Minishell

Project description

---

Minishell is a 42 project that aims to make us understand how the actual shell process command. The final goal is to have a working shell with basic functionalities.

Features

---

• Prompt : The program must display a prompt while waiting for new command
• History : A working command history
• Redirections : Should handle basic redirection
  • < : should redirect input.
  • > : should redirect output.
  • << : should be given a delimiter, then read the input until a line containing the delimiter is seen. However, it doesn't have to update the history!
  • >> : should redirect output in append mode.
• Pipe : simple pipe (|) should connect two command
• Environment variables : should expand to their value if not into simple quote
• $? : should expand to the exit status
• Signals (in interactive mode)
  • ctrl + c : displays a new prompt on a new line
  • ctrl + d : exits the shell
  • *ctrl + * : does nothing
• Builtins
  • 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 with no options

Parsing

---

The first part of the parsing is the tokenisation. Basically it's the division of the user input into small meaningful piece. That includes :

• redirection (<, >, >>)
• here_doc (<<)
• pipe (|)
• words (all other)

How it work :

1. First we need to expand the environment variables keeping in mind the rules about single and double quote.
2. Then the input is traversed character by character to separate meaningful component wisely, not just splitting on space but group together related pieces. (think about space in quote, missing space between command and pipe or redirection that bash handle well…)
3. Finally we classify the token and assign type to it (REDIRECTION, HERE_DOC…)

Execution