This is based on the "Build Your Own Shell" Challenge.
This implementation provides an interactive POSIX-style shell that interprets commands, runs external programs and builtins, and exposes a REPL.
It implements a prompt and parsing, with builtins such as exit, echo, and type, and runs executables found in PATH.
Navigation: with pwd and cd(absolute, relative, and home-directory paths) commands.
Quoting: handle single quotes, double quotes, and backslash escaping.
Redirection: redirect stdout and stderr, with options to create or append files.
Background jobs: start jobs with &, list running jobs, and reap finished jobs.
Pipelines: pipe a command’s stdout to the next command’s stdin and chain multiple commands in a single pipeline.