Custom C-Shell - Stardance

Ship #1 Pending review

@jayanth_raveendra on Custom C-Shell · about 7 hours ago

After 11+ hours of wrestling with C, pointers, and POSIX syscalls, I am shipping my custom Unix shell!

What started as a custom lexer and parser (built entirely from scratch without tools like Yacc) has grown into a fully functional execution environment.

Highlights:

Full Execution Engine: Handles complex pipelines (cmd1 | cmd2 | cmd3) and I/O redirection (<, >, >>) using precise file descriptor management (dup2, pipe, fork).

Zoxide-style Navigation: My hop built-in tracks every directory you visit and uses a time-decaying frecency algorithm so you can jump anywhere using just a substring.

Memory Optimization: Built-ins like peek read files backward chunk-by-chunk using lseek to avoid loading massive files into memory.

Building a shell from the ground up completely changed how I look at the terminal. Source code is linked below, as well as a short demo video!

2 devlogs
12h

Try project → See source code →

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@jayanth_raveendra on Custom C-Shell · about 7 hours ago

3h 18m 19s logged

Spent the last 3 hours building the core execution engine for my C-Shell. I implemented external command execution by scanning $PATH and using the fork() and execv() syscalls. The biggest challenge was getting I/O redirection and piping to work correctly. I used dup2() to hijack standard input/output and route them through anonymous temporary files (tmpfile()) to handle multiple file redirections at once.I also ran into a brutal segmentation fault because my built-in commands weren’t expecting redirection operator tokens. I ended up doing a massive architectural refactor to move the entire file descriptor routing to the parent shell level. Now, whether it’s an external binary like ls or my custom peek built-in, they both seamlessly read and write through pipes and files!

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@jayanth_raveendra on Custom C-Shell · 2 days ago

8h 23m 23s logged

I spent the last 8+ hours building a custom POSIX-compliant C shell from scratch. I built a custom lexer and parser to handle right-linear grammar, quoting, and escaping without using standard parsing tools like Lex/Yacc. I also implemented several complex built-in commands natively without relying on exec system calls, including a custom directory jumper (hop) with a time-decaying frecency algorithm (similar to Zoxide) that persists across sessions, and a custom cat-like tool (peek) that uses lseek to read files in reverse chunk-by-chunk to save memory.