Minishell is a project in the 42 common core. The goal is to code a shell from scratch, which can handle redirections and piping, across multiple commands chained together. We used bash as a reference whenever we needed to test our shell against a real one.

For this project, we were allowed to use part of the readline library, a huge help when it comes to controlling user input.

With minishell, we learned a lot about interpreting user input (lexer/parser chain), UNIX processes (forking and connecting a process' STDIN/STDOUT), UNIX signals (handling ctrl+C, D, \), how a shell behaves internally, and more. An arduous task after only two months of programming experience at the time (three, counting the Piscine), but ultimately an enriching experience.

Here is a list of some of the features we had to implement:

• Have an input prompt, and command history.
• Have environment variables which can expand to their values when preceeded by a $.
• Handle the special $? variable, which expands to the exit code of the last command.
• Search and launch a program based on the PATH environment variable.
• Handle double quotes, inhibiting interpretation of their content except for $.
• Handle single quotes, inhibiting interpretation of their content at all.
• Handle redirections (<, <<, >, and >>) like in bash, for STDOUT.
• Handle pipes (|) like in bash, for STDOUT.
• Handle ctrl+C, ctrl+D, and ctrl+\ like in bash.

Minishell implements the following built-in commands:

• echo with the -n flag.
• cd with a relative or absolute path.
• pwd without flags.
• export without flags.
• unset without flags.
• env without flags or arguments.
• exit without flags.