Bash script absolute path with OS X

I am trying to obtain the absolute path to the currently running script on OS X.

I saw many replies going for readlink -f $0. However since OS X's readlink is the same as BSD's, it just doesn't work (it works with GNU's version).

Is there an out-of-the-box solution to this?

Solution 1:

These three simple steps are going to solve this and many other OS X issues:

1. Install Homebrew
2. brew install coreutils
3. grealpath .

(3) may be changed to just realpath, see (2) output

Solution 2:

There's a realpath() C function that'll do the job, but I'm not seeing anything available on the command-line. Here's a quick and dirty replacement:

#!/bin/bash

realpath() {
    [[ $1 = /* ]] && echo "$1" || echo "$PWD/${1#./}"
}

realpath "$0"

This prints the path verbatim if it begins with a /. If not it must be a relative path, so it prepends $PWD to the front. The #./ part strips off ./ from the front of $1.

Solution 3:

I found the answer a bit wanting for a few reasons:
in particular, they don't resolve multiple levels of symbolic links, and they are extremely "Bash-y".

While the original question does explicitly ask for a "Bash script", it also makes mention of Mac OS X's BSD-like, non-GNU readlink.

So here's an attempt at some reasonable portability (I've checked it with bash as 'sh' and dash), resolving an arbitrary number of symbolic links; and it should also work with whitespace in the path(s).

This answer was previously edited, re-adding the local bashism. The point of this answer is a portable, POSIX solution. I have edited it to address variable scoping by changing it to a subshell function, rather than an inline one. Please do not edit.

#!/bin/sh
realpath() (
  OURPWD=$PWD
  cd "$(dirname "$1")"
  LINK=$(readlink "$(basename "$1")")
  while [ "$LINK" ]; do
    cd "$(dirname "$LINK")"
    LINK=$(readlink "$(basename "$1")")
  done
  REALPATH="$PWD/$(basename "$1")"
  cd "$OURPWD"
  echo "$REALPATH"
)
realpath "$@"

Hope that can be of some use to someone.

Solution 4:

A more command-line-friendly variant of the Python solution:

python -c 'import os, sys; print(os.path.realpath(sys.argv[1]))' ./my/path