Question

I’m looking for the equivalent of a urlencode for terminal output — I need to make sure that garbage characters I (may) print from an external source don’t end up doing funky things to my terminal, so a prepackaged function to escape special character sequences would be ideal.

I’m working in Python, but anything I can readily translate works too. TIA!

Answer 1

 $ ./command | cat -v  $ cat --help | grep nonprinting -v, --show-nonprinting   use ^ and M- notation, except for LFD and TAB 

Here’s the same in py3k based on android/cat.c:

#!/usr/bin/env python3 '''Emulate `cat -v` behaviour.  use ^ and M- notation, except for LFD and TAB  NOTE: python exits on ^Z in stdin on Windows NOTE: newlines handling skewed towards interactive terminal.        Particularly, applying the conversion twice might *not* be a no-op ''' import fileinput, sys  def escape(bytes):     for b in bytes:         assert 0 <= b < 0x100          if  b in (0x09, 0x0a): # '\t\n'              yield b             continue          if  b > 0x7f: # not ascii             yield 0x4d # 'M'             yield 0x2d # '-'             b &= 0x7f          if  b < 0x20: # control char             yield 0x5e # '^'             b |= 0x40         elif  b == 0x7f:             yield 0x5e # '^'             yield 0x3f # '?'             continue          yield b  if __name__ == '__main__':     write_bytes = sys.stdout.buffer.write      for bytes in fileinput.input(mode='rb'):         write_bytes(escape(bytes)) 

Example:

 $ perl -e'print map chr,0..0xff' > bytes.bin  $ cat -v bytes.bin  > cat-v.out  $ python30 cat-v.py bytes.bin > python.out $ diff -s cat-v.out python.out  

It prints:

 Files cat-v.out and python.out are identical