l command uses different escape format than GNU

[sylvestre]

Rust (incorrect format)

  $ echo "cÃ🧰y" | cargo run --quiet -- -e 'l'
  # Output: c\u00C3\U0001F9F0y$
  # (Uses \uXXXX and \UXXXXXXXX Unicode escape format)
  # Exit code: 0

GNU (correct format)

  $ echo "cÃ🧰y" | /usr/bin/sed -e 'l'
  # Output: c\303\203\360\237\247\260y$
  # (Uses \XXX octal escape format)
  # Exit code: 0

Bug Found by Fuzzer

[e-kwsm]

https://pubs.opengroup.org/onlinepubs/9799919799/utilities/sed.html

The characters listed in XBD Escape Sequences and Associated Actions ('\', '\a', '\b', '\f', '\r', '\t', '\v') shall be written as the corresponding escape sequence; the '\n' in that table is not applicable. Non-printable characters not in that table shall be written as one three-digit octal number (with a preceding <backslash>) for each byte in the character (most significant byte first).

BSD thinks à and 🧰 are printable under UTF-8:

sed	LANG	output
GNU	C	c\303\203\360\237\247\260y$
GNU	en_US.UTF-8	c\303\203\360\237\247\260y$
BSD	C	c\303\203\360\237\247\260y$
BSD	en_US.UTF-8	cÃ🧰y$
uutils	C	c\u00C3\U0001F9F0y$
uutils	en_US.UTF-8	c\u00C3\U0001F9F0y$

But anyway Unicode escaped string is not compliant with POSIX.