Chapter 5: Text, editors and the shell environment

Exercise: Customise your shell

On servera, use variables and PATH to run your own command, create an alias, and make your settings survive a new login by adding them to Bash's startup files with vim.

Customise your shell

Use and export variables.
Run your own script through PATH.
Make an alias and environment settings permanent.

Start the exercise

On workstation, start the exercise. It restores student's start-up files on servera to the originals and removes ~/bin.

[student@workstation ~]$ lab start sa-environment

Later tasks assume that you are logged in to the server they name: ssh student@servera from workstation, then sudo -i for a root shell.

See exporting at work

On servera, set a variable, check that a child shell doesn't see it, export it, and check again.

[student@workstation ~]$ ssh student@servera
[student@servera ~]$ TEAM=platform
[student@servera ~]$ bash -c 'echo team: $TEAM'
team:
[student@servera ~]$ export TEAM
[student@servera ~]$ bash -c 'echo team: $TEAM'
team: platform

Run your own command through PATH

~/bin is already in your PATH. Create the directory, write a two-line script into it, make it executable, and run it by name from anywhere. chmod +x marks a file as executable; chapter 7 explains it.

[student@servera ~]$ mkdir ~/bin
[student@servera ~]$ vim ~/bin/up

Type these two lines in insert mode, then save with :wq:

#!/bin/bash
echo "$(hostname -s) has been up $(uptime -p | cut -d" " -f2-)"

[student@servera ~]$ chmod +x ~/bin/up
[student@servera ~]$ cd /tmp
[student@servera tmp]$ up
servera has been up 16 minutes
[student@servera tmp]$ cd

The first line tells the system which program runs the script. Chapter 15 is all about writing scripts.

Add an alias and history time stamps to ~/.bashrc

Open ~/.bashrc with vim, press G to jump to the end, o to open a new line, and add:

alias now='date +%T'
export HISTTIMEFORMAT="%F %T "

Save with :wq, then apply it to your current shell:

[student@servera ~]$ source ~/.bashrc
[student@servera ~]$ now
10:24:15
[student@servera ~]$ history 2
   41  2026-10-03 10:24:12 source ~/.bashrc
   42  2026-10-03 10:24:15 now

Set your editor for every login

EDITOR is an environment variable that programs read, so it belongs in ~/.bash_profile. Add this line at its end with vim:

export EDITOR=vim

Prove the settings survive a new login

Log out and back in, then check all three:

[student@servera ~]$ exit
[student@workstation ~]$ ssh student@servera
[student@servera ~]$ type now
now is aliased to `date +%T'
[student@servera ~]$ echo $EDITOR
vim
[student@servera ~]$ echo "$HISTTIMEFORMAT"
%F %T

A new login shell read ~/.bash_profile, which ran ~/.bashrc, exactly as the startup diagram showed.

Put servera back

Remove the lines you added (in vim, dd on each), or leave them: the next reset restores the original files.

[student@servera ~]$ exit

Grade and finish

Check your work with lab grade sa-environment, then put the exercise away with lab finish sa-environment.