how do you normalize a file path in bash?

// realpath.c: display the absolute path to a file or directory.
// Adam Liss, August, 2007
// This program is provided "as-is" to the public domain, without express or
// implied warranty, for any non-profit use, provided this notice is maintained.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>
#include <limits.h>

static char *s_pMyName;

void usage(void);

int main(int argc, char *argv[])
{
    char
        sPath[PATH_MAX];


    s_pMyName = strdup(basename(argv[0]));

    if (argc < 2)
        usage();

    printf("%sn", realpath(argv[1], sPath));
    return 0;
}

void usage(void)
{
    fprintf(stderr, "usage: %s PATHn", s_pMyName);
    exit(1);
}

$ dirname /foo/bar/baz
/foo/bar
$ basename /foo/bar/baz
baz
$ dirname $( dirname  /foo/bar/baz  ))
/foo
$ realpath ../foo
../foo: No such file or directory
$ realpath /tmp/../tmp/../tmp
/tmp

readlink -f  /path/here/..

readlink -m /path/there/../../

realpath -s /path/here/../../

normalDir=`cd "${dirToNormalize}";pwd`
echo ${normalDir}

MY_PATH=$(readlink -f "$0")

get_abs_path() {
     local PARENT_DIR=$(dirname "$1")
     cd "$PARENT_DIR"
     local ABS_PATH="$(pwd)"/"$(basename $1)"
     cd - >/dev/null
     echo $ABS_PATH
}

python -c "import os,sys; print os.path.realpath(sys.argv[1])" /foo/bar/..

test -x /usr/bin/readlink || readlink () {
        echo $(/bin/ls -l $1 | /bin/cut -d'>' -f 2)
    }


test -x /usr/bin/realpath || realpath () {
    local PATH=/bin:/usr/bin
    local inputpath=$1
    local changemade=1
    while [ $changemade -ne 0 ]
    do
        changemade=0
        local realpath=""
        local token=
        for token in ${inputpath//// }
        do
            case $token in
            ""|".") # noop
                ;;
            "..") # up one directory
                changemade=1
                realpath=$(dirname $realpath)
                ;;
            *)
                if [ -h $realpath/$token ]
                then
                    changemade=1
                    target=`readlink $realpath/$token`
                    if [ "${target:0:1}" = '/' ]
                    then
                        realpath=$target
                    else
                        realpath="$realpath/$target"
                    fi
                else
                    realpath="$realpath/$token"
                fi
                ;;
            esac
        done
        inputpath=$realpath
    done
    echo $realpath
}

mkdir -p /tmp/bar
(cd /tmp ; ln -s /tmp/bar foo; ln -s ../.././usr /tmp/bar/link2usr)
echo `realpath /tmp/foo`

pushd foo/bar/..
dir=`pwd`
popd