About Bash projects

Unless stated, all your projects will be auto-corrected with Ubuntu 20.04 LTS.

Concepts

For this project, we expect you to look at this concept:

Struggling with the sandbox? Try this: Using Docker & WSL on your local host

Resources

Read or watch:

Permissions

man or help:

chmod
sudo
su
chown
chgrp
id
groups
whoami
adduser
useradd
addgroup

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, *without the help of Google:

Permissions

What do the commands chmod, sudo, su, chown, chgrp do
Linux file permissions
How to represent each of the three sets of permissions (owner, group, and other) as a single digit
How to change permissions, owner and group of a file
Why can’t a normal user chown a file
How to run a command with root privileges
How to change user ID or become superuser

Other Man Pages

How to create a user
How to create a group
How to print real and effective user and group IDs
How to print the groups a user is in
How to print the effective userid

Requirements

General

Allowed editors: vi, vim, emacs
All your scripts will be tested on Ubuntu 20.04 LTS
All your scripts should be exactly two lines long ($ wc -l file should print 2)
All your files should end with a new line (why?)
The first line of all your files should be exactly #!/bin/bash
A README.md file, at the root of the folder of the project, describing what each script is doing
You are not allowed to use backticks, &&, || or ;
All your files must be executable

Quiz questions

Question #0

Which command should I use for changing a file permission?

chgrp
su
chmod
chown

Question #1

What is the permission value for a file read only for the group owner?

070
040
050
060

Question #2

Which command should I use for changing a file owner?

chgrp
su
chmod
chown

Question #3

What is the permission value for a file without any restriction?

600
644
777

Question #4

What is the numerical value for the rwx------ permission?

700
600
621
704

Question #5

What is the numerical value for the ----w---x permission?

021
123
121
221

Question #6

What is the numerical value for the r-xr--r-- permission?

411
522
544
644

Tasks

0. My name is Betty

Create a script that switches the current user to the user betty.

You should use exactly 8 characters for your command (+1 character for the new line)
You can assume that the user betty will exist when we will run your script

julien@ubuntu:/tmp/h$ tail -1 0-iam_betty | wc -c
9
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 0-iam_betty

1. Who am I

Write a script that prints the effective username of the current user.

julien@ubuntu:/tmp/h$ ./1-who_am_i
julien
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 1-who_am_i

2. Groups

Write a script that prints all the groups the current user is part of.

julien@ubuntu:/tmp/h$ ./2-groups
julien adm cdrom sudo dip plugdev lpadmin sambashare
julien@ubuntu:/tmp/h$

Note: depending on the user, you will get a different output.

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 2-groups

3. New owner

Write a script that changes the owner of the file hello to the user betty.

julien@ubuntu:/tmp/h$ ls -l
total 4
-rwxrw-r-- 1 julien julien 30 Sep 20 14:23 3-new_owner
-rw-rw-r-- 1 julien julien  0 Sep 20 14:18 hello
julien@ubuntu:/tmp/h$ sudo ./3-new_owner
julien@ubuntu:/tmp/h$ ls -l
total 4
-rwxrw-r-- 1 julien julien 30 Sep 20 14:23 3-new_owner
-rw-rw-r-- 1 betty  julien  0 Sep 20 14:18 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 3-new_owner

4. Empty!

Write a script that creates an empty file called hello.

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 4-empty

5. Execute

Write a script that adds execute permission to the owner of the file hello.

The file hello will be in the working directory

julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 28 Sep 20 14:26 5-execute
-rw-rw-r-- 1 julien julien 23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$ ./hello
bash: ./hello: Permission denied
julien@ubuntu:/tmp/h$ ./5-execute
julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 28 Sep 20 14:26 5-execute
-rwxrw-r-- 1 julien julien 23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 5-execute

6. Multiple permissions

Write a script that adds execute permission to the owner and the group owner, and read permission to other users, to the file hello.

The file hello will be in the working directory

julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 36 Sep 20 14:31 6-multiple_permissions
-r--r----- 1 julien julien 23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$ ./6-multiple_permissions
julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 36 Sep 20 14:31 6-multiple_permissions
-r-xr-xr-- 1 julien julien 23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 6-multiple_permissions

7. Everybody!

Write a script that adds execution permission to the owner, the group owner and the other users, to the file hello

The file hello will be in the working directory
You are not allowed to use commas for this script

julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 28 Sep 20 14:35 7-everybody
-rw-r----- 1 julien julien 23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$ ./7-everybody
julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 28 Sep 20 14:35 7-everybody
-rwxr-x--x 1 julien julien 23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 7-everybody

8. James Bond

Write a script that sets the permission to the file hello as follows:

Owner: no permission at all
Group: no permission at all
Other users: all the permissions

The file hello will be in the working directory You are not allowed to use commas for this script

julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 28 Sep 20 14:40 8-James_Bond
-rwxr-x--x 1 julien julien 23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$ ./8-James_Bond
julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 28 Sep 20 14:40 8-James_Bond
-------rwx 1 julien julien 23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 8-James_Bond

9. John Doe

Write a script that sets the mode of the file hello to this:

-rwxr-x-wx 1 julien julien 23 Sep 20 14:25 hello

The file hello will be in the working directory
You are not allowed to use commas for this script

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 9-John_Doe

10. Look in the mirror

Write a script that sets the mode of the file hello the same as olleh’s mode.

The file hello will be in the working directory
The file olleh will be in the working directory

julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 42 Sep 20 14:45 10-mirror_permissions
-rwxr-x-wx 1 julien julien 23 Sep 20 14:25 hello
-rw-rw-r-- 1 julien julien  0 Sep 20 14:43 olleh
julien@ubuntu:/tmp/h$ ./10-mirror_permissions
julien@ubuntu:/tmp/h$ ls -l
total 8
-rwxrw-r-- 1 julien julien 42 Sep 20 14:45 10-mirror_permissions
-rw-rw-r-- 1 julien julien 23 Sep 20 14:25 hello
-rw-rw-r-- 1 julien julien  0 Sep 20 14:43 olleh
julien@ubuntu:/tmp/h$

Note: the mode of olleh will not always be 664. Make sure your script works for any mode.

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 10-mirror_permissions

11. Directories

Create a script that adds execute permission to all subdirectories of the current directory for the owner, the group owner and all other users.

Regular files should not be changed.

julien@ubuntu:/tmp/h$ ls -l
total 20
-rwxrwxr-x 1 julien julien   24 Sep 20 14:53 11-directories_permissions
drwx------ 2 julien julien 4096 Sep 20 14:49 dir0
drwx------ 2 julien julien 4096 Sep 20 14:49 dir1
drwx------ 2 julien julien 4096 Sep 20 14:49 dir2
-rw-rw-r-- 1 julien julien   23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$ ./11-directories_permissions
julien@ubuntu:/tmp/h$ ls -l
total 20
-rwxrwxr-x 1 julien julien   24 Sep 20 14:53 11-directories_permissions
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir0
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir1
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir2
-rw-rw-r-- 1 julien julien   23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 11-directories_permissions

12. More directories

Create a script that creates a directory called my_dir with permissions 751 in the working directory.

julien@ubuntu:/tmp/h$ ls -l
total 20
-rwxrwxr-x 1 julien julien   39 Sep 20 14:59 12-directory_permissions
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir0
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir1
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir2
-rw-rw-r-- 1 julien julien   23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$ ./12-directory_permission s
julien@ubuntu:/tmp/h$ ls -l
total 24
-rwxrwxr-x 1 julien julien   39 Sep 20 14:59 12-directory_permissions
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir0
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir1
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir2
drwxr-x--x 2 julien julien 4096 Sep 20 14:59 my_dir
-rw-rw-r-- 1 julien julien   23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 12-directory_permissions

13. Change group

Write a script that changes the group owner to school for the file hello

The file hello will be in the working directory

julien@ubuntu:/tmp/h$ ls -l
total 24
-rwxrwxr-x 1 julien julien   34 Sep 20 15:03 13-change_group
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir0
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir1
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir2
drwxr-x--x 2 julien julien 4096 Sep 20 14:59 my_dir
-rw-rw-r-- 1 julien julien   23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$ sudo ./13-change_group
julien@ubuntu:/tmp/h$ ls -l
total 24
-rwxrwxr-x 1 julien julien      34 Sep 20 15:03 13-change_group
drwx--x--x 2 julien julien    4096 Sep 20 14:49 dir0
drwx--x--x 2 julien julien    4096 Sep 20 14:49 dir1
drwx--x--x 2 julien julien    4096 Sep 20 14:49 dir2
drwxr-x--x 2 julien julien    4096 Sep 20 14:59 my_dir
-rw-rw-r-- 1 julien school   23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 13-change_group

14. Owner and group

Write a script that changes the owner to vincent and the group owner to staff for all the files and directories in the working directory.

julien@ubuntu:/tmp/h$ ls -l
total 24
-rwxrwxr-x 1 julien julien   36 Sep 20 15:06 100-change_owner_and_group
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir0
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir1
drwx--x--x 2 julien julien 4096 Sep 20 14:49 dir2
drwxr-x--x 2 julien julien 4096 Sep 20 14:59 my_dir
-rw-rw-r-- 1 julien julien   23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$ sudo ./100-change_owner_and_group
julien@ubuntu:/tmp/h$ ls -l
total 24
-rwxrwxr-x 1 vincent staff   36 Sep 20 15:06 100-change_owner_and_group
drwx--x--x 2 vincent staff 4096 Sep 20 14:49 dir0
drwx--x--x 2 vincent staff 4096 Sep 20 14:49 dir1
drwx--x--x 2 vincent staff 4096 Sep 20 14:49 dir2
drwxr-x--x 2 vincent staff 4096 Sep 20 14:59 my_dir
-rw-rw-r-- 1 vincent staff   23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 100-change_owner_and_group

15. Symbolic links

Write a script that changes the owner and the group owner of _hello to vincent and staff respectively.

The file _hello is in the working directory
The file _hello is a symbolic link

julien@ubuntu:/tmp/h$ ls -l
total 24
-rwxrwxr-x 1 julien julien   44 Sep 20 15:12 101-symbolic_link_permissions
-rw-rw-r-- 1 julien julien   23 Sep 20 14:25 hello
lrwxrwxrwx 1 julien julien    5 Sep 20 15:10 _hello -> hello
julien@ubuntu:/tmp/h$ sudo ./101-symbolic_link_permissions
julien@ubuntu:/tmp/h$ ls -l
total 24
-rwxrwxr-x 1 julien julien      44 Sep 20 15:12 101-symbolic_link_permissions
-rw-rw-r-- 1 julien julien      23 Sep 20 14:25 hello
lrwxrwxrwx 1 vincent  staff    5 Sep 20 15:10 _hello -> hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 101-symbolic_link_permissions

16. If only

Write a script that changes the owner of the file hello to betty only if it is owned by the user guillaume.

The file hello will be in the working directory

julien@ubuntu:/tmp/h$ ls -l
total 24
-rwxrwxr-x 1 julien    julien      47 Sep 20 15:18 102-if_only
-rw-rw-r-- 1 guillaume julien      23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$ sudo ./102-if_only
julien@ubuntu:/tmp/h$ ls -l
total 24
-rwxrwxr-x 1 julien julien      47 Sep 20 15:18 102-if_only
-rw-rw-r-- 1 betty  julien      23 Sep 20 14:25 hello
julien@ubuntu:/tmp/h$

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 102-if_only

17. Star Wars

Write a script that will play the StarWars IV episode in the terminal.

Repo:

GitHub repository: alx-system_engineering-devops
Directory: 0x01-shell_permissions
File: 103-Star_Wars

Files

README.md

Latest commit

History

README.md

File metadata and controls

About Bash projects

Concepts

Resources

man or help:

Learning Objectives

Permissions

Other Man Pages

Requirements

General

Quiz questions

Question #0

Question #1

Question #2

Question #3

Question #4

Question #5

Question #6

Tasks

0. My name is Betty

1. Who am I

2. Groups

3. New owner

4. Empty!

5. Execute

6. Multiple permissions

7. Everybody!

8. James Bond

9. John Doe

10. Look in the mirror

11. Directories

12. More directories

13. Change group

14. Owner and group

15. Symbolic links

16. If only

17. Star Wars