Summary

• Tool under test: uu-nl (uutils coreutils) 0.3.0 @ 514291d
• Reference: GNU nl 9.4
• Impact: uu-nl exits with status 1 and prints an error when -b is provided multiple times (e.g. -ba -bt), while GNU nl treats the later flag as overriding the earlier one and succeeds.
• Reproducer (no input files needed):

  printf 'one\ntwo\n' | /usr/local/bin/uu-nl -ba -bt

  (built inside fuzz-utils:latest, Ubuntu 24.04 base)

Expected Result (GNU nl)

$ printf 'one\ntwo\n' | /usr/bin/nl -ba -bt
     1  one
     2  two
$ echo $?
0

Actual Result (uu-nl)

$ printf 'one\ntwo\n' | /usr/local/bin/uu-nl -ba -bt
error: the argument '--body-numbering <STYLE>' cannot be used multiple times

$ echo $?
1