Vish

This project aims to create a POSIX-compliant shell, following the specification outlined in:
POSIX Shell and Utilities Specification

Overview

Vish currently supports:

• Command execution (spawning child processes)
• Basic built-in utilities (exec, exit, echo, false, true)
• Prompt customization via $PS1
• Line editing improvements (Ctrl+A, Ctrl+E, Ctrl+D)
• Simple parameter expansion ($VAR but not ${VAR:-default} yet)

Work in Progress

• Control flow syntax (e.g., if, while, for)
• Full expansion support (handling quotes, arithmetic, command substitution, etc.)
• More built-in utilities (see the checklists below)
• Job control (bg, fg, jobs, kill, wait, etc.)
• Pipelines (cmd1 | cmd2 | cmd3)
• Command lists (cmd1 && cmd2, cmd1 || cmd2, cmd1; cmd2)
• Compound commands ({ cmd1; cmd2; }, ( cmd1; cmd2 ))
• Function definitions (foo() { echo "Hello"; })
• Signal handling (trap, handling SIGINT, SIGTERM, etc.)
• Pattern matching (globbing: *.txt, file_[0-9].log)

This now covers all major shell features that need to be implemented. Would you like any refinements or additions?

Implementation Details

Command execution follows the correct order as specified in:
POSIX Shell Execution Order

Unspecified utilities may or may not be implemented.

Special Built-In Utilities

• break
• colon
• continue
• dot
• eval
• exec
• exit
• export
• readonly
• return
• set
• shift
• times
• trap
• unset

Built-In Utilities

• alias
• bg
• cd
• command
• echo
• false
• fc
• fg
• getopts
• hash
• jobs
• kill
• printf
• pwd
• read
• test
• true
• type
• ulimit
• umask
• unalias
• wait