0x16. C - Simple Shell Project by Augustus Idiata & Chiamaka Emedo

Resources

1. Unix shell
2. Thompson shell
3. Ken Thompson
4. Everything you need to know to start coding your own shell concept page.

Learning Objectives

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

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

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 this way: 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 $