Slow is a simple program that reduces the output speed of programs on the terminal. The goal is to give the feeling of an old modem connection.

The default output speed is 300bps (bits per second) but you can change it using the -b or --bps parameter with either a numeric value or historical modem presets.

• Historical Modem Presets: Use classic modem speeds like acoustic, dialup, 1200, 2400, etc.
• Accurate Timing: Improved calculation for precise bit-per-second simulation
• Better Error Handling: Graceful shutdown with Ctrl+C and comprehensive error messages
• Verbose Mode: Display timing statistics and processing information
• UTF-8 Compatible: Handles Unicode characters properly
• Standard C Implementation: Uses only standard C library with no external dependencies

Decreases the output speed of the ls -al command to 300bps.

ls -al | slow

Decreases the output speed using a classic 1200 bps modem preset.

cat asciiart.txt | slow -b 1200

Print file at dialup speed (56k) with statistics.

slow -f asciiart.txt -b dialup -v

Use acoustic coupler preset (300 bps).

echo "Hello from 1970s!" | slow -b acoustic

Show help with all available presets.

slow -h

Decreases the output speed of the ls -al command to 300bps.

ls -al | slow

Decreases the output speed using a classic 1200 bps modem preset.

cat asciiart.txt | slow -bps 1200

Print file at dialup speed (56k) with statistics.

slow -f asciiart.txt -bps dialup -verbose

Use acoustic coupler preset (300 bps).

echo "Hello from 1970s!" | slow -bps acoustic

Show help with all available presets.

slow -help

git clone <repository>
cd slow
make

If you have cross-compilation tools installed:

make build

This will attempt to build for both the current platform and Linux amd64.

• GCC compiler with C99 support
• POSIX-compatible system (macOS, Linux, Unix)
• No external dependencies - uses only standard C library

This program uses only the C standard library - no external dependencies required!

If you encounter compilation errors:

# On macOS, ensure Xcode command line tools are installed:
xcode-select --install

# On Linux, ensure GCC is installed:
sudo apt-get install gcc  # Ubuntu/Debian
sudo yum install gcc      # CentOS/RHEL

If characters appear garbled, ensure your terminal supports UTF-8:

export LC_ALL=en_US.UTF-8

If you cannot execute the binary:

chmod +x slow

The slow is compatible with UTF-8, and the difference in the size of the symbols is purposely not taken into account. Instead, we simulate what it would be like if the output via code page with each character occupying only 1 byte.