COMMAND LINE

CommandLineIntro: DirectoryStack

Moving Again

So far you have probably already used the cd command to change your current working directory and the pwd command to find out what your current working directory is. After you work with the command line for a while, you'll find yourself changing directories constantly. In order to make this easier, Bash provides a "directory stack" that you can use to quickly move around directories where you are doing some work. (We'll show some examples in a moment that help explain the idea of a "stack.") You have the following commands at your disposal:

Command	Action
dirs	Display directory stack, top level first (left); other commands do this after their main action. Not all command options are shown in this table.
pushd dir	Push dir to the top of the stack and change the current working directory to it
pushd	Swap the top two stack levels and cd to the new top-of-stack
pushd +N	Rotate the whole stack left through N steps and cd to the new top-of-stack
pushd -N	Rotate the whole stack right through N+1 steps and cd to the new top-of-stack
popd	Remove the top-of-stack dir and cd to the new top-of-stack

If you need to have more of a visual aid to understanding a "stack", the simplest way is to imagine the "stack" as a pile of papers on your desk, you "push" new pieces of paper onto the top of the "stack" and you "pop" the top most piece of paper off the "stack". Both methods work on the principle of LIFO (last in first out).

You can play around with these commands to understand how they work. For example the following table provides a list of commands, their effect on the current working directory and their effect on the stack.

Command	Current working directory after command	Stack after command
cd	~	~
pushd /	/	/ ~
pushd /usr/bin	/usr/bin	/usr/bin / ~
pushd +1	/	/ ~ /usr/bin
pushd +1	~	~ /usr/bin /
popd	/usr/bin	/usr/bin /
pushd +1	/	/ /usr/bin
popd	/usr/bin	/usr/bin