popd

Understanding popd

popd (pop directory) is a shell built-in command that removes the top directory from the directory stack and changes the current working directory to that directory. Essentially, it reverses the action of pushd. If you’ve used pushd to save a directory location, popd retrieves it and makes it your current directory. This avoids the need to manually type out lengthy or complex path names, speeding up your workflow.

Using popd in Action

Let’s look at popd through many code examples. Assume we start in our home directory (/home/user).

Example 1: Basic popd Usage

First, we’ll use pushd to save a directory:

pushd /tmp

This saves /tmp onto the directory stack. Now, let’s navigate to another directory:

cd /var/log

Now, using popd will bring us back to /tmp:

popd

Your current working directory should now be /tmp.

Example 2: popd with Multiple pushd commands

pushd maintains a stack of directories. Let’s see how popd handles multiple entries:

pushd /tmp
pushd /etc
pushd /usr/local
pwd  # Output: /usr/local
popd  # Returns to /etc
pwd  # Output: /etc
popd  # Returns to /tmp
pwd  # Output: /tmp
popd  # Returns to /home/user (or your home directory)
pwd  # Output: /home/user

As you can see, popd systematically pops directories off the stack in a Last-In, First-Out (LIFO) manner.

Example 3: popd and its -n option

The -n option prevents popd from changing the current directory. It only removes the top directory from the stack. This is useful when you want to manage the stack without altering your current location.

pushd /tmp
pushd /etc
popd -n
pwd  # Output: /etc (current directory remains unchanged)
dirs # Output: /tmp /home/user (shows the remaining directory stack)

Example 4: Error Handling

If the directory stack is empty, popd will generally report an error. The exact message will vary depending on your shell, but it will indicate that there are no directories to pop.

popd  # (Executed after all directories have been popped)

Example 5: Combining pushd, popd, and dirs

The dirs command is for inspecting the directory stack. Let’s use it alongside pushd and popd:

pushd /tmp
pushd /var/log
dirs # Output: /var/log /tmp /home/user
popd
dirs # Output: /tmp /home/user
popd
dirs # Output: /home/user

dirs shows you the current directory stack, providing context for your pushd and popd operations.

Using these examples as a foundation, you can incorporate popd effectively into your shell scripting and daily Linux workflow to efficiently manage your directory navigation. Experiment with these examples, modifying paths and using the -n option to gain a detailed understanding of this powerful command.