Finds the real path of a possibly symlinked pathname.

canonical_path

#!/usr/bin/env bash
# Adapted from Maven's mvn script.
# Given a path possibly containing symlinks, work back to get the 
# real path. Useful when a script needs to derive its base dir from 
# $(dirname $0), but $0 is a symlink to the real script.

canonical_path() {
    local path="$1"
    while [ -L "$path" ]; do
        local link="$(expr "$(ls -ld "$path")" : '.*-> \(.*\)$')"
        if expr "$link" : '/.*' >/dev/null 2>&1; then
            path="$link" # absolute path in link
        else
            path="$(dirname "$path")/$link"
        fi
    done
    local dir
    dir="$(cd -P "$(dirname "$path")" >/dev/null 2>&1 && pwd)"
    if [ $? -ne 0 ]; then 
        echo $1 # fail - just echo the original and try to carry on
        return 1
    fi
    echo $dir/$(basename "$path")
}

# example usage:
BASEDIR="$(dirname $(canonical_path "$0"))"
# Now we have the real basedir, even if we were invoked as /usr/bin/foo etc.
if [ -f "$BASEDIR/foo.conf" ]; then ...