This is a team project by Nandila Mulilalila and Ademola Bello

0x16. C - Simple Shell C Group project Syscall By: Julien Barbier Weight: 10 Project to be done in teams of 2 people (your team: Nandila Mulilalila, Ademola Bello) Project will start Feb 8, 2023 5:00 AM, must end by Feb 23, 2023 5:00 AM Checker will be released at Feb 22, 2023 12:12 AM An auto review will be launched at the deadline Concepts For this project, we expect you to look at these concepts:

Everything you need to know to start coding your own shell Approaching a Project Background Context Write a simple UNIX command interpreter.

^ “The Gates of Shell”, by Spencer Cheng, featuring Julien Barbier

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

General 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 below 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 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 *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. *

More Info Output Unless specified otherwise, your program must have the exact same output 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] (See below) 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.

Tasks 0. Betty would be proud mandatory Write a beautiful code that passes the Betty checks

Repo:

GitHub repository: simple_shell

1. Simple shell 0.1 mandatory 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 execve will be the core part of your Shell, don’t forget to pass the environ to it…

julien@ubuntu:/shell$ ./shell #cisfun$ ls ./shell: No such file or directory #cisfun$ /bin/ls barbie_j env-main.c exec.c fork.c pid.c ppid.c prompt prompt.c shell.c stat.c wait env-environ.c exec fork mypid ppid printenv promptc shell stat test_scripting.sh wait.c #cisfun$ /bin/ls -l ./shell: No such file or directory #cisfun$ ^[[D^[[D^[[D ./shell: No such file or directory #cisfun$ ^[[C^[[C^[[C^[[C ./shell: No such file or directory #cisfun$ exit ./shell: No such file or directory #cisfun$ ^C julien@ubuntu:/shell$ echo "/bin/ls" | ./shell barbie_j env-main.c exec.c fork.c pid.c ppid.c prompt prompt.c shell.c stat.c wait env-environ.c exec fork mypid ppid printenv promptc shell stat test_scripting.sh wait.c #cisfun$ julien@ubuntu:~/shell$ Repo:

GitHub repository: simple_shell

2. Simple shell 0.2 mandatory Simple shell 0.1 +

Handle command lines with arguments Repo:

GitHub repository: simple_shell

3. Simple shell 0.3 mandatory Simple shell 0.2 +

Handle the PATH fork must not be called if the command doesn’t exist julien@ubuntu:/shell$ ./shell_0.3 :) /bin/ls barbie_j env-main.c exec.c fork.c pid.c ppid.c prompt prompt.c shell_0.3 stat test_scripting.sh wait.c env-environ.c exec fork mypid ppid printenv promptc shell shell.c stat.c wait :) ls barbie_j env-main.c exec.c fork.c pid.c ppid.c prompt prompt.c shell_0.3 stat test_scripting.sh wait.c env-environ.c exec fork mypid ppid printenv promptc shell shell.c stat.c wait :) ls -l /tmp total 20 -rw------- 1 julien julien 0 Dec 5 12:09 config-err-aAMZrR drwx------ 3 root root 4096 Dec 5 12:09 systemd-private-062a0eca7f2a44349733e78cb4abdff4-colord.service-V7DUzr drwx------ 3 root root 4096 Dec 5 12:09 systemd-private-062a0eca7f2a44349733e78cb4abdff4-rtkit-daemon.service-ANGvoV drwx------ 3 root root 4096 Dec 5 12:07 systemd-private-062a0eca7f2a44349733e78cb4abdff4-systemd-timesyncd.service-CdXUtH -rw-rw-r-- 1 julien julien 0 Dec 5 12:09 unity_support_test.0 :) ^C julien@ubuntu:/shell$ Repo:

GitHub repository: simple_shell

4. Simple shell 0.4 mandatory 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 Repo:

GitHub repository: simple_shell

5. Simple shell 1.0 mandatory Simple shell 0.4 +

Implement the env built-in, that prints the current environment julien@ubuntu:/shell$ ./simple_shell $ env USER=julien LANGUAGE=en_US SESSION=ubuntu COMPIZ_CONFIG_PROFILE=ubuntu SHLVL=1 HOME=/home/julien C_IS=Fun_:) DESKTOP_SESSION=ubuntu LOGNAME=julien TERM=xterm-256color PATH=/home/julien/bin:/home/julien/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin DISPLAY=:0 $ exit julien@ubuntu:/shell$ Repo:

GitHub repository: simple_shell

6. Simple shell 0.1.1 #advanced 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 Repo:

GitHub repository: simple_shell

7. Simple shell 0.2.1 #advanced Simple shell 0.2 +

You are not allowed to use strtok Repo:

GitHub repository: simple_shell

8. Simple shell 0.4.1 #advanced Simple shell 0.4 +

handle arguments for the built-in exit Usage: exit status, where status is an integer used to exit the shell julien@ubuntu:/shell$ ./shell_0.4.1 $ exit 98 julien@ubuntu:/shell$ echo $? 98 julien@ubuntu:~/shell$ Repo:

GitHub repository: simple_shell

9. setenv, unsetenv #advanced 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 Repo:

GitHub repository: simple_shell

10. cd #advanced 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 man chdir, man getcwd

Repo:

GitHub repository: simple_shell

11. ; #advanced Simple shell 1.0 +

Handle the commands separator ; alex@$ ls /var ; ls /var backups cache crash lib local lock log mail metrics opt run spool tmp backups cache crash lib local lock log mail metrics opt run spool tmp alex@$ ls /hbtn ; ls /var ls: cannot access /hbtn: No such file or directory backups cache crash lib local lock log mail metrics opt run spool tmp alex@$ ls /var ; ls /hbtn backups cache crash lib local lock log mail metrics opt run spool tmp ls: cannot access /hbtn: No such file or directory alex@$ ls /var ; ls /hbtn ; ls /var ; ls /var backups cache crash lib local lock log mail metrics opt run spool tmp ls: cannot access /hbtn: No such file or directory backups cache crash lib local lock log mail metrics opt run spool tmp backups cache crash lib local lock log mail metrics opt run spool tmp alex@~$ Repo:

GitHub repository: simple_shell

12. && and || #advanced Simple shell 1.0 +

Handle the && and || shell logical operators alex@$ ls /var && ls /var backups cache crash lib local lock log mail metrics opt run spool tmp backups cache crash lib local lock log mail metrics opt run spool tmp alex@$ ls /hbtn && ls /var ls: cannot access /hbtn: No such file or directory alex@$ ls /var && ls /var && ls /var && ls /hbtn backups cache crash lib local lock log mail metrics opt run spool tmp backups cache crash lib local lock log mail metrics opt run spool tmp backups cache crash lib local lock log mail metrics opt run spool tmp ls: cannot access /hbtn: No such file or directory alex@$ ls /var && ls /var && ls /var && ls /hbtn && ls /hbtn backups cache crash lib local lock log mail metrics opt run spool tmp backups cache crash lib local lock log mail metrics opt run spool tmp backups cache crash lib local lock log mail metrics opt run spool tmp ls: cannot access /hbtn: No such file or directory alex@$ alex@$ ls /var || ls /var backups cache crash lib local lock log mail metrics opt run spool tmp alex@$ ls /hbtn || ls /var ls: cannot access /hbtn: No such file or directory backups cache crash lib local lock log mail metrics opt run spool tmp alex@$ ls /hbtn || ls /hbtn || ls /hbtn || ls /var ls: cannot access /hbtn: No such file or directory ls: cannot access /hbtn: No such file or directory ls: cannot access /hbtn: No such file or directory backups cache crash lib local lock log mail metrics opt run spool tmp alex@$ ls /hbtn || ls /hbtn || ls /hbtn || ls /var || ls /var ls: cannot access /hbtn: No such file or directory ls: cannot access /hbtn: No such file or directory ls: cannot access /hbtn: No such file or directory backups cache crash lib local lock log mail metrics opt run spool tmp alex@$ Repo:

GitHub repository: simple_shell

13. alias #advanced 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 Repo:

GitHub repository: simple_shell

14. Variables #advanced Simple shell 1.0 +

Handle variables replacement Handle the $? variable Handle the $$ variable julien@ubuntu:/shell$ ./hsh $ ls /var backups cache crash lib local lock log mail metrics opt run snap spool tmp $ echo $? 0 $ echo $$ 5104 $ echo $PATH /home/julien/bin:/home/julien/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin $ exit julien@ubuntu:/shell$ Repo:

GitHub repository: simple_shell

15. Comments #advanced Simple shell 1.0 +

Handle comments (#) julien@ubuntu:/shell$ sh $ echo $$ # ls -la 5114 $ exit julien@ubuntu:/shell$ Repo:

GitHub repository: simple_shell

16. File as input #advanced 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 Repo:

GitHub repository: simple_shell

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