Thanks to Minishell, we were able to travel through time and come back to problems people faced when Windows didn’t exist.
The first bigger project in the 42 curriculum: recoding our own little bash. A program capable of parsing a prompt and launching executables with arguments, along with a few built-in functions.
MiniShell introduces us to the world of shells. It provides a convenient text interface to interact with the system. Shells might seem very easy to understand but have very specific and defined behaviour in almost every single case, most of which will need to be handled properly.
The output is still far from the original shell - especially because of the Hotfix period at the end of the project, but comes pretty close.
Thanks mvomiero for the collaboration on this project!
Screencast.Demo.minishell.webm
- how does the concept of
Lexer->Parser->Executorwork - how do I structure a bigger project to work on it in a team
- how is a shell set-up and how does it exactly work
- using known patterns such as exit status in a bigger project
- And of course how to collaborate on a project and split workload in an efficient way!
Core features of our shell are:
- as simple as it is: the same as bash :-P
- search and launch executables (with relative and absolute path)
- working history
- handle quotes and $ (dollar sign)
- redirections (<, >, <<, >>)
- pipes
- environment variables
ctrl-C,ctrl-Dandctrl-\- builtins such as echo, cd, pwd, export, unset, env, exit
- not crashing in any scenarios - sounds trivial, I know Sure, it's not a full-grown shell, but pretty close. So please bare some abstractions in the implementation.
Allowed external functions / libraries:
- readline, rl_clear_history, rl_on_new_line, rl_replace_line, rl_redisplay, add_history, printf, malloc, free, write, access, open, read, close, fork, wait, waitpid, wait3, wait4, signal, sigaction, sigemptyset, sigaddset, kill, exit, getcwd, chdir, stat, lstat, fstat, unlink, execve, dup, dup2, pipe, opendir, readdir, closedir, strerror, perror, isatty, ttyname, ttyslot, ioctl, getenv, tcsetattr, tcgetattr, tgetent, tgetflag, tgetnum, tgetstr, tgoto, tputs
- Libft - own library with basic functions such as calloc, strncpm, etc. (see submodule)
As usual: All heap allocated memory space must be properly freed. No leaks will be tolerated.
Note that the program is written with Linux. Other operating systems were not tested.
- Clone the repository and its submodule by
git clone --recursive <project SSH/URL> - direct to the cloned folder
cd <folder_name> make(automatically compiles the Libft)
Simply run the minishell without arguments:
- Example:
./minishell
Realizing this project requires a deeper understanding of the shell and the method of lexer/parser/executor. The following list is a recommendation of sources for anyone who wants to know more about the topic:
| Topic | Link |
|---|---|
| Official Bash Reference Manual (!!!) | Bash Reference Manual |
| Knowldge base and useful links | LinkTree Minishell |
| Writing Your Own Shell (extract from book) | 2014 Gustavo Rodriguez-Rivera and Justin Ennen,Introduction to Systems Programming: a Hands-on Approach |
| Shell Command Language | IEEE Std 1003.1, 2004 Edition |
| Overview from a 42 student | MiniShell |
| detailed explenation of Unix-like OS | MIT xv6: a simple, Unix-like teaching operating system |
| Tutorial: Write a Shell in C | Stephen Brennan Blog |
| Tutorial on minishell | zakaria oukaddour |
| List of possible Tests | google.docs with tests |