working with directories

(Written by Paul Cobbaut, https://github.com/paulcobbaut/, with contributions by: Alex M. Schapelle, https://github.com/zero-pytagoras/)

This module is a brief overview of the most common commands to work with directories: pwd, cd, ls, mkdir and rmdir. These commands are available on any Linux (or Unix) system.

This module also discusses absolute and relative paths and path completion in the bash shell.

pwd

The you are here sign can be displayed with the pwd command (Print Working Directory). Go ahead, try it: Open a command line interface (also called a terminal, console or xterm) and type pwd. The tool displays your current directory.

student@linux:~$ pwd
/home/paul

cd

You can change your current directory with the cd command (Change Directory).

student@linux$ cd /etc
student@linux$ pwd
/etc
student@linux$ cd /bin
student@linux$ pwd
/bin
student@linux$ cd /home/paul/
student@linux$ pwd
/home/paul

cd \~

The cd is also a shortcut to get back into your home directory. Just typing cd without a target directory, will put you in your home directory. Typing cd ~ has the same effect.

student@linux$ cd /etc
student@linux$ pwd
/etc
student@linux$ cd
student@linux$ pwd
/home/paul
student@linux$ cd ~
student@linux$ pwd
/home/paul

cd ..

To go to the parent directory (the one just above your current directory in the directory tree), type cd .. .

student@linux$ pwd
/usr/share/games
student@linux$ cd ..
student@linux$ pwd
/usr/share

To stay in the current directory, type cd . ;-) We will see useful use of the . character representing the current directory later.

cd -

Another useful shortcut with cd is to just type cd - to go to the previous directory.

student@linux$ pwd
/home/paul
student@linux$ cd /etc
student@linux$ pwd
/etc
student@linux$ cd -
/home/paul
student@linux$ cd -
/etc

absolute and relative paths

You should be aware of absolute and relative paths in the file tree. When you type a path starting with a slash (/), then the root of the file tree is assumed. If you don\'t start your path with a slash, then the current directory is the assumed starting point.

The screenshot below first shows the current directory /home/paul. From within this directory, you have to type cd /home instead of cd home to go to the /home directory.

student@linux$ pwd
/home/paul
student@linux$ cd home
bash: cd: home: No such file or directory
student@linux$ cd /home
student@linux$ pwd
/home

When inside /home, you have to type cd paul instead of cd /paul to enter the subdirectory paul of the current directory /home.

student@linux$ pwd
/home
student@linux$ cd /paul
bash: cd: /paul: No such file or directory
student@linux$ cd paul
student@linux$ pwd
/home/paul

In case your current directory is the root directory /, then both cd /home and cd home will get you in the /home directory.

student@linux$ pwd
/
student@linux$ cd home
student@linux$ pwd
/home
student@linux$ cd /
student@linux$ cd /home 
student@linux$ pwd
/home

This was the last screenshot with pwd statements. From now on, the current directory will often be displayed in the prompt. Later in this book we will explain how the shell variable $PS1 can be configured to show this.

path completion

The tab key can help you in typing a path without errors. Typing cd /et followed by the tab key will expand the command line to cd /etc/. When typing cd /Et followed by the tab key, nothing will happen because you typed the wrong path (upper case E).

You will need fewer key strokes when using the tab key, and you will be sure your typed path is correct!

ls

You can list the contents of a directory with ls.

student@linux:~$ ls
allfiles.txt  dmesg.txt  services   stuff  summer.txt
student@linux:~$

ls -a

A frequently used option with ls is -a to show all files. Showing all files means including the hidden files. When a file name on a Linux file system starts with a dot, it is considered a hidden file and it doesn\'t show up in regular file listings.

student@linux:~$ ls
allfiles.txt  dmesg.txt  services  stuff  summer.txt
student@linux:~$ ls -a
.   allfiles.txt   .bash_profile  dmesg.txt   .lesshst  stuff
..  .bash_history  .bashrc        services    .ssh      summer.txt 
student@linux:~$

ls -l

Many times you will be using options with ls to display the contents of the directory in different formats or to display different parts of the directory. Typing just ls gives you a list of files in the directory. Typing ls -l (that is a letter L, not the number 1) gives you a long listing.

student@linux:~$ ls -l
total 17296
-rw-r--r-- 1 paul paul 17584442 Sep 17 00:03 allfiles.txt
-rw-r--r-- 1 paul paul    96650 Sep 17 00:03 dmesg.txt
-rw-r--r-- 1 paul paul    19558 Sep 17 00:04 services
drwxr-xr-x 2 paul paul     4096 Sep 17 00:04 stuff
-rw-r--r-- 1 paul paul        0 Sep 17 00:04 summer.txt

ls -lh

Another frequently used ls option is -h. It shows the numbers (file sizes) in a more human readable format. Also shown below is some variation in the way you can give the options to ls. We will explain the details of the output later in this book.

Note that we use the letter L as an option in this screenshot, not the number 1.

student@linux:~$ ls -l -h
total 17M
-rw-r--r-- 1 paul paul  17M Sep 17 00:03 allfiles.txt
-rw-r--r-- 1 paul paul  95K Sep 17 00:03 dmesg.txt
-rw-r--r-- 1 paul paul  20K Sep 17 00:04 services
drwxr-xr-x 2 paul paul 4.0K Sep 17 00:04 stuff
-rw-r--r-- 1 paul paul    0 Sep 17 00:04 summer.txt
student@linux:~$ ls -lh
total 17M
-rw-r--r-- 1 paul paul  17M Sep 17 00:03 allfiles.txt
-rw-r--r-- 1 paul paul  95K Sep 17 00:03 dmesg.txt
-rw-r--r-- 1 paul paul  20K Sep 17 00:04 services
drwxr-xr-x 2 paul paul 4.0K Sep 17 00:04 stuff
-rw-r--r-- 1 paul paul    0 Sep 17 00:04 summer.txt
student@linux:~$ ls -hl
total 17M
-rw-r--r-- 1 paul paul  17M Sep 17 00:03 allfiles.txt
-rw-r--r-- 1 paul paul  95K Sep 17 00:03 dmesg.txt
-rw-r--r-- 1 paul paul  20K Sep 17 00:04 services
drwxr-xr-x 2 paul paul 4.0K Sep 17 00:04 stuff
-rw-r--r-- 1 paul paul    0 Sep 17 00:04 summer.txt
student@linux:~$ ls -h -l
total 17M
-rw-r--r-- 1 paul paul  17M Sep 17 00:03 allfiles.txt
-rw-r--r-- 1 paul paul  95K Sep 17 00:03 dmesg.txt
-rw-r--r-- 1 paul paul  20K Sep 17 00:04 services
drwxr-xr-x 2 paul paul 4.0K Sep 17 00:04 stuff
-rw-r--r-- 1 paul paul    0 Sep 17 00:04 summer.txt
student@linux:~$

mkdir

Walking around the Unix file tree is fun, but it is even more fun to create your own directories with mkdir. You have to give at least one parameter to mkdir, the name of the new directory to be created. Think before you type a leading / .

student@linux:~$ mkdir mydir
student@linux:~$ cd mydir
student@linux:~/mydir$ ls -al
total 8
drwxr-xr-x  2 paul paul 4096 Sep 17 00:07 .
drwxr-xr-x 48 paul paul 4096 Sep 17 00:07 ..
student@linux:~/mydir$ mkdir stuff
student@linux:~/mydir$ mkdir otherstuff
student@linux:~/mydir$ ls -l
total 8
drwxr-xr-x 2 paul paul 4096 Sep 17 00:08 otherstuff
drwxr-xr-x 2 paul paul 4096 Sep 17 00:08 stuff
student@linux:~/mydir$

mkdir -p

The following command will fail, because the parent directory of threedirsdeep does not exist.

student@linux:~$ mkdir mydir2/mysubdir2/threedirsdeep
mkdir: cannot create directory ‘mydir2/mysubdir2/threedirsdeep’: No such fi\
le or directory

When given the option -p, then mkdir will create parent directories as needed.

student@linux:~$ mkdir -p mydir2/mysubdir2/threedirsdeep
student@linux:~$ cd mydir2
student@linux:~/mydir2$ ls -l
total 4
drwxr-xr-x 3 paul paul 4096 Sep 17 00:11 mysubdir2
student@linux:~/mydir2$ cd mysubdir2
student@linux:~/mydir2/mysubdir2$ ls -l
total 4
drwxr-xr-x 2 paul paul 4096 Sep 17 00:11 threedirsdeep
student@linux:~/mydir2/mysubdir2$ cd threedirsdeep/
student@linux:~/mydir2/mysubdir2/threedirsdeep$ pwd
/home/paul/mydir2/mysubdir2/threedirsdeep

rmdir

When a directory is empty, you can use rmdir to remove the directory.

student@linux:~/mydir$ ls -l
total 8
drwxr-xr-x 2 paul paul 4096 Sep 17 00:08 otherstuff
drwxr-xr-x 2 paul paul 4096 Sep 17 00:08 stuff
student@linux:~/mydir$ rmdir otherstuff
student@linux:~/mydir$ cd ..
student@linux:~$ rmdir mydir
rmdir: failed to remove ‘mydir’: Directory not empty
student@linux:~$ rmdir mydir/stuff
student@linux:~$ rmdir mydir
student@linux:~$

rmdir -p

And similar to the mkdir -p option, you can also use rmdir to recursively remove directories.

student@linux:~$ mkdir -p test42/subdir
student@linux:~$ rmdir -p test42/subdir
student@linux:~$

practice: working with directories

1. Display your current directory.

2. Change to the /etc directory.

3. Now change to your home directory using only three key presses.

4. Change to the /boot/grub directory using only eleven key presses.

5. Go to the parent directory of the current directory.

6. Go to the root directory.

7. List the contents of the root directory.

8. List a long listing of the root directory.

9. Stay where you are, and list the contents of /etc.

10. Stay where you are, and list the contents of /bin and /sbin.

11. Stay where you are, and list the contents of \~.

12. List all the files (including hidden files) in your home directory.

13. List the files in /boot in a human readable format.

14. Create a directory testdir in your home directory.

15. Change to the /etc directory, stay here and create a directory newdir in your home directory.

16. Create in one command the directories \~/dir1/dir2/dir3 (dir3 is a subdirectory from dir2, and dir2 is a subdirectory from dir1 ).

17. Remove the directory testdir.

18. If time permits (or if you are waiting for other students to finish this practice), use and understand pushd and popd. Use the man page of bash to find information about these commands.

solution: working with directories