Fancy Bash Prompts

While most people never change their Bash prompt, some of us suffer from a mild form of insanity that drives us to configure every option as far as the system will let us. This article is an example of how far you can push what most people would consider a simple option and hopefully will start a discussion on other prompt customizations and tweaks.

NOTE: The Bash Prompt Howto can be found at:
http://www.tldp.org/HOWTO/Bash-Prompt-HOWTO/

This is the Bash prompt that I've been using to get a little more system status information on each line.

Save the script to a file and source it from your .bashrc.

#!/bin/bash
# Filename:      custom_prompt.sh
# Maintainer:    Dave Vehrs 
# Last Modified: 12 Jul 2005 13:29:40 by Dave Vehrs

# Current Format: USER@HOST [dynamic section] { CURRENT DIRECTORY }$ 
# USER:      (also sets the base color for the prompt)
#   Red       == Root(UID 0) Login shell (i.e. sudo bash)
#   Light Red == Root(UID 0) Login shell (i.e. su -l or direct login)
#   Yellow    == Root(UID 0) priviledges in non-login shell (i.e. su)
#   Brown     == SU to user other than root(UID 0)
#   Green     == Normal user
# @:
#   Light Red == http_proxy environmental variable undefined.
#   Green     == http_proxy environmental variable configured.
# HOST:
#   Red       == Insecure remote connection (unknown type)
#   Yellow    == Insecure remote connection (Telnet)
#   Brown     == Insecure remote connection (RSH)
#   Cyan      == Secure remote connection (i.e. SSH)
#   Green     == Local session
# DYNAMIC SECTION:  
#     (If count is zero for any of the following, it will not appear)
#   [scr:#] ==== Number of detached screen sessions
#     Yellow    == 1-2
#     Red       == 3+
#   [bg:#]  ==== Number of backgrounded but still running jobs
#     Yellow    == 1-10
#     Red       == 11+
#   [stp:#] ==== Number of stopped (backgrounded) jobs
#     Yellow    == 1-2
#     Red       == 3+
# CURRENT DIRECTORY:     (truncated to 1/4 screen width)
#   Red       == Current user does not have write priviledges
#   Green     == Current user does have write priviledges
# NOTE:
#   1.  Displays message on day change at midnight on the line above the
#       prompt (Day changed to...). 
#   2.  Command is added to the history file each time you hit enter so its
#       available to all shells.

# Configure Colors:
COLOR_WHITE='\033[1;37m'
COLOR_LIGHTGRAY='033[0;37m'
COLOR_GRAY='\033[1;30m'
COLOR_BLACK='\033[0;30m'
COLOR_RED='\033[0;31m'
COLOR_LIGHTRED='\033[1;31m'
COLOR_GREEN='\033[0;32m'
COLOR_LIGHTGREEN='\033[1;32m'
COLOR_BROWN='\033[0;33m'
COLOR_YELLOW='\033[1;33m'
COLOR_BLUE='\033[0;34m'
COLOR_LIGHTBLUE='\033[1;34m'
COLOR_PURPLE='\033[0;35m'
COLOR_PINK='\033[1;35m'
COLOR_CYAN='\033[0;36m'
COLOR_LIGHTCYAN='\033[1;36m'
COLOR_DEFAULT='\033[0m'

# Function to set prompt_command to.
function promptcmd () {
    history -a 
    local SSH_FLAG=0
    local TTY=$(tty | awk -F/dev/ '{print $2}')
    if [[ ${TTY} ]]; then 
        local SESS_SRC=$(who | grep "$TTY "  | awk '{print $6 }')
    fi
    
    # Titlebar
    case ${TERM} in 
        xterm*  )  
            local TITLEBAR='\[\033]0;\u@\h: { \w }  \007\]'
            ;;
        *       )  
            local TITLEBAR=''                               
            ;;
    esac
    PS1="${TITLEBAR}"
  
    # Test for day change.
    if [ -z $DAY ] ; then
        export DAY=$(date +%A)
    else
        local today=$(date +%A)
        if [ "${DAY}" != "${today}" ]; then
            PS1="${PS1}\n\[${COLOR_GREEN}\]Day changed to $(date '+%A, %d %B %Y').\n"
            export DAY=$today
       fi
    fi
   
    # User
    if [ ${UID} -eq 0 ] ; then
        if [ "${USER}" == "${LOGNAME}" ]; then
            if [[ ${SUDO_USER} ]]; then
                PS1="${PS1}\[${COLOR_RED}\]\u"
            else
                PS1="${PS1}\[${COLOR_LIGHTRED}\]\u"
            fi
        else                               
            PS1="${PS1}\[${COLOR_YELLOW}\]\u"
        fi
    else
        if [ ${USER} == ${LOGNAME} ]; then     
            PS1="${PS1}\[${COLOR_GREEN}\]\u"
        else                               
            PS1="${PS1}\[${COLOR_BROWN}\]\u"
        fi
    fi

    # HTTP Proxy var configured or not
    if [ -n "$http_proxy" ] ; then
        PS1="${PS1}\[${COLOR_GREEN}\]@"
    else                               
        PS1="${PS1}\[${COLOR_LIGHTRED}\]@"
    fi

    # Host

    if [[ ${SSH_CLIENT} ]] || [[ ${SSH2_CLIENT} ]]; then 
        SSH_FLAG=1
    fi
    if [ ${SSH_FLAG} -eq 1 ]; then 
       PS1="${PS1}\[${COLOR_CYAN}\]\h "
    elif [[ -n ${SESS_SRC} ]]; then 
        if [ "${SESS_SRC}" == "(:0.0)" ]; then 
        PS1="${PS1}\[${COLOR_GREEN}\]\h "
        else 
            local parent_process=`cat /proc/${PPID}/cmdline`
            if [[ "$parent_process" == "in.rlogind*" ]]; then
                PS1="${PS1}\[${COLOR_BROWN}\]\h "
            elif [[ "$parent_process" == "in.telnetd*" ]]; then 
                PS1="${PS1}\[${COLOR_YELLOW}\]\h "
            else
                PS1="${PS1}\[${COLOR_LIGHTRED}\]\h "
            fi
        fi
    elif [[ "${SESS_SRC}" == "" ]]; then
        PS1="${PS1}\[${COLOR_GREEN}\]\h "
    else                                 
        PS1="${PS1}\[${COLOR_RED}\]\h " 
    fi

    # Detached Screen Sessions
    local DTCHSCRN=$(screen -ls | grep -c Detach )
    if [ ${DTCHSCRN} -gt 2 ]; then
        PS1="${PS1}\[${COLOR_RED}\][scr:${DTCHSCRN}] "
    elif [ ${DTCHSCRN} -gt 0 ]; then
        PS1="${PS1}\[${COLOR_YELLOW}\][scr:${DTCHSCRN}] "
    fi
   
    # Backgrounded running jobs
    local BKGJBS=$(jobs -r | wc -l )
    if [ ${BKGJBS} -gt 2 ]; then
        PS1="${PS1}\[${COLOR_RED}\][bg:${BKGJBS}]"
    elif [ ${BKGJBS} -gt 0 ]; then
        PS1="${PS1}\[${COLOR_YELLOW}\][bg:${BKGJBS}] "
    fi
    
    # Stopped Jobs
    local STPJBS=$(jobs -s | wc -l )
    if [ ${STPJBS} -gt 2 ]; then
        PS1="${PS1}\[${COLOR_RED}\][stp:${STPJBS}]"
    elif [ ${STPJBS} -gt 0 ]; then
        PS1="${PS1}\[${COLOR_YELLOW}\][stp:${STPJBS}] "
    fi
    
    # Bracket {
    if [ ${UID} -eq 0 ]; then              
        if [ "${USER}" == "${LOGNAME}" ]; then 
            if [[ ${SUDO_USER} ]]; then
                PS1="${PS1}\[${COLOR_RED}\]"
            else
                PS1="${PS1}\[${COLOR_LIGHTRED}\]"
            fi
        else                               
            PS1="${PS1}\[${COLOR_YELLOW}\]"
        fi
    else                                 
        if [ "${USER}" == "${LOGNAME}" ]; then 
            PS1="${PS1}\[${COLOR_GREEN}\]"
        else                               
            PS1="${PS1}\[${COLOR_BROWN}\]"
        fi
    fi
    PS1="${PS1}{ "
    
    # Working directory
    if [ -w "${PWD}" ]; then 
        PS1="${PS1}\[${COLOR_GREEN}\]$(prompt_workingdir)"
    else                                 
        PS1="${PS1}\[${COLOR_RED}\]$(prompt_workingdir)"
    fi
    
    # Closing bracket } and $\#
    if [ ${UID} -eq 0 ]; then              
        if [ "${USER}" == "${LOGNAME}" ]; then 
            if [[ ${SUDO_USER} ]]; then
                PS1="${PS1}\[${COLOR_RED}\]"
            else
                PS1="${PS1}\[${COLOR_LIGHTRED}\]"
            fi
        else                               
            PS1="${PS1}\[${COLOR_YELLOW}\]"
        fi
    else                                 
        if [ "${USER}" == "${LOGNAME}" ]; then 
            PS1="${PS1}\[${COLOR_GREEN}\]"
        else                               
            PS1="${PS1}\[${COLOR_BROWN}\]"
        fi
    fi
    PS1="${PS1} }\$\[${COLOR_DEFAULT}\] "
}     

# Trim working dir to 1/4 the screen width
function prompt_workingdir () {
  local pwdmaxlen=$(($COLUMNS/4))
  local trunc_symbol="..."
  if [[ $PWD == $HOME* ]]; then
    newPWD="~${PWD#$HOME}" 
  else
    newPWD=${PWD}
  fi
  if [ ${#newPWD} -gt $pwdmaxlen ]; then
    local pwdoffset=$(( ${#newPWD} - $pwdmaxlen + 3 ))
    newPWD="${trunc_symbol}${newPWD:$pwdoffset:$pwdmaxlen}"
  fi
  echo $newPWD
}

# Determine what prompt to display:
# 1.  Display simple custom prompt for shell sessions started
#     by script.  
# 2.  Display "bland" prompt for shell sessions within emacs or 
#     xemacs.
# 3   Display promptcmd for all other cases.

function load_prompt () {
    # Get PIDs
    local parent_process=$(cat /proc/$PPID/cmdline | cut -d \. -f 1)
    local my_process=$(cat /proc/$$/cmdline | cut -d \. -f 1)

    if  [[ $parent_process == script* ]]; then
        PROMPT_COMMAND=""
        PS1="\t - \# - \u@\H { \w }\$ "
    elif [[ $parent_process == emacs* || $parent_process == xemacs* ]]; then
        PROMPT_COMMAND=""
        PS1="\u@\h { \w }\$ "
    else
        export DAY=$(date +%A)
        PROMPT_COMMAND=promptcmd
     fi 
    export PS1 PROMPT_COMMAND
}

load_prompt

How about you? What interesting snippits or tricks do you have in your prompt?