clout

clout is a small Unix utility that colorizes the standard output and standard error streams of a command independently.

It executes a command, captures its standard output and standard error through separate pipes, and writes each stream using a configurable ANSI color. By default, stdout is green and stderr is red.

The project is written in C and uses fundamental Unix process and I/O interfaces, including fork(2), execvp(3), pipe(2), dup2(2), and poll(2).

Features

• Execute commands using execvp(3).
• Capture stdout and stderr through separate pipes.
• Colorize stdout and stderr independently.
• Select the stdout color with -o.
• Select the stderr color with -e.
• Read both output streams using poll(2).
• Handle nonblocking pipe I/O.
• Propagate the command's exit status.
• Report 128 + signal number when the command terminates due to a signal.
• Provide a built-in usage message with -h.
• Include a manual page.

Usage

clout [-h] [-e color] [-o color] command [argument ...]

The default colors are:

• stdout: green
• stderr: red

Examples

Run a command with the default colors:

clout ls /

Set the stdout color:

clout -o cyan ls /

Set the stderr color:

clout -e yellow sh -c 'echo "error" >&2'

Configure both streams independently:

clout -o green -e red sh -c 'echo "output"; echo "error" >&2'

Display usage information:

clout -h

Colors

The following colors are supported:

• black
• red
• green
• yellow
• blue
• purple
• cyan
• white
• gray
• bright-red
• bright-green
• bright-yellow
• bright-blue
• bright-purple
• bright-cyan
• bright-white

Building

clout uses a standard Makefile and does not require an external build system.

Build:

make

Clean build artifacts:

make clean

Documentation

The manual page is available as clout(1).

Read it directly from the source tree:

man ./clout.1

Render it with mandoc:

mandoc clout.1

Check the manual page for errors:

mandoc -T lint clout.1

License

Copyright (C) 2026 Mahdi Feyzolahy

License: BSD-2-Clause

See the LICENSE file for the full license text.