datamaskinen

Thomas Frössman's blog on programming, technology, tools, or something like that.

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

My Bash Prompt

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UPDATE: I have changed my prompt again, read my bash prompt revisited

Introduction

This is an short but detailed description of a bash prompt. I’m happy with it and haven’t changed it much for a long time. 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 USER@HOSTNAME CURRENT-DIRECTORY $

Time

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

Username

The name of the currently logged in user. A maximum of 3 characters are displayed.

Hostname

The system hostname. A maximum of 4 characters are displayed.

Current directory

The current working directory. The full path is shown until a 15 characters limit has been reached, then only the initial letter of each directory leading up the the last one is displayed.

Hostnames, SSH and SSH key indicators:

bash prompt screenshot 2

Format:

SSH-KEY-INDICATOR TIME USER@HOST SSH-INDICATOR CURRENT-DIRECTORY $

Key indicator

The SSH key indicator K is shown at the leftmost position of the prompt when the SSH key is detected as loaded by an SSH agent. The key to be identified is chosen by setting an environment variable named SSH_KEY_FINGERPRINT. This can be done just before the prompt code in ~/.bashrc

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if [ -n "$SSH_CLIENT" ]; then
  SSH_KEY_FINGERPRINT="00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00"
  export SSH_KEY_FINGERPRINT

Hostname (again)

As seen in the above picture, different host names are automatically given a color to distinguish systems from each other a little bit more.

SSH indicator

The ssh indicator just displays SSH in a high color contrast towards the middle of the prompt line so that it is clear that you probably are on a remote system. This is a saftey feature.

Git repository meta data

bash prompt screenshot 3

Whats going on here?

The git git section of the prompt will show you things like branch name, if there are unstaged or uncommitted changes, if there are mergeable changes fetched or if all commits are pushed.

These features are straight from git’s bash integration which probably are located in /etc/bash_completion.d/git

The actual prompt code

To use this prompt, paste the following into ~/.bashrc or source it from a script:

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# Show indication that a certain SSH key is loaded
function __prompt_ssh_agent {
    if [ ! "z" == "z${SSH_KEY_FINGERPRINT}"  ]; then
       keys=`ssh-add -l  2> /dev/null | cut -d ' ' -f 2`
       for k in ${keys}; do
            [ "z$k" == "z${SSH_KEY_FINGERPRINT}" ] && echo -n "K "
       done
    fi
}

# Show user name
function __prompt_username {
    echo -n "$(whoami | cut -c1-3)"
}

# Show host name
function __prompt_hostname {
  echo -n "\[\033[1;$((31 + $(hostname | cksum | cut -c1-3) % 6))m\]\$(hostname | cut -c1-4)"
}

# Show an message if under an SSH session
function __prompt_ssh {
    if [ -n "$SSH_CLIENT" ]; then
        echo -n 'SSH '
    fi
}

# Show GIT status in the prompt
# (This feature is provided by the ubuntu debian git package)
export GIT_PS1_SHOWDIRTYSTATE="yes"
export GIT_PS1_SHOWUPSTREAM="auto"
export GIT_PS1_SHOWUNTRACKEDFILES="yes"

function __prompt_git_branch {
    __git_ps1 "(%s)"
}


# 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
}

# Show a compact version of the current directory
function __prompt_pwd {
    echo -n $(__dir_chomp  "$(pwd)" 15)
}


# Prompt output function
function proml {
  # The colors that the prompt uses
  local        BLUE="\[\033[0;34m\]"
  local         RED="\[\033[0;31m\]"
  local   LIGHT_RED="\[\033[1;31m\]"
  local       GREEN="\[\033[0;32m\]"
  local LIGHT_GREEN="\[\033[1;32m\]"
  local       WHITE="\[\033[1;37m\]"
  local  LIGHT_GRAY="\[\033[0;37m\]"

  # Set title in xterm*
  case $TERM in
    xterm*)
    TITLEBAR='\[\033]0;\u@\h:\w\007\]'
    ;;
    *)
    TITLEBAR=""
    ;;
  esac
# And finally, set the prompt 
PS1="${TITLEBAR}\
$LIGHT_GREEN\
\$(__prompt_ssh_agent)\
$RED\
\$(date +%H%M) \
$LIGHT_RED\$(__prompt_username)\
$BLUE@\
$(__prompt_hostname)\
$WHITE \
\$(__prompt_ssh)\
$GREEN\$(__prompt_pwd)\
$RED\$(__prompt_git_branch)\
$GREEN\$ \
$LIGHT_GRAY"
PS2='> '
PS4='+ '
}

# Execute the prompt function
proml

Blogs on Software Development

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Since having subscribed to far too many software developing blogs over the years I today decided to wipe all those subscriptions.

A OPML file for feed readers is here

The blogs

Javascript References on the Web

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A collection of sites I usually use as reference when I do javascript development.

I might not always agree on everything here, particulary in the code style section but everything is well worth a read.

The links

Guides (for learning javascript)

Language reference

Code style

Link repositories