minishell

Contents

• Info
• How to use
  • Clone repo and submodules
  • Linux dependencies
  • MAC dependencies
  • Compile and execute
  • Install
• Features
  • Built-in commands
• Aproach
• Shell grammar
• Screenshots

Info

This project aims to recreate most of the bash shell.

• Status: finished
• Result: 125%
• Observations:
  • It is compatible with Linux and Mac OS.
  • It does not use VT100 escape characters.

developed by: izenynn and 0xk0sta

How to use

Clone repo and submodules

git clone --recurse-submodules https://github.com/izenynn/minishell.git

Linux dependencies

Install readline library:

• On Debian based platforms, like Ubuntu:

sudo apt install libreadline-dev

• Platforms with yum, like SUSE:

yum install readline-devel

• For other platform please search for the package name on google, thx :)

MAC dependencies

• Install readline library:

brew install readline

Compile and execute

Run make (make rules: all, clean, fclean and re)

cd ./minishell && make

Execute the ./minishell binary generated after running make

./minishell

Install

To install minishell in your machine and be able to use it in any directory like any other command, run make install (make sure you have the correct access rights).

sudo make install

To change the install directory specify the BIN_DIR variable on make

sudo make install -D 'BIN_DIR=/usr/local/bin'

Features

• Recreates most of the bash shell.
• support for config file .minishrc (like bash .bashrc).
• comments with # (NOTE: # must be at the start of the line).
• Pipes | works like in bash.
• Redirections <, >, <<, >> work like in bash.
• ;, && and || work like in bash.
• Parenthesis: ( and ) works with &&, || and ; for priorities.
• $? works like in bash.
• wildcards * and ? works for the current directory.
• Handle signals: Ctrl-C, Ctrl-D and Ctrl-\ like in bash.
• Enviroments variables.
• Arrow keys.
• History (command history).
• Auto-complete with tab key.

Built-in commands

• echo
• cd
• pwd
• export
• unset
• env
• exit

Aproach

minishell is formed by 3 components:

1. Lexical analyzer: parse the input line into tokens.

2. Parser: parse tokens into an abstract syntax tree (ast).

3. Executor: execute the commands

To see how it works, go to src/main/handle_line.c, uncomment the functions print_ast and print_tokens, in line 18 and 78, add the following lines to the handle_line function and run make again:

 void	handle_line(char *line, t_bool is_alloc)
 {
 	t_lexer	lex;
 	t_ast	*ast;
 	int		ret;

 	ast = NULL;
 	if (check_line(line, is_alloc) == 1)
 		return ;
 	ret = lexer_build(line, ft_strlen(line), &lex);
 	if (ret <= 0)
 	{
 		if (ret == 0 && g_sh.tokdel == FALSE)
 			write(STDERR_FILENO, "error: syntax error\n", 20);
 		free_line(line, is_alloc);
 		lexer_del(&lex);
 		return ;
 	}
 	free_line(line, is_alloc);
+	print_tokens(&lex);
 	if (lex.n_toks == 0 || parse(&lex, &ast))
 	{
 		free_all(&lex, ast);
 		return ;
 	}
+	print_ast(ast, 0); printf("------------------------------------\n");
 	if (exec_heredoc(ast) == 0)
 		exec_ast(ast);
 	free_all(&lex, ast);
 }

Example:

minishell$ "invalid command" || (echo hello && echo world!)
------------------------------------
TOKENS:
n_tok: 10
type: -1, data: invalid command
type: 124, data: |
type: 124, data: |
type: 40, data: (
type: -1, data: echo
type: -1, data: hello
type: 38, data: &
type: 38, data: &
type: -1, data: echo
type: -1, data: world!
type: 41, data: )
type: 0, data:
------------------------------------
AST:

                              type: arg, data: world!

                    type: cmd, data: echo

          type: &&

                              type: arg, data: hello

                    type: cmd, data: echo

type: ||

          type: cmd, data: invalid command
------------------------------------
invalid command: command not found
hello
world!
minishell$

Shell grammar

Grammar

<command line> : <and or> ';' <command line>
               | <and or> ';'
               | <and or>
               ;

<and or>       : <job> '&&' <and or>
               | <job> '||' <and or>
               | <job>
               | '(' <command line> ')' '&&' <and or>
               | '(' <command line> ')' '||' <and or>
               | '(' <command line> ')'
               ;

<job>          : '(' <command> ')' '|' <job>
               |     <command>     '|' <job>
               | '(' <command> ')'
               |     <command>
               ;

<command>      : <token list>
               ;

<token list>   : [name]  <token list>
               | [token] <token list>
               | [redir] <token list>
               | (null)
               ;

<redir>        : <redir in>
               | <redir out>
               ;

<redir in>     : '<<' [file]
               | '<'  [file]
               ;

<redir out>    : '>>' [file]
               | '>'  [file]
               ;

Screenshots