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A few tips about the cd command

Author: Solène
Date: 04 September 2020
Tags: unix

NIL=> https://bsd.network/@solenepercent/104801174538540148 Comment on Mastodon

While everyone familiar with a shell know about the command `cd`

there are a few tips you should know.

Moving to your $HOME directory

$ pwd

/tmp

$ cd

$ pwd

/home/solene

Using `cd` without argument will change your current directory to

your $HOME.

Moving into someone $HOME directory

While this should fail most of the time because people shouldn't allow

anyone to visit their $HOME, there are use case it can be used though.

$ cd ~user1

$ pwd

/home/user1

$ cd ~solene

$ pwd

/home/solene

Using `~user` as a parameter will move to that user $HOME directory,

note that `cd` and `cd ~youruser` have the same result.

Moving to previous directory

This is a very useful command which allow going back and forth between

two directories.

$ pwd

/home/solene

$ cd /tmp

$ pwd

/tmp

$ cd -

/home/solene

$ pwd

/home/solene

When you use `cd -` the command will move to the previous directory

in which you were. There are two special variables in your shell:

`PWD` and `OLDPWD`, when you move somewhere, `OLDPWD` will hold

your current location before moving and then `PWD` hold the new

path. When you use `cd -` the two variables get exchanged, this

mean you can only jump from two paths using `cd -` multiple times.

Please note that when using `cd -` your new location is displayed.

Changing directory by modifying current PWD

thfr@ showed me a cd feature I never heard about, and it's the

perfect place to write about it. Note that this work in ksh and zsh

but is reported to not work in bash.

One example will explain better than any text.

$ pwd

/tmp/pobj/foobar-1.2.0/work

$ cd 1.2.0 2.4.0

/tmp/pobj/foobar-2.4.0/work

This tells `cd` to replace first parameter pattern by the second

parameter in the current `PWD` and then cd into it.

$ pwd

/home/solene

$ cd solene user1

/home/user1

This could be done in a bloated way with the following command:

$ cd $(echo $PWD | sed "s/solene/user1/")

I learned it a few minutes ago but I see a lot of uses cases where

I could use it.

Moving into the current directory after removal

In some specific case, like having your shell into a directory that

existed but was deleted and removed (this happens often when you

working into compilation directories).

A simple trick is to tell `cd` to go to the current location.

$ cd .

$ cd $PWD

And `cd` will go into the same path and you can start hacking

again in that directory.