README.md File

0x16.C-Simple Shell README.md File

This is a team project on 0x16. C - Simple Shell

• Done by:
  • Bereket Dereje Mekonnen

• File_name:
  • README.md file
• Created:
  • On November 3, 2023
• Author:
  • Bereket Dereje Mekonnen,
• Project:
  • 0x16. C - Simple Shell
• GitHub repository:
  • simple_shell
• Directory:
  • simple_shell
• Project Tasks:
  • Mandatory and Advanced
• Tasks in number:
  • 17 Tasks (6-Mandatory & 11-Advanced)
• Mandatory_Tasks:
  • From Task 0 to 5
• Advanced_Tasks:
  • From Task 6 to 16

PROJECT_TITLE:

0x16.C-Simple Shell

GITHUB_REPOSITORY:

simple_shell

Background Context

• Write a simple UNIX command interpreter.

My Simple Shell Files

Table of My Simple Shell Project Files

My Simple Shell Project Files
	NO.	File Name		NO.	File Name		NO.	File Name
	1	README.md		12	char_err.c		23	sep_list.c
	2	shell.h		13	synt_err.c		24	line_list.c
	3	shell.c		14	env.c		25	rvar_list.c
	4	_getbuiltin.c		15	environ.c		26	readline.c
	5	_geterror.c		16	err.c		27	memo.c
	6	_gethelp.c		17	error.c		28	var.c
	7	_getline.c		18	exec.c		29	comm.c
	8	_getsigint.c		19	exit_shell.c		30	conv.c
	9	exec_line.c		20	help_env.c		31	_strcc.c
	10	cd_shell.c		21	help_gen.c		32	_strdlt.c
	11	cddir.c		22	shell_loop.c		33	hsh

Exercise Files
	NO.	File Name		NO.	File Name		NO.	File Name
	1	_getenv.c		17	fork0.c		33	shell.c
	2	add.c		18	fork0_0.c		34	shell_0.3.c
	3	add1.c		19	fork0_1.c		35	stat.c
	4	add2.c		20	fork_1.c		36	strtok.c
	5	env-main.c		21	fork_my_fork.c		37	strtok1.c
	6	env_vs_environ.c		22	fork_my_fork1.c		38	strtok2.c
	7	environ.c		23	fork_my_fork2.c		39	strtok3_without_strtok.c
	8	exec.c		24	fwe.c		40	strtok_1.c
	9	exec0.c		25	getenv.c		41	strtok_2.c
	10	exec1.c		26	no_argc.c		42	subtract.c
	11	exec2.c		27	path.c		43	sum.c
	12	f_w_e.c		28	pid.c		44	sum1.c
	13	f_w_e1.c		29	ppid.c		45	sum2.c
	14	f_w_e2.c		30	prompt.c		46	sum3.c
	15	find_file.c		31	prompt0.c		47	wait.c
	16	fork.c		32	prompt1.c		48	wait0.c

Learning Objectives

Learning Objectives

• At the end of this project,
  • You are expected to be able to explain to anyone,
    • Without the help of Google:

General Learning Objectives

General Learning Objectives

• Who designed and implemented the original Unix operating system
• Who wrote the first version of the UNIX shell
• Who invented the B programming language
  • (the direct predecessor to the C programming language)
• Who is Ken Thompson
• How does a shell work
• What is a pid and a ppid
• How to manipulate the environment of the current process
• What is the difference between a function and a system call
• How to create processes
• What are the three prototypes of main
• How does the shell use the PATH to find the programs
• How to execute another program with the execve system call
• How to suspend the execution of a process until one of its children terminates
• What is EOF / “end-of-file”?

Copyright - Plagiarism

• You are tasked to come up with solutions for the tasks yourself
  • To meet with the above learning objectives.
• You will not be able to meet the objectives of this or any following project
  • By copying and pasting someone else’s work.
• You are not allowed to publish any content of this project.
• Any form of plagiarism is strictly forbidden
  • And will result in removal from the program.

Requirements

General Requirements

• Allowed editors: vi, vim, emacs
• All your files will be compiled on Ubuntu 20.04 LTS using gcc,
  • using the options -Wall -Werror -Wextra -pedantic -std=gnu89
• All your files should end with a new line
• A README.md file,
  • at the root of the folder of the project is mandatory
• Your code should use the Betty style.
  • It will be checked using betty-style.pl and betty-doc.pl
• Your shell should not have any memory leaks
• No more than 5 functions per file
• All your header files should be include guarded
• Use system calls only when you need to (why?)
• Write a README with the description of your project
• You should have an AUTHORS file at the root of your repository,
  • listing all individuals
    • having contributed content to the repository.
      • Format, see Docker

GitHub Requirements

• There should be one project repository per group.
  • If you and your partner have a repository with the same name in both your accounts,
    • you risk a 0% score.
  • Add your partner as a collaborator.

PROJECT_TITLE:

0x16. C - Simple Shell

GITHUB_REPOSITORY:

simple_shell

• File_name: README.md file
• Created: On November 3, 2023
• Authors:
  • Bereket Dereje Mekonnen
• Project: 0x16. C - Simple Shell
• GitHub repository: simple_shell
• Directory: simple_shell
• Project Tasks: Mandatory and Advanced
• Tasks in number: 17 Tasks (6->Mandatory & 4->Advanced)
• Mandatory_Tasks: From Task 0 to 5
• Advanced_Tasks: From Task 6 to 16

PROJECT TASKS (Mandatory and Advanced)

MANDATORY_TASKS (From Task 0 to 5)

No. 0. Betty would be proud

• Write a beautiful code that passes the Betty checks.

No. 1. Simple shell 0.1

• Write a UNIX command line interpreter.
  • Usage: simple_shell

• Your Shell should:
  • Display a prompt and wait for the user to type a command.
    • A command line always ends with a new line.
  • The prompt is displayed again each time a command has been executed.
  • The command lines are simple, no semicolons, no pipes, no redirections or any other advanced features.
  • The command lines are made only of one word.
    • No arguments will be passed to programs.
  • If an executable cannot be found, print an error message and display the prompt again.
  • Handle errors.
  • You have to handle the “end of file” condition (Ctrl+D)

• You don’t have to:

  • use the PATH

  • implement built-ins

  • handle special characters : ", ', `, , *, &, #

  • be able to move the cursor

  • handle commands with arguments

    • From My Simple Shell Output

No. 2. Simple shell 0.2

• Simple shell 0.1 +
  • Handle command lines with arguments

No. 3. Simple shell 0.3

• Simple shell 0.2 +
  • Handle the PATH
  • fork must not be called if the command doesn’t exist
    • From My Simple Shell Output

No. 4. Simple shell 0.4

• Simple shell 0.3 +
  • Implement the exit built-in, that exits the shell
  • Usage: exit
  • You don’t have to handle any argument to the built-in exit

No. 5. Simple shell 1.0

• Simple shell 0.4 +
  • Implement the env built-in,

    • that prints the current environment

    • From My Simple Shell Output

ADVANCED_TASKS (From Task 6 to 16)

No. 6. Simple shell 0.1.1

• Simple shell 0.1 +
  • Write your own getline function
  • Use a buffer to read many chars at once and call the least possible the read system call
  • You will need to use static variables
  • You are not allowed to use getline

• You don’t have to:
  • be able to move the cursor

No. 7. Simple shell 0.2.1

• Simple shell 0.2 +
  • You are not allowed to use strtok

No. 8. Simple shell 0.4.1

• Simple shell 0.4 +

  • handle arguments for the built-in exit

  • Usage: exit status, *where status is an integer used to exit the shell

    • From My Simple Shell Output

No. 9. setenv, unsetenv

• Simple shell 1.0 +

• Implement the setenv and unsetenv builtin commands

• setenv
  • Initialize a new environment variable, or modify an existing one
  • Command syntax: setenv VARIABLE VALUE
  • Should print something on stderr on failure

• unsetenv
  • Remove an environment variable
  • Command syntax: unsetenv VARIABLE
  • Should print something on stderr on failure

No. 10. cd

• Simple shell 1.0 +
  • Implement the builtin command cd:
    • Changes the current directory of the process.
    • Command syntax: cd [DIRECTORY]
    • If no argument is given to cd the command must be interpreted like cd $HOME
    • You have to handle the command cd -
    • You have to update the environment variable PWD when you change directory

No. 11. ;

• Simple shell 1.0 +
  • Handle the commands separator ;

• From My Simple Shell Output

No. 12. && and ||

• Simple shell 1.0 +
  • Handle the && and || shell logical operators.

• From My Simple Shell Output

No. 13. alias

• Simple shell 1.0 +
  • Implement the alias builtin command
  • Usage: alias [name[='value'] ...]
    • alias:
      • Prints a list of all aliases,
      • one per line,
      • in the form name='value'
    • alias name [name2 ...]:
      • Prints the aliases name, name2, etc
      • 1 per line,
      • in the form name='value'
    • alias name='value' [...]:
      • Defines an alias for each name whose value is given.
      • If name is already an alias,
        • replaces its value with value

No. 14. Variables

• Simple shell 1.0 +

  • Handle variables replacement

  • Handle the " $? " variable

  • Handle the " $$ " variable

    • From My Simple Shell Output

No. 15. Comments

• Simple shell 1.0 +

  • Handle comments ** (#) **

    • From My Simple Shell Output

No. 16. File as input

• Simple shell 1.0 +
  • Usage:
    • simple_shell [filename]
  • Your shell can take a file as
    • a command line argument
  • The file contains all the commands
    • that your shell should run before exiting
  • The file should contain one command per line
  • In this mode,
    • the shell should not print a prompt and
    • should not read from stdin

Resources

• Read or watch:
  • Unix shell
  • Thompson shell
  • Ken Thompson
  • Everything you need to know to start coding your own shell concept page

• man or help:
  • sh (Run sh as well)

More Info

Output

• Unless specified otherwise,
  • your program must have
    • the exact same output as
      • as sh (/bin/sh)
    • as well as the exact same
      • error output.
• The only difference is
  • when you print an error,
    • the name of the program
      • must be equivalent to your argv[0].

• Example of error with sh:

  $ echo "qwerty" | /bin/sh
  /bin/sh: 1: qwerty: not found
  $ echo "qwerty" | /bin/../bin/sh
  /bin/../bin/sh: 1: qwerty: not found
  $
  

• Same error with your program hsh:

  $ echo "qwerty" | ./hsh
  ./hsh: 1: qwerty: not found
  $ echo "qwerty" | ./././hsh
  ./././hsh: 1: qwerty: not found
  $
  

List of allowed functions and system calls

• access (man 2 access)
• chdir (man 2 chdir)
• close (man 2 close)
• closedir (man 3 closedir)
• execve (man 2 execve)
• exit (man 3 exit)
• _exit (man 2 _exit)
• fflush (man 3 fflush)
• fork (man 2 fork)
• free (man 3 free)
• getcwd (man 3 getcwd)
• getline (man 3 getline)
• getpid (man 2 getpid)
• isatty (man 3 isatty)
• kill (man 2 kill)
• malloc (man 3 malloc)
• open (man 2 open)
• opendir (man 3 opendir)
• perror (man 3 perror)
• read (man 2 read)
• readdir (man 3 readdir)
• signal (man 2 signal)
• stat (__xstat) (man 2 stat)
• lstat (__lxstat) (man 2 lstat)
• fstat (__fxstat) (man 2 fstat)
• strtok (man 3 strtok)
• wait (man 2 wait)
• waitpid (man 2 waitpid)
• wait3 (man 2 wait3)
• wait4 (man 2 wait4)
• write (man 2 write)

Compilation

• Your shell will be compiled this way:
  • gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh

Testing

• Your shell should work like this in interactive mode:

         $ ./hsh
        ($) /bin/ls
         hsh main.c shell.c
        ($)
        ($) exit
         $
  

• But also in non-interactive mode:

         $ echo "/bin/ls" | ./hsh
         hsh main.c shell.c test_ls_2
         $
         $ cat test_ls_2
         /bin/ls
         /bin/ls
         $
         $ cat test_ls_2 | ./hsh
         hsh main.c shell.c test_ls_2
         hsh main.c shell.c test_ls_2
         $
  

@Checks

• The Checker will be released at the end of the project (1-2 days before the deadline).
• We strongly encourage the entire class to work together
  • to create a suite of checks covering both
    • regular tests and
    • edge cases for each task.
      • See task 8. Test suite.