How to get GNU's readlink -f behavior on OS X.

README.md

readlink.sh is a pure shell implementation that uses dirname, basename, readlink and pwd utils. Note that you cannot rename it to just readlink as then the script will call itself instead of the system utility.

realpath script simply calls Python's os.path.realpath. Python is provided in OS X and major Linux distributions. You can use instead of the system utility by making a symlink: ln -s realpath readlink.

Another way is to install coreutils package via Homebrew or MacPorts and use greadlink.

The code is taken from the following page on StackOverflow: http://goo.gl/Yw9OY

readlink.sh

#!/bin/sh

TARGET=$1

cd $(dirname "$TARGET")
TARGET=$(basename "$TARGET")

# Iterate down a (possible) chain of symlinks
while [ -L "$TARGET" ]
do
    TARGET=$(readlink "$TARGET")
    cd $(dirname "$TARGET")
    TARGET=$(basename "$TARGET")
done

# Compute the canonicalized name by finding the physical path 
# for the directory we're in and appending the target file.
DIR=`pwd -P`
RESULT="$DIR/$TARGET"

echo $RESULT

realpath

#!/usr/bin/env python
import os,sys
print os.path.realpath(sys.argv[1])

which python3
prints this:
/Library/Frameworks/Python.framework/Versions/3.7/bin/python3

@dasgoll: No, there is not: (macOS 10.13)

$ which realpath
$ realpath
-bash: realpath: command not found

As I commented on SO, this needs cd -P, otherwise it will break on paths like this/is/a/link/..

I use the following script to create symlinks for my precious GNU packages on MacOS.
It checks every executable in /bin & /usr/bin if there is GNU alternative for it, and if it is, creates symlink in /usr/local/bin.
Also, note the echo at line 23 (function process-executable, then statement). DO NOT remove it on the first (dry) run. Check what the script outputs. Only then you are allowed to remove it.

#!/usr/bin/env bash

# =============================
# P R E R E Q U I S I T E S
# 
# $ brew install coreutils
# $ brew install findutils
# =============================

function process-executable()
{
    local executable="${1:?"Missing required parameter 'executable'"}"
    local name
    local target
    local link_name
    
    name="$(basename "${executable}" 2> /dev/null)"
    target="$(which "g${name}")"
    link_name="/usr/local/bin/${name}"
    
    # ToDo: remove 'echo' here
    if [[ -x "${target}" ]] && [[ ! -x "${link_name}" ]]
    then echo ln -sv "${target}" "${link_name}"
    fi
}

function search()
{ gfind -P /bin /usr/bin -xtype f -executable -exec bash "$0" {} \; ; }

function error()
{
    echo "ERROR:" "$@" >&2
    exit 1
}

function main()
{
    set -eu
    local nargs="$#"
    
    if (( "${nargs}" == 0 ))
    then search
    elif (( "${nargs}" == 1 ))
    then process-executable "$@"
    else error "Too many arguments!"
    fi
}

if [[ "${BASH_SOURCE[0]}" == "${0}" ]]
then main "$@"
fi