What really happens when you type a command into a shell? How does it know how to run programs and interprets user inputs? Well, you are in the right pod! This project dissects the shell program that allows you to even explain to anyone without the use of the internet :) Excited? noe let's dig in!

The simple shell is an application that reads lines from either a file or the terminal, interprets them, and executes them. I most cases, it provides a command line user interface for Unix-like operating systems, where can interactively type directly to the running shell or pipe in shell scripts. read more. In this project, we designed and implemented a simple UNIX command line interpreter from the ground ^-^.

• All our files will be compiled on Ubuntu 14.04 LTS
• Our C programs and functions will be compiled with gcc 4.8.4 using the flags -Wall -Werror -Wextra and -pedantic
• Our files ends end with a new line, with no memory leaks
• Our code will use the Betty style. It will be checked using betty-style.pl and betty-doc.pl.
• system calls will be used when necessary (why?)

• Our program 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]

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

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

- 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)

You can compile our shell using:

gcc -Wall -Werror -Wextra -pedantic *.c -o hsh

Our shell should work like this in interactive mode:

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

$ 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
$

1. Write a beautiful code that passes the Betty checks
2. Write a UNIX command line interpreter.

• Display a prompt and wait for the user to type a command, ending wih 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, an error message is displayed to the user, and then display the prompt again.
• We will handle errors, including the “end of file” condition (Ctrl+D)

• Display the page

 man ./man_1_simple_shell