Minishell, recreating bash. (42 school project)

The aim of this project is to create a shell using bash (bourne-again shell) as reference.

About The Project

Minishell is a Unix shell really similar to bash but with some reduced functionalities. The project is written from scratch in C. Some of the functionalities are:

• Displays current directory when waiting for a new command.

• Working history of commands.

• Searches and launches the right executable (based on the PATH variable or using a relative or an absolute path).

• Variable expansion of environment variables, tilde characater '~' and $?.

• Single and double quotes as bash would, single quotes prevent the shell from interpreting the metacharacters in the quoted sequence.

• Redirections:

  • '<' Redirects input.
  • '>' Redirects output.
  • '<<' + DELIMITER, reads the input until a line containing the delimiter is seen. It doesn’t update the history.
  • '>>' Redirects output in append mode.

• Works with pipes '|'. The output of each command in the pipeline is connected to the input of the next command via a pipe.

• $? is updated with the exit code of the last executed command in the pipe.

• Handles signals ctrl-C, ctrl-D and ctrl-\ which behave like in bash.

• To finish, the following built-in commands were implemented from scratch:

  • echo with option -n
  • cd with only a relative or absolute path
  • pwd with no options
  • export with no options
  • unset with no options
  • env with no options or arguments
  • exit

Note

This project doesn't handle the following functionalities:

• STDERR redirection like '2>' or STDERR + STDOUT redirection like '&>'.
• Unclosed quotes. If quotes are left unclosed minishell will interpret there is a closing quote at the end of the command.
• Commands ending with a pipe character '|'. Minishell will throw a syntax error on that case.
• Logical operators like '&&' and '||'.
• Special characters like '/' and ';'.
• Wildcards '*'.

Getting Started

In order to run the program first clone the repository:

git clone git@github.com:adriapriego/minishell.git

Open the folder:

cd minishell/

Compile the program:

make

Run the program:

./minishell

Note

Additionally the executable could be moved to a directory in the $PATH to make it work from anywhere in the computer typing 'minishell', like bash.

Authors

This project is written by @ferri17 and me as part of 42 School core curriculum. I was mainly focused on the focused on the built-ins, expansor, and signals, while Ferran focused on the lexer(tokenizer), parser, and executor.