undocumented nl behavior with -bt

[paul]

re:  nl (GNU coreutils) 6.9  Fedora 7 Linux

Good morning--

I have not used nl for a long time but just found a use for it.  It does the 
numbering that I want but it does more than that.  The file I am numbering is 
many lines of text with interspersed blank lines.  (It is data exported from 
an accounting system that is input to a perl program.)  The blank lines would 
be more accurately be called empty or null lines as they do not contain any 
white space characters, simply consecutive new line characters in the data 
file.  The perl program recognizes these empty lines and handles them as 
required by its specifications.

After numbering the lines using:  nl  -s, -w1 -nln oldfile > newfile
the perl program now chokes on the once empty lines in newfile.  Upon 
examination I find that the empty lines are no longer empty.  They now 
contain a number of space characters equal to the setting of the -w option.  
They cannot be suppressed entirely by specifying -w0 as that is reported as 
an invalid value, which is reasonable considering the purpose of -w.

The man page (and info page) states that the t style is to "number only 
nonempty lines".  This it does but it also changes the nonempty lines into 
lines containing spaces.  I feel that this latter behavior should not be 
included in nl.

Since nl has been around for many years there may be some users taking 
advantage of this undocumented behavior.  Therefore I propose that an option 
be added to allow the user to suppress this historical behavior.  In other 
words the option would direct nl to leave empty lines empty.  I suggest the 
option be "-e".  An alternative would be to specify this with a new body 
numbering style instead of an option.

Thank you for your consideration of this matter.

paul

ps--Mac OS X version of nl has the same behavior and worse.  If the -s option 
is present it inserts the separator character into the empty line following 
the string of spaces.  I have no other Unix platforms available on which to 
try nl.

-- 
Paul Almquist
Eau Claire, WI  USA
address@hidden