unix shell script find out which directory the script file resides?

#!/bin/bash

BASEDIR=$(dirname $0)
echo $BASEDIR

#!/bin/bash
# Absolute path to this script, e.g. /home/user/bin/foo.sh
SCRIPT=`readlink -f $0`
# Absolute path this script is in, thus /home/user/bin
SCRIPTPATH=`dirname $SCRIPT`
echo $SCRIPTPATH

#!/bin/tcsh
# Absolute path to this script, e.g. /home/user/bin/foo.csh
set SCRIPT=`readlink -f $0`
# Absolute path this script is in, thus /home/user/bin
set SCRIPTPATH=`dirname $SCRIPT`
echo $SCRIPTPATH

#!/bin/bash

current_dir=$(pwd)
script_dir=$(dirname $0)

echo $current_dir
echo $script_dir

/
/home/mez

#!/bin/bash

pushd $(dirname "${0}") > /dev/null
basedir=$(pwd -L)
# Use "pwd -P" for the path without links. man bash for more info.
popd > /dev/null

echo "${basedir}"

cd $(dirname $(readlink -f $0))

BASEDIR=$(dirname $0)
echo $BASEDIR

current_dir=$(pwd)
script_dir=$(dirname $0)

if [ $script_dir = '.' ]
then
script_dir="$current_dir"
fi

if [ -d "$Directory" -a -w "$Directory" ]
then
    #Statements
fi

"$_/../"