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Creating a Better cd Command in bash
Bash

Creating a Better cd Command in bash

InfinityCoder June 25, 2017

You cd into a lot of deep directories and would like to type cd ….. instead of cd ../ ../../.. to move up four levels.

Use this function:

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# cookbook filename: func_cd
 
# Allow use of 'cd ...' to cd up 2 levels, 'cd ....' up 3, etc. (like 4NT/4DOS)
# Usage: cd ..., etc.
function cd {
 
  local option= length= count= cdpath= i= # Local scope and start clean
 
  # If we have a -L or -P sym link option, save then remove it
  if [ "$1" = "-P" -o "$1" = "-L" ]; then
     option="$1"
     shift
  fi
 
  # Are we using the special syntax? Make sure $1 isn't empty, then
  # match the first 3 characters of $1 to see if they are '...' then
  # make sure there isn't a slash by trying a substitution; if it fails,
  # there's no slash. Both of these string routines require Bash 2.0+
  if [ -n "$1" -a "${1:0:3}" = '...' -a "$1" = "${1%/*}" ]; then
     # We are using special syntax
     length=${#1} # Assume that $1 has nothing but dots and count them
     count=2      # 'cd ..' still means up one level, so ignore first two
 
     # While we haven't run out of dots, keep cd'ing up 1 level
     for ((i=$count;i<=$length;i++)); do
          cdpath="${cdpath}../" # Build the cd path
     done
 
      # Actually do the cd
      builtin cd $option "$cdpath"
   elif [ -n "$1" ]; then
 
       # We are NOT using special syntax; just plain old cd by itself
       builtin cd $option "$*"
   else
 
       # We are NOT using special syntax; plain old cd by itself to home dir
       builtin cd $option
   fi
} # end of cd

The cd command takes an optional -L or -P argument that respectively follow symbolic links or follow the physical directory structure.

Either way, we have to take them into account if we want to redefine how cd works. Then, we make sure $1 isn’t empty and match the first three characters of $1 to see if they are ‘…’.

We then make sure there isn’t a slash by trying a substitution; if it fails, there’s no slash. Both of these string routines require bash version 2.0+.

After that, we build the actual cd command using a portable for loop and finally use the builtin command to use the shell cd and not create an endless loop by recursively calling our cd function.

We also pass in the -L or -P argument if present.

BASH Shell commands cd ( commands for linux )

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