Shorter directory text in Bash prompt

Rather helpfully, David Goodwin left a comment about how he shortens the space taken up by the directory section of his terminal’s PS1 prompt by using a Bash script to remove the middle portion.

This is a really good idea, so I ported it into my PS1 set up which resulted in some rearranging and thought I’d share here as I modified for OS X and I don’t want to lose it!

The relevant portion of my .profile is:

# Git information for prompt
if [ -f $(brew --prefix)/etc/bash_completion.d/git-prompt.sh ]; then
    . $(brew --prefix)/etc/bash_completion.d/git-prompt.sh
fi
GIT_PS1_SHOWDIRTYSTATE=true
GIT_PS1_SHOWUNTRACKEDFILES=true

# Shorten current directory - Based on function by David Goodwin
function shorten_pwd()
{
    LENGTH="40"
    PART1="10"
    PART2="27"

    DIR=`echo "${PWD}" | sed "s/\\/home\\/$USER/~/" | sed "s/\\/Users\\/$USER/~/"`

    if [ ${#DIR} -gt $(($LENGTH)) ]; then
        echo "${DIR:0:$(($PART1))}...${DIR:$((${#DIR}-$PART2)):$PART2}"
    else
        echo "$DIR"
    fi
}


# Set prompt
prompt_cmd () {
    LAST_STATUS=$?

    local COLOUR_RESET='\[\e[0m\]'
    local BLACK='\[\e[0;30m\]'
    local RED='\[\e[0;31m\]'
    local GREEN='\[\e[0;32m\]'
    local YELLOW='\[\e[0;33m\]'
    local BLUE='\[\e[0;34m\]'
    local PURPLE='\[\e[0;35m\]'
    local CYAN='\[\e[0;36m\]'
    local WHITE='\[\e[0;37m\]'
    local BOLD_BLACK='\[\e[1;30m\]'
    local BOLD_RED='\[\e[1;31m\]'
    local BOLD_GREEN='\[\e[1;32m\]'
    local BOLD_YELLOW='\[\e[1;33m\]'
    local BOLD_BLUE='\[\e[1;34m\]'
    local BOLD_PURPLE='\[\e[1;35m\]'
    local BOLD_CYAN='\[\e[1;36m\]'
    local BOLD_WHITE='\[\e[1;37m\]'

    PS1="$BLACK\u@\h"     # user@host
    PS1+=" "
    PS1+="$BLUE"
    PS1+=$(shorten_pwd)   # current directory (usually \w)
    PS1+=" "
    PS1+="$RED"
    PS1+=$(__git_ps1)     # git status
    PS1+="$COLOUR_RESET"
    PS1+='\$ '
}

PROMPT_COMMAND='prompt_cmd && tab_title'

There are three sections here. Firstly we ensure that git-prompt.sh is loaded and configure a couple of settings for it. Then we write a function called shorten_cwd() based on David’s script. The main changes here are that I also look for /Users/$USER as that’s where OS X stores home directories and that I don’t split in the middle. Finally we define prompt_cmd() to set PS1 in a way that I understand and assign it to PROMPT_COMMAND along with tab_title.

The end result looks like this: