minishell is a 42 project: You must recreate a minimal version of bash.

• 101/100 ✅

• Pipe (|)
• Environment variables
• Variable expansion
• Redirection (<, <<, >, >>)
• Built-in (echo, pwd, export, unset, env, exit)
• Signal (ctrl+C, ctrl+D, ctrl+\)
• History

Parsing is the most complex part of Minishell.

We start by retrieving the user’s input with readline. Then we verify that all quotes are properly closed, and perform a pre-tokenization step using three token types: [TEXT, REDIRECTION, PIPE]. From there, we apply a few simple syntax rules:

• * ← REDIRECTION → TEXT
• * ← TEXT → *
• !START ← PIPE → REDIRECTION, TEXT

Once the syntax is validated, we proceed with the final tokenization using these types: [CMD, PIPE, IN_FILE, IN_HERE_DOC, OUT_FILE, OUT_FILE_APPEND]. We then join arguments, because two commands cannot appear consecutively without being separated by a pipe.

Next comes the most challenging part: expansion. You need to avoid expanding values that have already been expanded, while also removing quotes at the right moment.

Finally, we transform everything into a set of processes ready for execution.

Illustration