pushd

Berkely的学生写的

#!/bin/sh
# Chapter 14 - Functions
# This script implements the csh command pushd and pushes a
# directory onto the directory stack.
# You will need to "source" this file into your environment
# using the . command.

pushd() {

    # set the requested directory, $REQ, to the first argument
    # If no argument is given, set REQ to .

    REQ="$1"; 
    if [ -z "$REQ" ] ; then REQ=. ; fi

    # if $REQ is a directory, cd to the directory
    # if the cd is successful update $_DIR_STACK
    # otherwise issue the appropriate error messages

    if [ -d "$REQ" ] ; then
        cd "$REQ" > /dev/null 2>&1
        if [ $? -eq 0 ] ; then
            _DIR_STACK="`pwd`:$_DIR_STACK" ; export _DIR_STACK ;
            dirs
        else
            echo "ERROR: Cannot change to directory $REQ." >&2
        fi
    else
        echo "ERROR: $REQ is not a directory." >&2
    fi

    unset REQ

}