xargs exits on empty line from stdin

[mknos]

• BSD versions of xargs don't support the -l option
• Standards document for xargs mentions -L but not -l [1]
• Follow GNU version and accept -l as an alias for -L, but list standard -L in usage string
• Behaviour of -L/-l didn't match xargs on my linux system: input loop was terminated on first empty line of STDIN
• Skipping empty lines makes the behaviour match GNU version (empty means the line contains no non-spaces)

1. https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/utilities/xargs.html

%cat -n in # not all lines have content
     1	#!/usr/bin/perl
     2	
     3	=begin metadata
     4	
     5	Name: awk
     6	Description: pattern-directed scanning and processing language
     7	Author: Tom Christiansen, tchrist@perl.com
     8	Author: Larry Wall, larry@wall.org
     9	License: perl
    10	

%xargs -L 1 < in # implicit 'echo' for each line of stdin
#!/usr/bin/perl
=begin metadata
Name: awk
Description: pattern-directed scanning and processing language
Author: Tom Christiansen, tchrist@perl.com
Author: Larry Wall, larry@wall.org
License: perl

%perl xargs -L 1 < in # patched version
#!/usr/bin/perl
=begin metadata
Name: awk
Description: pattern-directed scanning and processing language
Author: Tom Christiansen, tchrist@perl.com
Author: Larry Wall, larry@wall.org
License: perl

[briandfoy]

changes: -l is an alias for -L (GNU extension)