Working intimately with your Unix system requires spending a lot of time at the command shell, and, as such, you might want to customize your shell prompt to display information that's important to you. You can change the look and feel, and even add colors to your liking.

The  trick to controlling your shell prompt is using the PS1, PS2, PS3 and PS4 environment variables.

  • PS1: This parameter is expanded and used as the primary prompt string. The default value is s-v$ .
  • PS2: This parameter is expanded (as with PS1) and used as the secondary prompt string. The default is >
  • PS3: This parameter is used as the prompt for the select command
  • PS4: This parameter is expanded (as with PS1) and the value is printed before each command bash displays during an execution trace. The first character of PS4 is replicated multiple times, as necessary, to indicate multiple levels of indirection. The default is +

Let's take a look at some of this in action!

How Do I Modify My Prompt?

Let's take a look at the prompt as it is. On my machine, I'll run the following command:

[[email protected] ~]$ echo $PS1

and in return, I get some interesting output telling us how the prompt is constructed.

[[email protected] w]$

Here we can see how the current command line is constructed.

Let's say now, that I wanted to change my prompt to say something completely different. I would override my PS1 variable to do so:

export PS1="cow :"

and now I would get the following new prompt:

cow :

But that hardly seems useful. In order to properly customize your prompt, you can use any combination of special backslash-escaped sequences that are provided to you by the bash environment for your shell. They are as follows:

  • a : an ASCII bell character (07)
  • d : the date in "Weekday Month Date" format (e.g., "Tue May 26")
  • D{format} : the format is passed to strftime(3) and the result is inserted into the prompt string; an empty format results in a locale-specific time representation. The braces are required
  • e : an ASCII escape character (033)
  • h : the hostname up to the first '.'
  • H : the hostname
  • j : the number of jobs currently managed by the shell
  • l : the basename of the shell’s terminal device name
  • : newline
  • : carriage return
  • s : the name of the shell, the basename of $0 (the portion following the final slash)
  • : the current time in 24-hour HH:MM:SS format
  • T : the current time in 12-hour HH:MM:SS format
  • @ : the current time in 12-hour am/pm format
  • A : the current time in 24-hour HH:MM format
  • u : the username of the current user
  • v : the version of bash (e.g., 2.00)
  • V : the release of bash, version + patch level (e.g., 2.00.0)
  • w : the current working directory, with $HOME abbreviated with a tilde
  • W : the basename of the current working directory, with $HOME abbreviated with a tilde
  • ! : the history number of this command
  • # : the command number of this command
  • $ : if the effective UID is 0, a #, otherwise a $
  • nn : the character corresponding to the octal number nnn
  • \ : a backslash
  • [ : begin a sequence of non-printing characters, which could be used to embed a terminal control sequence into the prompt
  • ] : end a sequence of non-printing characters

Similarly, you can also use standard ANSI escape sequences to color your prompts, just as you would color any other text.

And that's it! Just play around with the combinations a bit until you find a prompt that is informative and comfortable for you.