42-minishell

The objective of this project is to create a simple shell, like an own little bash.
It is the first group project in the 42 core curriculum. (tjensen42 && hepple42)

Project specifications

For the project we were allowed to use GNU's readline library which handles the terminal interaction (history & input reading). For everything else the subject allows only to use a few low-level functions and a few POSIX system calls.

Allowed functions: 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

Features

Basics:

• History of previous entered commands
• Search and launch the right executable (based on the PATH variable, using a relative or an absolute path)
• Environment variables ($ followed by a sequence of characters) expand to their values
• Wildcards * in the current working directory
• ctrl-C, ctrl-D and ctrl-\ behave like in bash
• ’ (single quotes - prevent from interpreting meta-characters in quoted sequence)
• " (double quotes - prevent from interpreting meta-characters in quoted sequence except for $)
• $? expands to the last exit status
• | connect cmds or groups with pipes; output of a cmd is connected to the input of the next cmd via a pipe
• && and || with parenthesis for priorities

Builtins:

• echo with option -n
• cd (relative or absolute path, - for OLDPWD, without arg for HOME)
• pwd without options
• export without options
• unset without options
• env without options
• exit [exit_status] without options

Redirections:

[n] (optional) specifies the file descriptor, if not specified it is stdout/stdin

• [n]< file Redirecting Input
• [n]<< limiter Here Documents
• [n]> file Redirecting Output
• [n]>> file Appending Redirected Output

How to use

The current version of minishell is developed and tested on macOS, but it should work on all UNIX/LINUX based systems as well.

Requirements:

• GCC / CLANG Compiler
• GNU Make
• GNU Readline library

git clone https://github.com/tjensen42/42-minishell.git minishell

cd minishell && make release

./minishell

Dependencies

Install readline with brew

brew install readline

brew link --force readline

Add the path to the lib

Replace ~/.zshrc with ~/.bashrc if you use bash instead of zsh

echo 'export C_INCLUDE_PATH="/usr/local/opt/readline/include:$C_INCLUDE_PATH"' >> ~/.zshrc

echo 'export LIBRARY_PATH="/usr/local/opt/readline/lib:$LIBRARY_PATH"' >> ~/.zshrc

source ~/.zshrc

Install readline on 42 Macs

Install Brew, only if it is not already installed:

rm -rf $HOME/.brew && git clone --depth=1 https://github.com/Homebrew/brew $HOME/.brew && echo 'export PATH=$HOME/.brew/bin:$PATH' >> $HOME/.zshrc && source $HOME/.zshrc && brew update

Install Readline library:

brew install readline

brew link --force readline

echo 'export C_INCLUDE_PATH="$HOME/.brew/include:$C_INCLUDE_PATH"' >> ~/.zshrc

echo 'export LIBRARY_PATH="$HOME/.brew/lib:$LIBRARY_PATH"' >> ~/.zshrc

source ~/.zshrc

Run tests

To check if your minishell build was succesful you can run a tester, which compares most of the features with your current Bash installation. The test compares the stdout and the exit-code directly and checks in case of an error if both print something in stderr.

make test

Activate debug mode

Enter minishell and export the DEBUG env:

export DEBUG=printer

For all next commands you will execute in the minishell you will see the different processing steps from the lexer and parser with syntax highlighting.

Change the command line prompt

1. Enter the SHELL

./minishell

2. Export the PS1 env (also works in Bash and other similar shells)

export PS1='enter your prompt wish...$ '

---

*All 42 projects must be written in C (later C++) in accordance to the 42 School Norm.

Sample restrictions:

• All variables have to be declared and aligned at the top of each function
• Each function can not have more then 25 lines
• Projects should be created with allowed std functions otherwise it is cheating