Introduction to the Linux Command Line

The shell prompt is an often overlooked but highly customizable feature of the Linux terminal. Defined by the PS1 variable in bash, the prompt shows useful info like username, hostname, and current directory. By editing PS1, users can display dynamic elements, include colors, and even add a clock — blending both style and utility.

Prompt Anatomy

A typical bash prompt might look like:

[me@linuxbox ~]$

Defined by:

echo $PS1

[\u@\h \W]\$

It uses escape sequences interpreted by bash:

Sequence	Description
\a	ASCII bell (beep)
\d	Date (e.g., "Mon May 26")
\h	Hostname (short)
\u	Username
\w	Full path of current dir
\W	Base name of current dir
\t	Time (HH:MM:SS)
\@	Time (AM/PM format)
\!	Command history number
\$	Prompt character ($ or #)
\[	Start non-printing characters
\]	End non-printing characters

Experimenting with Prompt Designs

Back Up the Original

ps1_old="$PS1"

Minimal Prompt

PS1="\$ "

Add a Bell

PS1="

\[\a\]

\$ "

Informative Prompt (Time + Hostname)

PS1="\A \h \$ "

17:33 linuxbox $

Restore Original

PS1="$ps1_old"

Adding Color to the Prompt

Text Colors

Sequence	Color
\033[0;31m	Red
\033[1;32m	Light green
\033[0;33m	Brown
\033[1;34m	Light blue

Background Colors

Sequence	Color
\033[0;41m	Red background
\033[0;42m	Green background

Example: Red Text Prompt

PS1="

\[\033[0;31m\]

<\u@\h \W>\$

\[\033[0m\]

 "

Example: Red Background

PS1="

\[\033[0;41m\]

<\u@\h \W>\$

\[\033[0m\]

 "

Cursor Control

Escape Code	Action
\033[s	Save cursor position
\033[u	Restore cursor position
\033[0;0H	Move to top-left corner

Top Bar with Clock

PS1="

\[\033[s\033[0;0H\033[0;41m\033[K\033[1;33m\t\033[0m\033[u\]

<\u@\h \W>\$ "

Save Prompt Permanently

# Custom prompt with red bar and yellow clock

PS1="..."

export PS1

source ~/.bashrc

Conclusion

Customizing the shell prompt with PS1 lets users enhance both appearance and utility. With escape sequences for text, color, and cursor control, the terminal becomes more intuitive and personalized. Experimenting with these options improves the user experience and deepens command-line mastery.