Normalize paths with parent “..” directories in the middle in bash script

Question

I have a list of paths stored in a bash variable, such as the following

>>> MY_PATHS= ../Some/Path/ ../Some/Other/../Path/

I'd like to have a list of unique relative paths, but due to the ".." parent directory used in the second path I can't just pipe these to uniq .

Is there a standard linux way to normalize directory paths?

My desired result is this:

>>> echo $MY_UNIQUE_PATHS
../Some/Path/

Answer 1

It seems python's relpath can do it all for me...

#!/usr/bin/python
import sys, os, pipes
paths = sys.argv[1:]                 #arguments are a list of paths
paths = map(os.path.relpath, paths)  #"normalize" and convert to a relative path
paths = set(paths)                   #remove duplicates
paths = map(pipes.quote, paths)      #for filenames with spaces etc
print " ".join(paths)                #print result

Examples:

>>> normpath ../Some/Path/ ../Some/Other/../Path/
../Some/Path
>>> normpath ../Some/Path/ ../Some/Other/../Different\ Path/
'../Some/Different Path' ../Some/Path

If absolute paths are wanted, replace relpath with abspath .

Thanks, @devnull!

Answer 2

Here's a version just in bash, except for printing relative paths it still uses python's magical relpath function (see this ).

Note: Paths must exist otherwise realpath fails :(

#!/usr/bin/bash

IFS=$'\r\n' #so the arrays abspaths and relpaths are created with just newlines

#expand to absolute paths and remove duplicates
abspaths=($(for p in "$@"; do realpath "$p"; done | sort | uniq))
printf "%q " "${abspaths[@]}" #use printf to escape spaces etc
echo #newline after the above printf

#use python to get relative paths
relpath(){ python -c "import os.path; print os.path.relpath('$1','${2:-$PWD}')" ; } 
relpaths=($(for p in "${abspaths[@]}"; do relpath "$p"; done))
printf "%q " "${relpaths[@]}"
echo