SIMPLE UNIX SHELL 🐚

Description 📃

This is a simple implementation of a UNIX command line interpreter. The shell can interpret and execute command line arguments read from the standard input. the shell read lines from a file or terminal line which is then interpreted and executed if the command is valid

Requirements

All the files are to be compiled on an Ubuntu 14.04 LTS machine with: gcc -Wall -Werror -Wextra -pedantic *.c
All files ends end with a new line, with no memory leaks
All code will use the Betty style. It will be checked using betty-style.pl and betty-doc.pl
All code will be tested using the test files in the test folder.
The simple shell supports most shell commands, such as cat, pwd, ls -la and more.

Return Value :

The shell returns a value of 0 if the command is valid and the command is executed successfully.

Output 📁

The 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 the argv[0]

Usage

list of fucntions and system calls used

- 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)
- 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

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

Testing

The shell works 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
$

Mandatory Tasks

0. Betty would be proud

Write a beautiful code that passes the Betty checks

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 execve will be the core part of your Shell, don’t forget to pass the environ to it…

3. Simple shell 0.3

Simple shell 0.2 +

Handle the PATH fork must not be called if the command doesn’t exist

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

5. Simple shell 1.0

Simple shell 0.4 +

Implement the env built-in, that prints the current environment

end of mandatory

Advanced Tasks

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

7. Simple shell 0.2.1

Simple shell 0.2 +

You are not allowed to use strtok

8. Simple shell 0.4.1

Simple shell 0.4 +

handles arguments for a 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 $?
98
julien@ubuntu:~/shell$

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

10. cd

Simple sell 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

11. `;`

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@~$

12. `&&` and `||`

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@~$

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

14. Variables

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$

15. Comments

Simple shell 1.0 +

Handle comments (#)

julien@ubuntu:~/shell$ sh
$ echo $$ # ls -la
5114
$ exit
julien@ubuntu:~/shell$

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

Contributors 👫

Giwa Abdulbasit

Ayilara Aisha

giwabasit17/simple_shell

SIMPLE UNIX SHELL 🐚

Description 📃

Requirements

Return Value :

Output 📁

Usage

list of fucntions and system calls used

Compilation

Testing

Mandatory Tasks

0. Betty would be proud

1. Simple shell 0.1

3. Simple shell 0.3

4. Simple shell 0.4

5. Simple shell 1.0

Advanced Tasks

6. Simple shell 0.1.1

7. Simple shell 0.2.1

8. Simple shell 0.4.1

9. setenv, unsetenv

10. cd

11. ;

12. && and ||

13. alias

14. Variables

15. Comments

16. File as input

Contributors 👫

11. `;`

12. `&&` and `||`