Controlling the size of the $PWD in bash

Posted by mikhailian on Wed 12 Sep 2007 at 10:22

Debian shows the absolute path in the command prompt by default, and it can be really long, sometimes. This can take up valuable space in your shell windows.

To fix this, we can limit the command prompt to show only the last x characters using only the variable expansion features of bash 2.0.5+.

Just put the following snippet of code into ~/.bashrc

function truncate_pwd
{
 if [ $HOME == $PWD ]
 then
   newPWD="~"
 elif [ $HOME ==  ${PWD:0:${#HOME}} ]
 then
   newPWD="~${PWD:${#HOME}}"
 else
   newPWD=$PWD
 fi

  local pwdmaxlen=15
  if [ ${#newPWD} -gt $pwdmaxlen ]
  then
    local pwdoffset=$(( ${#newPWD} - $pwdmaxlen  ))
    newPWD=".+${newPWD:$pwdoffset:$pwdmaxlen}"
  fi
}

PROMPT_COMMAND=truncate_pwd
PS1="${ttyname}@\[${HOST_COLOUR}\]\h\[${RESET_COLOR}\]:\${newPWD}\\$ "

Since this code does not fork out sed, tr or wc, it is blazingly fast.

This article can be found online at the Debian Administration website at the following bookmarkable URL (along with associated comments):

http://www.debian-administration.org/article/Controlling_the_size_of_the_PWD_in_bash