Customize Shell and Eshell Prompt

My shell prompt was "localhost:~ Arreat$ blahblah" before. I've been bored with it for a long time. I decided to change it to simple style I like.

Shell

 I use bash. The variable which controls the prompt string is PS1(prompt string 1). So in my .bash_profile, I can add this:

export PS1="[\u@\h:\W, \@, \d]> "   #custom prompt options
whoami@hostname\current working directory\time\date

Here is a table of the options:

Description	csh*	ksh	bash	tcsh*	zsh
Current working directory	$CWD	$PWD	\w	%/	%/
Current working directory, with one's home directory by `~'	$CWD:t	$PWD##*/	\W	%~	%~
Full hostname	'uname -n'	'uname -n'	N/A	%M	%M
Hostname up to the first '.'	`hostname -s`	`hostname -s`	\h	%m	%m
Start (stop) boldfacing mode	%B (or %b)	N/A	N/A	%B (or %b)	%B (or %b)
Start (stop) standout mode	%S (or %s)	N/A	N/A	%S (or %s)	%S (or %s)
Start (stop) underline mode	%U (or %u)	N/A	N/A	%U (or %u)	%U (or %u)
User name	`whoami`	`logname`	\u	%n	%n
The shell's tty that the user is logged in on	%l	N/A	N/A	%|	%|
The current history number	%h	N/A	\!	%h (or %!)	%h (or %!)
Name of the shell	N/A	N/A	\s	N/A	N/A
Time of day in 12-hour hh:mm AM/PM	%t	N/A	\@	%t (or %@)	%t (or %@)
Time of day in 24-hour hh:mm	%T	N/A	\A	%T	%T
Time of day in 12-hour with seconds hh:mm:ss AM/PM	%p	N/A	\T	%p	N/A
Time of day in 24-hour with seconds hh:mm:nn	%P	N/A	\t	%P	%*
The day in 'dd' format	%D	N/A	N/A	%D	N/A
The month in 'Mon' format	%w	N/A	N/A	%w	N/A
The month in 'mm' format	%W	N/A	N/A	%W	N/A
The year in 'yy' format	%y	N/A	N/A	%y	N/A
The year in 'yyyy' format	%Y	N/A	N/A	%Y	N/A
The date in "Weekday Month Date" format	N/A	N/A	\d	N/A	N/A
The date in day-dd format	N/A	N/A	N/A	N/A	%w
The date in Mon/dd/yy format	N/A	N/A	N/A	N/A	%W
The date in yy-mm-dd format	N/A	N/A	N/A	N/A	%D
The weekday in 'Day' format	%d	N/A	N/A	%d	N/A
Description	csh*	ksh	bash	tcsh*	zsh

I mainly find stuffs about shell from the link below:
How to change your shell prompt You can find a lot of things about shell from this site.

Eshell 

As to eshll, I got information from EmacsWiki: Eshell Prompt

The Eshell prompt is generated by the function stored in ‘eshell-prompt-function’. When moving through the buffer, eshell also needs to know which lines start with a prompt. Therefore, whatever ‘eshell-prompt-function’ prints must be matched by ‘eshell-prompt-regexp’.

In my emacs init file, I add this:

(setq eshell-prompt-function
      (lambda ()
        (concat " $ "))) 

Though I don't know much about elisp, but I think it's quite clear what it means. And I also learned two command of emacs:

1.  C-h m: describe mode 
2.  C-h v: describe variable 

 Now my shell prompt is simple and clear, just my style :)