Like cat, but highlight invisible characters

0cat

#!/usr/bin/env python3
"""
Like cat, but highlight invisible characters
"""
import argparse
import sys


if sys.stdout.isatty():
    BOLD = "\033[01m"
    RED = "\033[31m"
    GREEN = "\033[32m"
    ORANGE = "\033[33m"
    PURPLE = "\033[35m"
    CYAN = "\033[36m"
    GREY = "\033[37m"
    RESET = "\033[0;0m"
else:
    BOLD = ""
    RED = ""
    GREEN = ""
    ORANGE = ""
    PURPLE = ""
    CYAN = ""
    GREY = ""
    RESET = ""


def show_file(fp):
    while block := fp.read(4096):
        for ch in block:
            if ch == "\0":
                sys.stdout.write(f"{ORANGE}[0]{RESET}")
            elif ch == "\n":
                print(f"{CYAN}\\n{RESET}")
            elif ord(ch) < 32:
                sys.stdout.write(f"{RED}.{RESET}")
            else:
                sys.stdout.write(ch)


def main():
    parser = argparse.ArgumentParser(
        formatter_class=argparse.RawDescriptionHelpFormatter, description=__doc__
    )

    parser.add_argument("file", nargs="*", help="files to show, use stdin if not set")
    args = parser.parse_args()

    if args.file:
        for path in args.file:
            with open(path) as fp:
                show_file(fp)
    else:
        show_file(sys.stdin)

    return 0


if __name__ == "__main__":
    sys.exit(main())
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