0x02-shell_redirections

Shell, I/O Redirections and filter

Learning Objectives in this project:

Shell, I/O Redirection

• I familiarized myself with the commands head, tail, find, wc, sort, uniq, grep, and tr.
• I learned how to redirect standard output to a file.
• How to get standard input from a file instead of the keyboard.
• How to send the standard output from one peogram to the input of another program.
• How to combine commands and filters with redirections.

Special Characters

• I learned about special characters.
• I familiarized myself with white spaces, single quotes, doubles quotes, backslash, comments, pipe, command separator, tilde and how and when to use them

Man Pages

• I learned how to display a line of text.
• How to concantenate files and print on the standard output.
• How to reverse a string
• How to remove sections from each line of files.
• What is the /etc/passwd file and what is its format.
• What is the /etc/shadow file and what is its format.

Tasks

• 0. Hello World

  • 0-hello_world: Bash script that prints “Hello, World”, followed by a new line to the standard output.

• 1. Confused smiley

  • 1-confused_smiley: Bash script that displays a confused smiley "(Ôo)'.

• 2. Let's display a file

  • 2-hellofile: Bash script that displays the content of the /etc/passwd file.

• 3. What about 2?

  • 3-twofiles: Bash script that displays the content of /etc/passwd and /etc/hosts.

• 4. Last lines of a file

  • 4-lastlines: Bash script that displays the last 10 lines of /etc/passwd.

• 5. I'd prefer the first ones actually

  • 5-firstlines: Bash script that displays the first 10 lines of /etc/passwd.

• 6. Line #2

  • 6-third_line: Bash script that displays the third line of the file iacta.

• 7. It is a good file that cuts iron without making a noise

  • 7-file: Bash script that creates a file named exactly \*\\'"Best School"\'\\*$\?\*\*\*\*\*:) containing the text Best School ending by a new line.

• 8. Save current state of directory

  • 8-cwd_state: Bash script that writes into the file ls_cwd_content the result of the command ls -la. If the file ls_cwd_content already exists, it should be overwritten. If the file ls_cwd_content does not exist, create it.

• 9. Duplicate last line

  • 9-duplicate_last_line: Bash script that duplicates the last line of the file iacta
    • The file iacta will be in the working directory

• 10. No more javascript

  • 10-no_more_js: Bash script that deletes all the regular files (not the directories) with a .js extension that are present in the current directory and all its subfolders.

• 11. Don't just count your directories, make your directories count

  • 11-directories: Bash script that counts the number of directories and sub-directories in the current working directory.
    • The current and parent directories should not be taken into account
    • Hidden directories should be counted

• 12. What’s new

  • 12-newest_files: Bash script that displays the 10 newest files in the current directory.
    • One file per line
    • Sorted from newest to the oldest.

• 13. Being unique is better than being perfect

  • 13-unique: Bash script that takes a list of words as input and prints only words that appear exactly once.
    • Input format: One line, one word
    • Output format: One line, one word
    • Words should be sorted

• 14. It must be in that file

  • 14-findthatword: Bash script that displays lines containing the pattern "root" from the file /etc/passwd.

• 15. Count that word

  • 15-countthatword: Bash script that displays the number of lines that contain the pattern "bin" in the file /etc/passwd.

• 16. What's next?

  • 16-whatsnext: Bash script that displays lines containing the pattern "root" and 3 lines after them in the file /etc/paswd.

• 17. I hate bins

  • 17-hidethisword: Bash script that displays all the lines in the file /etc/passwd that do not contain the pattern “bin”.

• 18. Letters only please

  • 18-letteronly: Bash script that displays all lines of the file /etc/ssh/sshd_config starting with a letter.
    • Include capital letters as well

• 19. A to Z

  • 19-AZ: Bash script that replaces all characters A and C from input to z and e respectively.

• 20. Without C, you would live in hiago

  • 20-hiago: Bash script that removes all letters c and C from input.

• 21. esreveR

  • 21-reverse: Bash script that reverses its input.

• 22. DJ Cut Killer

  • 22-users_and_homes: Bash script that displays all users and their home directories, sorted bu users.
    • Based on the /etc/passwd file

• 23. Empty casks make the most noise

  • 100-empty_casks: Bash script that finds all empty files and directories in the current directory and all sub-directories.
    • Only the names of the files and directories should be displayed (not the entire path)
    • Hidden files should be listed
    • One file name per line
    • The listing should end with a new line
    • You are not allowed to use basename, grep, egrep, fgrep or rgrep

• 24. A gif is worth ten thousand words

  • 101-gifs: Bash script that lists all the files with a .gif extension in the current directory and all its sub-directories.
    • Hidden files should be listed
    • Only regular files (not directories) should be listed
    • The names of the files should be displayed without their extensions
    • The files should be sorted by byte values, but case-insensitive (file aaa should be listed before file bbb, file .b should be listed before file a, and file Rona should be listed after file jay)
    • One file name per line
    • The listing should end with a new line
    • You are not allowed to use basename, grep, egrep, fgrep or rgrep

• 25. Acrostic

  • 102-acrostic: Bash script that decodes acrostics that use the first letter of each line.
    • The ‘decoded’ message has to end with a new line
    • You are not allowed to use grep, egrep, fgrep or rgrep

• 26. The biggest fan

  • 103-the_biggest_fan: Bash script that parses web servers logs in TSV format as input and displays the 11 hosts or IP addresses which did the most requests.
    • Order by number of requests, most active host or IP at the top
    • You are not allowed to use grep, egrep, fgrep or rgrep