shell-cpp

A minimal interactive Unix-like shell written in C++23.

It supports:

• interactive prompt (GNU readline)
• command history (saved to a file)
• basic builtins
• running external commands via execvp
• pipelines (cmd1 | cmd2 | ...)
• stdout/stderr redirection (>, >>, 2>, 2>>, 1>, 1>>)
• tab completion for builtins and executables found in $PATH

Repo: https://github.com/UmarlyPoeta/shell-cpp

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Requirements

• Linux / macOS (POSIX: fork, execvp, waitpid, pipe)
• CMake >= 3.13
• A C++ compiler with C++23 support
• readline development package

On Debian/Ubuntu:

sudo apt-get update
sudo apt-get install -y build-essential cmake libreadline-dev

On Fedora:

sudo dnf install -y gcc-c++ cmake readline-devel

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Building

cmake -S . -B build
cmake --build build -j

The binary will be:

• build/shell

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Running

./build/shell

You should see a banner and a prompt:

patryk-shell v0.1 $

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Builtins

Implemented builtins (see src/builtins.cpp):

• echo ... – prints arguments
• pwd – prints current directory
• cd <dir> – changes directory (supports ~ expansion)
• type <cmd> – prints whether command is a builtin or a path-resolved executable
• history – prints history
  • history -r <file> – read history from file
  • history -w <file> – write history to file
  • history -c – clear in-memory history
  • history -a <file> – append new entries since last save
• exit – exits the shell (and saves history)

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Pipelines

Pipelines are supported using |:

ls -la | grep cpp | wc -l

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Redirection

Supported operators:

• > / 1> – redirect stdout (truncate)
• >> / 1>> – redirect stdout (append)
• 2> – redirect stderr (truncate)
• 2>> – redirect stderr (append)

Examples:

echo hello > out.txt
ls does-not-exist 2> err.txt
ls -la >> out.txt

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History file

History is stored in:

• $HISTFILE if set
• otherwise .my_shell_history in the current working directory

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Code structure

Key files:

• src/main.cpp – REPL loop + dispatch (builtins / external / pipelines)
• src/parser.cpp – parsing input / redirections / pipelines
• src/executor.cpp – running external commands and pipelines
• src/builtins.cpp – builtin implementations
• src/completions.cpp – readline completion
• src/utils.cpp – helper functions + banner + history helpers

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Notes / Limitations

This is a learning project and intentionally minimal.

Not implemented (yet):

• job control (fg, bg, signals)
• environment variable expansion ($VAR)
• globbing (*.cpp)
• advanced quoting/escaping edge cases
• background execution (&)

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License

MIT (or specify your preferred license). If you want, add a LICENSE file.