flop

Flip output is an interactive command-line tool that helps you manage output statements in C/C++/Rust/Java code. It works by recursively searching your codebase and lets you toggle statements with an intuitive interface.

Features

• Interactive by default - Beautiful TUI for selecting specific statements with file navigation
• Fast and recursive - Processes entire directory trees including subdirectories
• Flexible filtering - Detects all output functions by default, or use --debug to filter by keyword
• Preview mode - Preview changes without modifying files with --preview
• Safe and reversible - Disable output for production (on), enable for debugging (off)
• Smart detection - Automatically detects printf-family functions, C++ streams, Rust macros, and Java output statements
• Syntax highlighting - Color-coded output similar to ripgrep for easy reading
• Multiple modes - Comment out, uncomment, or permanently delete statements

Quick example

# Disable all output (interactive TUI by default)
$ flop on

# Disable only debug output (interactive)
$ flop on --debug

# Disable all output in batch mode (with confirmation)
$ flop on --yes

# Preview what would be changed without modifying files
$ flop on --preview src/

# Disable debug output only in batch mode
$ flop on -dy src/

# Delete all output statements permanently (interactive)
$ flop delete src/

# Process a single file
$ flop on main.c

Installation

From crates.io

If you're a Rust programmer, flop can be installed with cargo:

cargo install flop-cli

From source

You'll need Rust installed (1.70.0 or newer).

git clone https://github.com/Justhiro55/flop.git
cd flop
cargo build --release

The binary will be available at ./target/release/flop.

Install to system

cargo install --path .
# Or copy the binary manually
sudo cp target/release/flop /usr/local/bin/

Usage

flop <COMMAND> [OPTIONS] [PATH]

Commands:
  off      Uncomment output statements (enable output)
  on       Comment out output statements (disable output)
  delete   Delete output statements permanently

Arguments:
  [PATH]  Path to file or directory (defaults to current directory if not specified)

Options:
  -d, --debug    Only process output statements containing 'debug' keyword
  -y, --yes      Skip interactive selection (batch mode, confirmation still required)
  -p, --preview  Preview mode - show what would be changed without modifying files
  -h, --help     Print help

How it works

By default, flop searches for all C/C++/Rust/Java output functions in your codebase. Use the --debug flag to filter only statements containing "debug" or "DEBUG" keywords.

Detected output functions include:

• C standard I/O functions (printf family, puts family, write, perror)
• C++ stream operators (std::cout, std::cerr, std::clog)
• Rust macros (println!, eprintln!, dbg!, etc.)
• Java output statements (System.out, System.err)

Supported file extensions:

• .c
• .h
• .cpp
• .hpp
• .cc
• .cxx
• .rs
• .java

Detected functions:

C standard functions:

• printf(), fprintf(), sprintf(), snprintf(), dprintf()
• puts(), fputs()
• write()
• perror()
• printf_debug()

C++ streams:

• std::cout
• std::cerr
• std::clog

Rust macros:

• println!(), eprintln!()
• print!(), eprint!()
• dbg!()

Java statements:

• System.out.println(), System.out.printf(), System.out.print()
• System.err.println(), System.err.printf(), System.err.print()

Examples

Interactive mode (default)

By default, flop opens an interactive TUI where you can select which statements to process:

# Disable all output statements (interactive)
flop on

# Navigate with arrow keys or hjkl
# Toggle selection with Space/Tab
# Navigate between files with Left/Right arrows
# Press Enter to confirm, Esc/q to cancel

Disable output in current directory

# Interactively disable all output
flop on

# Disable only debug output (interactive)
flop on --debug

Enable output in a specific directory

# Interactively enable all output
flop off src/

# Enable only debug output (interactive)
flop off --debug src/

Batch mode with --yes flag

Use -y or --yes to skip interactive selection and process all matched statements (confirmation still required):

# Disable all output in batch mode
flop on --yes

# Disable debug output only in batch mode
flop on -dy src/

# Enable all output in batch mode
flop off -y

Process a single file

# Interactive mode
flop on main.c

# Batch mode
flop on -y main.c

Delete statements permanently

# Interactive deletion
flop delete src/

# Batch deletion (confirmation required)
flop delete -y src/

Warning: This permanently removes statement lines from your files. Use with caution!

Preview mode with --preview flag

Preview what would be changed without actually modifying any files:

# Preview changes (interactive)
flop on --preview src/

# Preview in batch mode
flop on -yp src/

# Preview debug output only
flop on -dp src/

Preview mode never modifies files. It's useful for:

• Checking what statements will be affected before committing
• Verifying detection patterns
• Safely exploring the tool's behavior

Filter debug output with --debug flag

By default, flop detects all output functions. Use --debug to filter only statements containing "debug" or "DEBUG" keywords:

# Process only debug output (interactive)
flop on --debug

# This will detect:
# - printf("debug: message") ← detected
# - printf("Regular message") ← NOT detected with --debug
# - std::cout << "DEBUG: xyz" ← detected

Cancel operation

When prompted for confirmation, type n to cancel without making changes:

Do you want to disable (comment out) these statements? (y/n): n
Operation cancelled.

Building

cargo build --release

Testing

The repository includes sample C files in the tests/ and sample/ directories for testing:

# Build the project
cargo build --release

# Navigate to the tests directory and run flop without path argument
cd tests/
../target/release/flop on

# Disable all debug statements (type 'y' to confirm)
../target/release/flop on

# Verify they are commented out
cat main.c

# Enable all debug statements (type 'y' to confirm)
../target/release/flop off

# Verify they are uncommented
cat main.c

# Go back to project root
cd ..

You can also test with the sample/ directory which contains more comprehensive examples:

./target/release/flop on sample/

Why use flop?

• Speed up your workflow - No need to manually toggle output statements
• Interactive by default - Beautiful TUI with file navigation makes selection intuitive
• Avoid mistakes - Preview mode and confirmation prompts prevent accidental changes
• Clean commits - Easily disable output before committing (flop on)
• Quick debugging - Enable output when investigating issues (flop off)
• Production cleanup - Permanently delete statements with the delete command
• Safe exploration - Use --preview to preview changes before applying them
• Flexible filtering - Process all output or filter by debug keyword with --debug
• Batch automation - Use --yes flag for scripts while keeping confirmation

Why not use flop?

• Language specific - Only works with C/C++/Rust/Java code
• Simple pattern matching - May not catch all debug logging patterns
• Standard output only - Doesn't work with logging libraries (log4c, spdlog, log crate, Log4j, SLF4J, etc.)

License

This project is dual-licensed under the MIT License and Apache License 2.0.

See LICENSE for details.