How to Use a Python Script to Highlight Log Keywords in the Terminal

When testing an SDK’s logging, you may want to highlight different log tags in the terminal so that the output is easier to read.

1. Copy the script to your local machine.

2. Edit the script’s config dictionary: the tag is the keyword to highlight and color defines the foreground and background colors (format: foreground;background ).

Example configuration:

config = { 'tag0': '37;42', 'tag1': '37;43', 'tag2': '37;44', }

3. Add an alias to your shell startup file ( .zshrc or .bashrc ).

alias logcolor='python -u /path/to/logcolor.py' alias grep='grep --color --line-buffered'

4. Pipe the standard output of any command into logcolor to see highlighted tags.

Example:

> your_command | logcolor

The full logcolor.py script:

#!/usr/bin/env python # encoding: utf-8 """ Format: \033[display;foreground;backgroundm] Foreground Background Color 30 40 Black 31 41 Red 32 42 Green 33 43 Yellow 34 44 Blue 35 45 Magenta 36 46 Cyan 37 47 White Display Meaning 0 Default 1 Bright 4 Underline 5 Blink 7 Reverse 8 Concealed """ import sys import signal config = { 'tag0': '37;42', 'tag1': '37;43', 'tag2': '37;44', } def color_line(line): for key, value in config.items(): line = line.replace(key, '\033[1;%sm%s\033[0m' % (value, key)) return line def exit_gracefully(signal, frame): sys.exit(0) if __name__ == '__main__': signal.signal(signal.SIGINT, exit_gracefully) for line in iter(sys.stdin.readline, ''): print(color_line(line.rstrip())) sys.stdout.flush()

Tips

1. Use grep --line-buffered to avoid output buffering delays when piping through logcolor .

2. When the command’s output is redirected to stdout, it is line‑buffered by default; otherwise it may be block‑buffered (often 4096 bytes), which can cause noticeable latency.

3. In Python, avoid iterating directly over sys.stdin because it can introduce similar buffering delays; instead use for line in iter(sys.stdin.readline, '') as shown in the script.