Bash Prompt stuff

The following is what Gentoo sets its bash prompt:

if [ `/usr/bin/whoami` = 'root' ]
then
        if [ "$SHELL" = '/bin/bash' ] || [ "$SHELL" = '/bin/sh' ]
        then
                export PS1='\[\033[01;31m\]\h \[\033[01;34m\]\W \$ \[\033[00m\]'
        fi
else
        if [ "$SHELL" = '/bin/bash' ] || [ "$SHELL" = '/bin/sh' ]
        then
                export PS1='\[\033[01;32m\]\u@\h \[\033[01;34m\]\W \$ \[\033[00m\]'
        fi
fi

One can read the manpage of bash to see what the \u, \h and \W means. Most of the things on the setting of PS1 is to turn on the color, for example, when you are root, the hostname shall be in red but a normal user should see it green. The number 01;32 is what means green and it is the ANSI code for controlling that. (I miss the time when everyone is using 16-color EGA display!).

We can even control the title of xterm using similar tricks, see the code snippet I put below:

export PS1='\[\e]2;\u@\h \W\a\e[32m\]\u@\h \[\e[34m\]\W \$ \[\e[0m\]'

##################################################
# ANSI codes
##################################################
# Begin of control characters   \[
# End of control characters     \]
# XTerm titlebar text           \e]2;<text>\a
# Reset color to the default    \e[0m
# Foreground + Background       \e[<fg>;<bg>m
# Foreground w/o background     \e[<fg>m
#       Background: Black       40
#       Background: Red         41
#       Background: Green       42
#       Background: Brown       43
#       Background: Blue        44
#       Background: Purple      45
#       Background: Cyan        46
#       Background: Grey        47
#       Foreground: Black       0;30    Grey    1;30
#       Foreground: Lt Red      0;31    Red     1;31
#       Foreground: Lt Green    0;32    Green   1;32
#       Foreground: Lt Brown    0;33    Yellow  1;33
#       Foreground: Lt Blue     0;34    Blue    1;34
#       Foreground: Lt Purple   0;35    Purple  1;35
#       Foreground: Lt Cyan     0;36    Cyan    1;36
#       Foreground: Lt Grey     0;37    White   1;37

One thing to note: All the ANSI code for controlling colors (i.e. non-printing stuff) must be escaped by a pair of \[ and \], otherwise your bash prompt will be broken when wrapping a very long command line.