Script Directory in Bash

Different ways for a Bash script to get the directory it's in. Some work better than others.

To set up the demo environment:

mkdir -p ~/tmp/dir_demo
cd ~/tmp
ln -s dir_demo/ alt_dir_demo
cd alt_dir_demo

# save the following script as dir_demo.sh

ln -s dir_demo.sh alt_demo.sh
. alt_demo.sh 

# $0 only works if this script is invoked directly as an executable,
# not sourced with `. dir_demo.sh`
echo "\$0='$0'"

# BASH_SOURCE is an array, but it only seems to have one element
echo "BASH_SOURCE='$BASH_SOURCE'"
echo "BASH_SOURCE[0]='${BASH_SOURCE[0]}'"

# Symlinked directories will be preserved
DIR_CD="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
echo "DIR_CD='$DIR_CD'"

# Resolves symlinks to canonical path
DIR_READLINK=$(dirname "`readlink -f "${BASH_SOURCE[0]}"`")
echo "DIR_READLINK='$DIR_READLINK'"

# Resolves script to canonical path and name
READLINK_PATH=`readlink -f "${BASH_SOURCE[0]}"`
echo "READLINK_PATH='$READLINK_PATH'"