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README.md

0x00. Shell, basics

  • By Julien Barbier
  • Weight: 1

About Bash projects

Unless stated, all your projects will be auto-corrected with Ubuntu 14.04 LTS.

Resources

Read or watch:

man or help:

  • cd
  • ls
  • pwd
  • less
  • file
  • ln
  • cp
  • mv
  • rm
  • mkdir
  • type
  • which
  • help
  • man

Learning Objectives

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

General

  • What does RTFM mean?
  • What is a Shebang

What is the Shell

  • What is the shell
  • What is the difference between a terminal and a shell
  • What is the shell prompt
  • How to use the history (the basics)

Navigation

  • What do the commands or built-ins cd, pwd, ls do
  • How to navigate the filesystem
  • What are the . and .. directories
  • What is the working directory, how to print it and how to change it
  • What is the root directory
  • What is the home directory, and how to go there
  • What is the difference between the root directory and the home directory of the user root
  • What are the characteristics of hidden files and how to list them
  • What does the command cd - do

Looking Around

  • What do the commands ls, less, file do
  • How do you use options and arguments with commands
  • Understand the ls long format and how to display it
  • A Guided Tour
  • What does the ln command do
  • What do you find in the most common/important directories
  • What is a symbolic link
  • What is a hard link
  • What is the difference between a hard link and a symbolic link

Manipulating Files

  • What do the commands cp, mv, rm, mkdir do
  • What are wildcards and how do they work
  • How to use wildcards

Working with Commands

  • What do type, which, help, man commands do
  • What are the different kinds of commands
  • What is an alias
  • When do you use the command help instead of man

Reading Man Pages

  • How to read a man page
  • What are man page sections
  • What are the section numbers for User commands, System calls and Library functions

Keyboard Shortcuts for Bash

  • Common shortcuts for Bash

LTS

  • What does LTS mean?

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 repo, containing a description of the repository
  • A README.md file, at the root of the folder of this project, describing what each script is doing
  • You are not allowed to use backticks, &&, || or ;
  • All your scripts must be executable. To make your file executable, use the chmod command: chmod u+x file. Later, we'll learn more about how to utilize this command.

More Info

Example of line count and first line

julien@ubuntu:/tmp$ wc -l 12-file_type
2 12-file_type
julien@ubuntu:/tmp$ head -n 1 12-file_type
#!/bin/bash
julien@ubuntu:/tmp$

In order to test your scripts, you will need to use this command: chmod u+x file. We will see later what does chmod mean and do, but you can have a look at man chmod if you are curious.

Example

julien@ubuntu:/tmp$ ls
12-file_type
lll
julien@ubuntu:/tmp$ ls -la lll
-rw-rw-r-- 1 julien julien 15 Sep 19 21:05 lll
julien@ubuntu:/tmp$ cat lll
#!/bin/bash
ls
julien@ubuntu:/tmp$ ls -l lll
-rw-rw-r-- 1 julien julien 15 Sep 19 21:05 lll
julien@ubuntu:/tmp$ chmod u+x lll # you do not have to understand this yet
julien@ubuntu:/tmp$ ls -l lll
-rwxrw-r-- 1 julien julien 15 Sep 19 21:05 lll
julien@ubuntu:/tmp$ ./lll
12-file_type
lll
julien@ubuntu:/tmp$

Description

Shell basic manipulation exercises are stored here

Structure

  • 0-current_working-directory prints the absolute path name of the current working directory.
  • 1-listit Display the contents list of your current directory.
  • 2-bring_me_home changes the working directory to the user’s home directory.
  • 3-listfiles Display current directory contents in a long format
  • 4-listmorefiles Display current directory contents, including hidden files
  • 5-listfilesdigitonly Display current directory contents. * Long format * with user and group IDs displayed numerically * And hidden files (starting with .)
  • 6-firstdirectory creates a directory named my_first_directory in the /tmp/ directory.
  • 7-movethatfile Move the file betty from /tmp/ to /tmp/my_first_directory.
  • 8-firstdelete : delete file betty
  • 9-firstdirdeletion : delete directory holberton in tmp directory
  • 10-back : changes working directory to previous one
  • 11-lists : list all files in the current directory, parent directory and he boot directory including hidden files in long format
  • 12-file_type : prints the type of the file iamfile in tmp directory
  • 13-symbolic_link : creates a symbolic link named ls to /bin/ls
  • 14-copy_html : copies all HTML files from working to parent directory that does not exist
  • 15-lets_move : moves all files beginning with uppercase letter to tmp directory
  • 16-clean_emacs : deletes all files ending with "~" in working directory
  • 17-tree : creates series of directories
  • 18-commas : list files and directories of current directory ending with slash(/), sorted numerically and alphabetically, and include hidden files

Tasks

0. Where am I?

mandatory

Score: 100.00% (Checks completed: 100.00%)

Write a script that prints the absolute path name of the current working directory.

Example:

$ ./0-current_working_directory
/root/alx-system_engineering-devops/0x00-shell_basics
$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 0-current_working_directory

Done! Help Re-check your code Get a sandbox QA Review

1. What's in there?

mandatory

Score: 100.00% (Checks completed: 100.00%)

Display the contents list of your current directory.

Example:

$ ./1-listit
Applications    Documents   Dropbox Movies Pictures
Desktop Downloads   Library Music Public
$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 1-listit

Done! Help Re-check your code Get a sandbox QA Review

2. There is no place like home

mandatory

Score: 100.00% (Checks completed: 100.00%)

Write a script that changes the working directory to the user's home directory.

  • You are not allowed to use any shell variables
julien@ubuntu:/tmp$ pwd
/tmp
julien@ubuntu:/tmp$ echo $HOME
/home/julien
julien@ubuntu:/tmp$ source ./2-bring_me_home
julien@ubuntu:~$ pwd
/home/julien
julien@ubuntu:~$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 2-bring_me_home

Done! Help Re-check your code Get a sandbox QA Review

3. The long format

mandatory

Score: 100.00% (Checks completed: 100.00%)

Display current directory contents in a long format

Example:

$ ./3-listfiles
total 32
-rwxr-xr-x@ 1 sylvain staff 18 Jan 25 00:19 0-current_working_directory
-rwxr-xr-x@ 1 sylvain staff 19 Jan 25 00:23 1-listit
-rwxr-xr-x@ 1 sylvain staff 18 Jan 25 00:29 2-bring_me_home
-rwxr-xr-x@ 1 sylvain staff 18 Jan 25 00:39 3-listfiles
$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 3-listfiles

Done! Help Re-check your code Get a sandbox QA Review

4. Hidden files

mandatory

Score: 100.00% (Checks completed: 100.00%)

Display current directory contents, including hidden files (starting with .). Use the long format.

Example:

$ ./4-listmorefiles
total 32
drwxr-xr-x@ 6 sylvain staff 204 Jan 25 00:29 .
drwxr-xr-x@ 43 sylvain staff 1462 Jan 25 00:19 ..
-rwxr-xr-x@ 1 sylvain staff 18 Jan 25 00:19 0-current_working_directory
-rwxr-xr-x@ 1 sylvain staff 19 Jan 25 00:23 1-listit
-rwxr-xr-x@ 1 sylvain staff 18 Jan 25 00:29 2-bring_me_home
-rwxr-xr-x@ 1 sylvain staff 18 Jan 25 00:39 3-listfiles
-rwxr-xr-x@ 1 sylvain staff 18 Jan 25 00:41 4-listmorefiles
$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 4-listmorefiles

Done! Help Re-check your code Get a sandbox QA Review

5. I love numbers

mandatory

Score: 100.00% (Checks completed: 100.00%)

Display current directory contents.

  • Long format
  • with user and group IDs displayed numerically
  • And hidden files (starting with .)

Example:

$ ./5-listfilesdigitonly
total 32
drwxr-xr-x@ 6 501 20 204 Jan 25 00:29 .
drwxr-xr-x@ 43 501 20 1462 Jan 25 00:19 ..
-rwxr-xr-x@ 1 501 20 18 Jan 25 00:19 0-current_working_directory
-rwxr-xr-x@ 1 501 20 18 Jan 25 00:23 1-listfiles
-rwxr-xr-x@ 1 501 20 19 Jan 25 00:29 2-bring_me_home
-rwxr-xr-x@ 1 501 20 20 Jan 25 00:39 3-listfiles
-rwxr-xr-x@ 1 501 20 18 Jan 25 00:41 4-listmorefiles
-rwxr-xr-x@ 1 501 20 18 Jan 25 00:43 5-listfilesdigitonly
$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 5-listfilesdigitonly

Done! Help Re-check your code Get a sandbox QA Review

6. Welcome

mandatory

Score: 100.00% (Checks completed: 100.00%)

Create a script that creates a directory named my_first_directory in the /tmp/ directory.

Example:

$ ./6-firstdirectory
$ file /tmp/my_first_directory/
/tmp/my_first_directory/: directory
$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 6-firstdirectory

Done! Help Re-check your code Get a sandbox QA Review

7. Betty in my first directory

mandatory

Score: 100.00% (Checks completed: 100.00%)

Move the file betty from /tmp/ to /tmp/my_first_directory.

Example:

$ ./7-movethatfile
$ ls /tmp/my_first_directory/
betty
$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 7-movethatfile

Done! Help Re-check your code Get a sandbox QA Review

8. Bye bye Betty

mandatory

Score: 100.00% (Checks completed: 100.00%)

Delete the file betty.

  • The file betty is in /tmp/my_first_directory

Example:

$ ./8-firstdelete
$ ls /tmp/my_first_directory/
$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 8-firstdelete

Done! Help Re-check your code Get a sandbox QA Review

9. Bye bye My first directory

mandatory

Score: 100.00% (Checks completed: 100.00%)

Delete the directory my_first_directory that is in the /tmp directory.

Example:

$ ./9-firstdirdeletion
$ file /tmp/my_first_directory
/tmp/my_first_directory: cannot open `/tmp/my_first_directory' (No such file or directory)
$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 9-firstdirdeletion

Done! Help Re-check your code Get a sandbox QA Review

10. Back to the future

mandatory

Score: 100.00% (Checks completed: 100.00%)

Write a script that changes the working directory to the previous one.

julien@ubuntu:/tmp$ pwd
/tmp
julien@ubuntu:/tmp$ cd /var
julien@ubuntu:/var$ pwd
/var
julien@ubuntu:/var$ source ./10-back
/tmp
julien@ubuntu:/tmp$ pwd
/tmp

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 10-back

Done! Help Re-check your code Get a sandbox QA Review

11. Lists

mandatory

Score: 100.00% (Checks completed: 100.00%)

Write a script that lists all files (even ones with names beginning with a period character, which are normally hidden) in the current directory and the parent of the working directory and the /boot directory (in this order), in long format.

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 11-lists

Done! Help Re-check your code Get a sandbox QA Review

12. File type

mandatory

Score: 100.00% (Checks completed: 100.00%)

Write a script that prints the type of the file named iamafile. The file iamafile will be in the /tmp directory when we will run your script.

Example

ubuntu@ip-172-31-63-244:~$ ./12-file_type
/tmp/iamafile: ELF 64-bit LSB  executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=bd39c07194a778ccc066fc963ca152bdfaa3f971, stripped

Note that depending on the file, the output of your script will be different.

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 12-file_type

Done! Help Re-check your code Get a sandbox QA Review

13. We are symbols, and inhabit symbols

mandatory

Score: 100.00% (Checks completed: 100.00%)

Create a symbolic link to /bin/ls, named __ls__. The symbolic link should be created in the current working directory.

ubuntu@ip-172-31-63-244:/tmp/sym$ ls -la
total 144
drwxrwxr-x  2 ubuntu ubuntu   4096 Sep 20 03:24 .
drwxrwxrwt 12 root   root   139264 Sep 20 03:24 ..
ubuntu@ip-172-31-63-244:/tmp/sym$./13-symbolic_link
ubuntu@ip-172-31-63-244:/tmp/sym$ ls -la
total 144
drwxrwxr-x  2 ubuntu ubuntu   4096 Sep 20 03:24 .
drwxrwxrwt 12 root   root   139264 Sep 20 03:24 ..
lrwxrwxrwx  1 ubuntu ubuntu      7 Sep 20 03:24 __ls__ -> /bin/ls

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 13-symbolic_link

Done! Help Re-check your code Get a sandbox QA Review

14. Copy HTML files

mandatory

Score: 100.00% (Checks completed: 100.00%)

Create a script that copies all the HTML files from the current working directory to the parent of the working directory, but only copy files that did not exist in the parent of the working directory or were newer than the versions in the parent of the working directory.

You can consider that all HTML files have the extension .html

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 14-copy_html

Done! Help Re-check your code Get a sandbox QA Review

15. Let's move

#advanced

Score: 100.00% (Checks completed: 100.00%)

Create a script that moves all files beginning with an uppercase letter to the directory /tmp/u.

You can assume that the directory /tmp/u will exist when we will run your script

ubuntu@ip-172-31-63-244:/tmp/sym$ ls -la
total 148
drwxrwxr-x  3 ubuntu ubuntu   4096 Sep 20 03:33 .
drwxrwxrwt 12 root   root   139264 Sep 20 03:26 ..
-rw-rw-r--  1 ubuntu ubuntu      0 Sep 20 03:32 My_file
lrwxrwxrwx  1 ubuntu ubuntu      7 Sep 20 03:24 __ls__ -> /bin/ls
-rw-rw-r--  1 ubuntu ubuntu      0 Sep 20 03:32 Elif_ym
-rw-rw-r--  1 ubuntu ubuntu      0 Sep 20 03:32 random_file
ubuntu@ip-172-31-63-244:/tmp/sym$ ls -la /tmp/u
total 8
drwxrwxr-x 2 ubuntu ubuntu 4096 Sep 20 03:33 .
drwxrwxr-x 3 ubuntu ubuntu 4096 Sep 20 03:33 ..
ubuntu@ip-172-31-63-244:/tmp/sym$ ./100-lets_move
ubuntu@ip-172-31-63-244:/tmp/sym$ ls -la
total 148
drwxrwxr-x  3 ubuntu ubuntu   4096 Sep 20 03:33 .
drwxrwxrwt 12 root   root   139264 Sep 20 03:26 ..
lrwxrwxrwx  1 ubuntu ubuntu      7 Sep 20 03:24 __ls__ -> /bin/ls
-rw-rw-r--  1 ubuntu ubuntu      0 Sep 20 03:32 random_file
ubuntu@ip-172-31-63-244:/tmp/sym$ ls -la /tmp/u
total 8
drwxrwxr-x 2 ubuntu ubuntu 4096 Sep 20 03:33 .
drwxrwxr-x 3 ubuntu ubuntu 4096 Sep 20 03:33 ..
-rw-rw-r-- 1 ubuntu ubuntu    0 Sep 20 03:32 My_file
-rw-rw-r-- 1 ubuntu ubuntu    0 Sep 20 03:32 Elif_ym

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 100-lets_move

Done! Help Re-check your code Get a sandbox QA Review

16. Clean Emacs

#advanced

Score: 100.00% (Checks completed: 100.00%)

Create a script that deletes all files in the current working directory that end with the character ~.

ubuntu@ip-172-31-63-244:/tmp/sym$ ls
main.c  main.c~  Makefile~
ubuntu@ip-172-31-63-244:/tmp/sym$ ./101-clean_emacs
ubuntu@ip-172-31-63-244:/tmp/emacs$ ls
main.c
ubuntu@ip-172-31-63-244:/tmp/emacs$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 101-clean_emacs

Done! Help Re-check your code Get a sandbox QA Review

17. Tree

#advanced

Score: 100.00% (Checks completed: 100.00%)

Create a script that creates the directories welcome/, welcome/to/ and welcome/to/school in the current directory.

You are only allowed to use two spaces (and lines) in your script, not more.

julien@ubuntu:/tmp/h$ ls -l
total 4
-rwxrw-r-- 1 julien julien 44 Sep 20 12:09 102-tree
julien@ubuntu:/tmp/h$ wc -l 102-tree
2 102-tree
julien@ubuntu:/tmp/h$ head -1 102-tree
#!/bin/bash
julien@ubuntu:/tmp/h$ tr -cd ' ' < 102-tree | wc -c # you do not have to understand this yet, but the result should be 2, 1 or 0
2
julien@ubuntu:/tmp/h$ ./102-tree
julien@ubuntu:/tmp/h$ ls
102-tree  welcome
julien@ubuntu:/tmp/h$ ls welcome/
to
julien@ubuntu:/tmp/h$ ls -l welcome/to
total 4
drwxrwxr-x 2 julien julien 4096 Sep 20 12:11 school
julien@ubuntu:/tmp/h$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 102-tree

Done! Help Re-check your code Get a sandbox QA Review

18. Life is a series of commas, not periods

#advanced

Score: 100.00% (Checks completed: 100.00%)

Write a command that lists all the files and directories of the current directory, separated by commas (,).

  • Directory names should end with a slash (/)

  • Files and directories starting with a dot (.) should be listed

  • The listing should be alpha ordered, except for the directories . and .. which should be listed at the very beginning

  • Only digits and letters are used to sort; Digits should come first

  • You can assume that all the files we will test with will have at least one letter or one digit

  • The listing should end with a new line

ubuntu@ubuntu:~/$ ls -a

.  ..  0-commas  0-commas-checks  1-empty_casks  2-gifs  3-directories  4-zeros  5-rot13  6-odd  7-sort_rot13  Makefile  quote  .test  test_dir  test.var

ubuntu@ubuntu:~/$ ./103-commas

./, ../, 0-commas, 0-commas-checks/, 1-empty_casks, 2-gifs, 3-directories, 4-zeros, 5-rot13, 6-odd, 7-sort_rot13, Makefile, quote, .test, test_dir/, test.var

ubuntu@ubuntu:~/$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: 103-commas

Done! Help Re-check your code Get a sandbox QA Review

19. File type: School

#advanced

Score: 100.00% (Checks completed: 100.00%)

Create a magic file school.mgc that can be used with the command file to detect School data files. School data files always contain the string SCHOOL at offset 0.

ubuntu@ip-172-31-63-244:/tmp/magic$ cp /bin/ls .
ubuntu@ip-172-31-63-244:/tmp/magic$ ls -la
total 268
drwxrwxr-x  2 ubuntu ubuntu   4096 Sep 20 02:44 .
drwxrwxrwt 11 root   root   139264 Sep 20 02:44 ..
-rw-r--r--  1 ubuntu ubuntu    496 Sep 20 02:42 holberton.mgc
-rwxr-xr-x  1 ubuntu ubuntu 110080 Sep 20 02:43 ls
-rw-rw-r--  1 ubuntu ubuntu     50 Sep 20 02:06 thisisanholbertonfile
-rw-rw-r--  1 ubuntu ubuntu     30 Sep 20 02:16 thisisatextfile
ubuntu@ip-172-31-63-244:/tmp/magic$ file --mime-type -m school.mgc *
school.mgc:         application/octet-stream
ls:                    application/octet-stream
thisisaschoolfile: School
thisisatextfile:       text/plain
ubuntu@ip-172-31-63-244:/tmp/magic$ file -m school.mgc *
school.mgc:         data
ls:                    data
thisisaschoolfile: School data
thisisatextfile:       ASCII text
ubuntu@ip-172-31-63-244:/tmp/magic$

Repo:

  • GitHub repository: alx-system_engineering-devops
  • Directory: 0x00-shell_basics
  • File: school.mgc