Jtdcftul

If I try to search within certain man pages using grep, I get several 'grotty' messages.

For example:

man mpv | grep dvdnav

results in:

mpv dvdnav://[longest|menu|title][/device] [options]

grotty:<standard input> (<standard input>):90690: character above first line discarded

grotty:<standard input> (<standard input>):90694: character above first line discarded

grotty:<standard input> (<standard input>):90698: character above first line discarded

grotty:<standard input> (<standard input>):90702: character above first line discarded

grotty:<standard input> (<standard input>):91895: character above first line discarded

grotty:<standard input> (<standard input>):91899: character above first line discarded

grotty:<standard input> (<standard input>):91903: character above first line discarded

grotty:<standard input> (<standard input>):91907: character above first line discarded

grotty:<standard input> (<standard input>):94450: character above first line discarded

grotty:<standard input> (<standard input>):94454: character above first line discarded

grotty:<standard input> (<standard input>):94458: character above first line discarded

                                                  │dvdnav://              │ dvdnav://menu                         │

What causes these messages and how do I prevent them?

I have no mpv installed, but this seems more a warning of grotty (the program that process man page sources to print it to standard output) probably coming from no-compliant man pages. Have you tried

man mpv 2> /dev/null | grep dvdnav

? This will redirect error and warnings from grotty to the sink, so that you should have a cleaner output.

Nevertheless, that error is probably a bug in the mpv man page (or in grotty, you never know).

I'm pretty sure this is being caused by a bug in the man page text formatter.

man grotty says,

grotty translates the output of GNU troff into a form suitable for
typewriter-like devices.

To debug this first, check if you can also display this man page with groffer (graphical roffer).

When I ran into these errors, I found that groffer worked fine, without the error, but grotty threw up this 'character above first line discarded' error.

So I dug a little deeper. The page that was giving me the trouble was zoneminder.1.

First I unzipped it:

gunzip -k zoneminder.1.gz

Then using this I can run a test:

man -l man.1 | grep jksffjsd   #-l means man the local file, i.e. produce error messages

Now edit zoneminder.1 with divide and conquer. First deleted the last 1/2 of it and the error went away. Then deleted only the last 3/4 of it and the error was still there. Then deleted the last 5/8 of it and the error was still there. Then took a look at it and started to just remove a few lines at a time until the error toggled from on to off.

I found myself in a table, and could only delete some whole entries from the table (see image below).

What I found was that this table was what was messing up, but only when it overflowed to the next page, as is shown here:

Remove one more entry from the table and the errors go away.

So it's fair to just ignore this.

I'll see if I can report it as a bug in grotty.