C Shell

POSIX-compliant command-line shell written in C with custom autocompletion, history navigation, pipelines and I/O redirection.

GNU Readline is used for hooks but and line buffering, but the functionality is all custom.

Features

• Custom autocompletion using prefix trees for:
  • Built-ins (type, echo, exit, pwd, history, cd)
  • Executables in $PATH
  • File paths (including current directory)
  • Displays possible matches and completes longest-common-prefix
• Command history stored in doubly-linked list, with:
  • Up/down arrow navigation
  • history <n> to list the last n entries
• Pipelines (cmd1 | cmd2 | …) and output redirection (>, >>, 2>, etc.)
• Builtin commands: exit, cd, pwd, echo, history, type
• Excutable Files: git, gdb, etc.

Repository

.
├── build.sh
├── main.c # shell loop, parsing, dispatch
├── prefixTree.c # trie implementation for autocomplete
├── prefixTree.h
├── autocomplete.c # readline integration & completion logic
├── autocomplete.h
├── historyList.c - doubly linked list storage
├── historyList.h
├── history.c # readline key bindings & history commands
├── history.h
├── readline_init.c # readline initialization hooks
└── readline_init.h

Requirements

• Libraries: GNU Readline, ncurses (for <curses.h>)
• WSL2 or Linux

How to build and run

chmod +x build.sh
./build.sh
./shell

Todo

• Refresh autocomplete trie when $PATH is modified (e.g. after export)
• Add job‐control (jobs, fg, bg)
• Handle signals properly (e.g. SIGINT, SIGTSTP)
• Swap raw printf calls for Readline buffer APIs