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My Bash Prompt Revisited

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I recently wrote an entry about my bash prompt that made me think about it so much so that I created a new one :D.

This is an short but detailed description of my current bash prompt. The main focus is to highlight important information and conserve display space by keeping the prompt line as short as possible without sacrificing too much information.

Basic prompt functions

bash prompt screenshot 1

Format:

TIME USERALIAS/USERNAME@HOSTALIAS/HOSTNAME CURRENT-DIRECTORY $/#

Time

If more than one terminal is open at one time it can be useful to see when or in which order commands have been executed. The time format is 4 digits (24 hour clock). To conserve space the usual colon infix (:) is omitted.

User alias or name

Either alias to the real user name, otherwise a maximum of 4 characters of the actual user name are displayed.

Host alias or name

Either an alias to the real host name, otherwise a maximum of 4 characters of the actual host name are displayed.

Current directory

The current working directory. The full path is shown until a 25 characters limit has been reached, then only the initial letter of each directory leading up the the last one are displayed.

Last part

$ for a normal user or # for root prompt. If the previous command exited with an error the normal user prompt is replaced with ¤%&! and the root prompt with !!! #.

Host group, SSH and SSH agent:

bash prompt screenshot 2

USER@HOST DIRECTORY SSH-AGENT-INDICATOR(@)SSH-INDICATOR(ssh) $/#

SSH and SSH Agent indicators

The SSH indicator ssh is shown after the current working directory when connected though ssh. If an ssh agent is running the ssh prompt is prefixed with an @.

Hostname (again)

As seen in the picture above, the host name alias has a red background. This is because the system is identified as a server.

Git/version controlled meta data

bash prompt screenshot 3

Whats going on here?

The git vcs section of the prompt will show you branch name and if there are unstaged or uncommitted changes.

Vcprompt is called if it’s installed to support git/mercurial/subversion, otherwise git’s default prompt functions are used.

The actual prompt code

To use this prompt, paste the following into ~/.bashrc :

somehere in .bashrc…
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# ------------------------------------------------------------------------------
# Aliases for host and user names
#

# Provide user name alias for prompt
__user_alias() {
    case `whoami` in
        root)
            echo -n "###"
            ;;
        a00001)
            echo -n ".1"
            ;;
        *)
            echo -n ""
            ;;
    esac
}

# Provide host tags 
case `hostname -f` in
    *.ec2.internal)
        HOST_TAGS=":server:"
        ;;
    transwhale*|a00001*|kranky*|wonky*)
        HOST_TAGS=":workstation:"
        ;;
    *)
        HOST_TAGS=""
        ;;
esac
export HOST_TAGS

# Provide host alias names
case `hostname -f` in
    transwhale*)
        HOST_ALIAS="(^_^)"
        ;;

    ip-10-80-11-253.ec2.internal)
        HOST_ALIAS="tid"
        ;;
esac

[ -n "${HOST_ALIAS}" ] && export HOST_ALIAS


# ------------------------------------------------------------------------------
# Bash PROMPT
#


function __prompt_date {
    echo -n `date +%H%M`
}

# Username or alias
function __prompt_username {
    if [ "$(type -t __user_alias)" == "function" ]; then
        __user_alias
    else 
        echo -n "$(whoami | cut -c1-4)"
    fi
}

# Hostname or alias
function __prompt_hostname {
   if [[ -n ${HOST_ALIAS} ]]; then
       echo -n ${HOST_ALIAS}
   else
       echo -n "$(hostname | cut -c1-4)"
   fi
}

# SSH agent indicator
function __prompt_ssh_agent {
    if [ -n "${SSH_CLIENT}" ] && [ -n "${SSH_AUTH_SOCK}" ] && [ -e "${SSH_AUTH_SOCK}" ]; then
        echo -n "@"
    fi
}

# SSH session session indicator
function __prompt_ssh {
    if [ -n "$SSH_CLIENT" ]; then
        echo -n 'ssh'
    fi
}

# Show version controlled repository status.
# vcprompt is used if installed, otherwise __git_ps1 will be tried as well.
# Install vcsprompt -> hg clone https://bitbucket.org/mitsuhiko/vcprompt
export GIT_PS1_SHOWDIRTYSTATE="yes"
export GIT_PS1_SHOWUPSTREAM="no"
export GIT_PS1_SHOWUNTRACKEDFILES="yes"
function __prompt_vcs {
    if [[ $(which vcprompt) ]]; then
        vcprompt -f "(%n:%b%m%u)"
    elif [[ $(type -t __git_ps1) == "function" ]]; then
        __git_ps1 "(%s)"
    fi
}



# Support function to compactify a path
# copied: http://stackoverflow.com/questions/3497885/code-challenge-bash-prompt-path-shortener
function __dir_chomp {
    local p=${1/#$HOME/\~} b s
    # Remove [ and ] from strings
    # (also, regular expression matching on [ ] below creates infinite recursion.)
    p=${p//[/ }
    p=${p//]/ }
    # Remove multiple spaces, don't need them
    p=${p//  / }
    s=${#p}
    while [[ $p != ${p//\/} ]]&&(($s>$2))
    do
        p=${p#/}
        [[ $p =~ \.?. ]]
        b=$b/${BASH_REMATCH[0]}
        p=${p#*/}
        ((s=${#b}+${#p}))
    done
    echo ${b/\/~/\~}${b+/}$p
}

# Compact version of current working directory
function __prompt_pwd {
    echo -n $(__dir_chomp  "$(pwd)" 25)
}

# 
function __prompt_last {
  if [[ $EUID -eq 0 ]]; then
      if [[ ${RET} = "0" ]]; then
          echo -n "#"
      else
          echo -n '!!! #'
      fi
  else
      if [[ ${RET} = "0" ]]; then
          echo -n "\$"
      else
          echo -n '¤%&!'
      fi
  fi
}


PROMPT_COMMAND='export RET=$?;'

# Set up prompt
function __prompt_activate {

    local resetFormating="\[\033[0m\]"     # reset text format

    # regular colors
    local black="\[\033[0;30m\]"
    local red="\[\033[0;31m\]"
    local green="\[\033[0;32m\]"
    local yellow="\[\033[0;33m\]"
    local blue="\[\033[0;34m\]"
    local magenta="\[\033[0;35m\]"
    local cyan="\[\033[0;36m\]"
    local white="\[\033[0;37m\]"

    # High intensity colors
    local blackH="\[\033[0;90m\]"
    local redH="\[\033[0;91m\]"
    local greenH="\[\033[0;92m\]"
    local yellowH="\[\033[0;93m\]"
    local blueH="\[\033[0;94m\]"
    local magentaH="\[\033[0;95m\]"
    local cyanH="\[\033[0;96m\]"
    local whiteH="\[\033[0;97m\]"

    # background colors
    local blackB="\[\033[40m\]"
    local redB="\[\033[41m\]"
    local greenB="\[\033[42m\]"
    local yellowB="\[\033[43m\]"
    local blueB="\[\033[44m\]"
    local magentaB="\[\033[45m\]"
    local cyanB="\[\033[46m\]"
    local whiteB="\[\033[47m\]"

    # Select host name color based on HOST_TAGS environment variable
    case ${HOST_TAGS} in
        *:server:*)
            local HOST_COLOR=${black}${redB}
            ;;
        *:workstation:*)
            local HOST_COLOR=${blue}
            ;;
        *)
            local HOST_COLOR=${white}${blackB}
            ;;
    esac

    # Set title in xterm*
    case $TERM in
        xterm*|rxvt*)
            TITLEBAR='\[\033]0;\u@\h:\w\007\]'
            ;;
        *)
            TITLEBAR=""
            ;;
    esac

# Set the prompt 
PS1="${TITLEBAR}\
${red}\$(__prompt_date) \
${yellow}\$(__prompt_username)${redH}@${HOST_COLOR}\$(__prompt_hostname)\
${cyan}\$(__prompt_pwd)${green}\$(__prompt_vcs) \
${white}${magentaB}\$(__prompt_ssh_agent)${black}${magentaB}\$(__prompt_ssh)\
${magenta}\$(__prompt_last) \
${resetFormating}"
PS2='> '
PS4='+ '
}


# Activate the prompt code
__prompt_activate

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