Posts Tagged ‘command line

20
May
13

Keeping History Using the cd Command

If you use shell scripting a lot from the command line, this will probably improve your experience of it. This is for users of linux/mac command line or of cygwin on windows. Anywhere you can use the bash cd command.

Firstly (if you didn’t know) cd remembers the last directory you went to. To access this use;

cd -

This will change to the previous directory you were in. If you want to supercharge this you can add the following to your .bashrc/.profile/… customization file.

# petar marinov, http:/geocities.com/h2428, this is public domain
cd_func ()
{
  local x2 the_new_dir adir index
  local -i cnt

  if [[ $1 ==  "--" ]]; then
    dirs -v
    return 0
  fi

  the_new_dir=$1
  [[ -z $1 ]] && the_new_dir=$HOME

  if [[ ${the_new_dir:0:1} == '-' ]]; then
    #
    # Extract dir N from dirs
    index=${the_new_dir:1}
    [[ -z $index ]] && index=1
    adir=$(dirs +$index)
    [[ -z $adir ]] && return 1
    the_new_dir=$adir
  fi

  #
  # '~' has to be substituted by ${HOME}
  [[ ${the_new_dir:0:1} == '~' ]] && the_new_dir="${HOME}${the_new_dir:1}"

  #
  # Now change to the new dir and add to the top of the stack
  pushd "${the_new_dir}" > /dev/null
  [[ $? -ne 0 ]] && return 1
  the_new_dir=$(pwd)

  #
  # Trim down everything beyond 11th entry
  popd -n +11 2>/dev/null 1>/dev/null

  #
  # Remove any other occurence of this dir, skipping the top of the stack
  for ((cnt=1; cnt <= 10; cnt++)); do
    x2=$(dirs +${cnt} 2>/dev/null)
    [[ $? -ne 0 ]] && return 0
    [[ ${x2:0:1} == '~' ]] && x2="${HOME}${x2:1}"
    if [[ "${x2}" == "${the_new_dir}" ]]; then
      popd -n +$cnt 2>/dev/null 1>/dev/null
      cnt=cnt-1
    fi
  done

  return 0
}

alias cd=cd_func

This means that you can keep a history of the past 10 directories which you have visited and change between them.

To access this list type

cd --

Which will print a list like.

0  /e/projects/dgc/or14126h_3
1  /e/projects/dgc/or14126h_3/orthotics.dev
2  /c/Users/dgc/Dropbox/Coding
3  /e/projects/dgc
4  /e/projects/dgc/or14126h_2
5  /e/devdisk/dcm/configs
6  /e/devdisk/dcm
7  /e/devdisk
8  /e

And then

cd -5

will take you to entry 5 in the list.

To be clear I did not write this, I found it in the default cygwin .bashrc. The author of this was Petar Marinov.

I have found this very helpful, particularly when using a new python module. This is the process;

  • I would be in my working area
  • download it from pypi
  • cd to my download area
  • untar it
  • cd into it
  • run python setup.py install
  • then want to go back but cd – would get me to my download area.

This function removes that minor inconvenience and I have found it very useful.

Thanks for reading.