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Simple Shell

What the code is about:

It is a simple shell

What is a Shell?

A Shell is a program that takes the command from the user through the standsrd input, the keyboard, and passes them along to the machine to execute them through the kernel.

How does a shell work?

Basically, a shell performs four main tasks:Read, parse, execute and loop (RPEL). In performing any of its tasks, a shell can function in either interactive way, or non-interactive way. The interactive mode is where the user types inbsome commandwhile the shell wait to recieve, process and execute these commands. On the other hand, the non-interactive mode is a way a user wants the shell to perform action using bash script or run a program through an automated process.

Basic Shell Commands

The basic commands in shell are the following: ls, cd, pwd and echo

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

The shell will be compiled with:

gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh

Testing

The 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
$