are at the moment.  Let's say you want to call the command "<code>cs220</code>".

In bash, you'd do this:

 alias cs220='cd ~/courses/cs220/assignments/'

In tcsh, you'd do this:

 alias cs220 'cd ~/courses/cs220/assignments/'

(Notice that there is no <code>=</code> in the tcsh example.)

== Configuration Files ==

If you want to save aliases or shell configurations to use every time you log in, you need to put them in a shell configuration file.

bash will use one of two files, depending on how it was started. 

* If it was started directly after logging in to the system, bash will use <code>~/.bash_profile</code> . 

* Otherwise, bash will use <code>~/.bashrc</code> .  

We recommend putting the following line into <code>~/.bash_profile</code> and then using <code>~/.bashrc</code> for all of your configurations:

 source ~/.bashrc

tcsh will use <code>~/.tcshrc</code> .

== Caveats About fish ==

Although fish is available on our systems, it ''cannot'' be used as a login shell, and we cannot provide support for it.  If you have a problem with fish, you'll have to either fix it yourself or switch to bash or tcsh for us to help you.  (fish is not POSIX compatible, so our standard configuration files cannot be easily applied to it.)

Much of the bash/tcsh examples above will also not work with fish.

[https://wiki.archlinux.org/index.php/Fish The ArchWiki fish page] may serve as a useful resource for making use of fish, though we don't guarantee that anything there will definitely work on our systems.

[[Category:Misc]]