Interrupting display of command-line help text

[FrankB]

From what I've read it seems to me this isn't really a surprise since the real cause seems to be a possible bug in Perl itself (and not a bitness mismatch as I thought initially).

Seems logical, and the thought had crossed my mind. But it was bed time by then.

Fixing the problem in Perl itself seems to be the cleanest way, but might take a while.

We could also consider using a tiny wrapper around "more" to catch the negative return value (errorlevel).

Agree. If I can be of help let me know.

[Phil Harvey]

Thanks all.  I'll try wrapping the system "more" call in an eval to see if that helps.

- Phil

[FrankB]

I would be happy to test that Phil.

[Phil Harvey]

I've tested this on my Windows 7 virtual machine and it seems to work.  Replace the last line of code in exiftool.pl with these lines:

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    # trap warnings and run in eval to avoid Perl bug which gives "Can't spawn" warning on ^C
    local $SIG{'__WARN__'} = sub { $evalWarning = $_[0] };
    eval { system(qq{more < "$docFile"}) };
I'm sorry I was so slow about this -- I was thinking it would require a change to the launcher, and didn't realize I could patch it in ExifTool so easily.

- Phil

[FrankB]

I can confirm that this works on Windows 11. Both in Terminal and Conhost.

Side note: if you leave out the < in

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eval { system(qq{more < "$docFile"}) }; (So it is the first parm)

More shows the percentage. (Maybe only on Windows!)

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      GPS            r/w/c  |  AFCP           r/w  |  Picture Info   r
      IPTC           r/w/c  |  Kodak Meta     r/w  |  Adobe APP14    r
      XMP            r/w/c  |  FotoStation    r/w  |  MPF            r
      MakerNotes     r/w/c  |  PhotoMechanic  r/w  |  Stim           r
-- More (4%) --
Frank

[Phil Harvey]

Thanks Frank.

The percent would be useful, but I'll leave it with the "<" to be safe.

- Phil

[stan]

I've tested this on my Windows 7 virtual machine and it seems to work.  Replace the last line of code in exiftool.pl with these lines:

Works quite nicely in Win10 too (naturally)! However, I suggest a slight modification to reintroduce the error message in case windows_exiftool.txt is somehow missing:

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    # !PLEASE WRITE THE ACTUAL IF CONDITION PERL CODE BELOW!

    if($docFile does not exist) {
        print "Error opening doc file $docFile\n";    # similar to earlier "Error opening arg file $argFile\n"
    } else {
        # trap warnings and run in eval to avoid Perl bug which gives "Can't spawn" warning on ^C
        local $SIG{'__WARN__'} = sub { $evalWarning = $_[o] };
        eval { system(qq{more "$docFile"}) };
    }


The percent would be useful, but I'll leave it with the "<" to be safe.

The description of Perl's system() states that if there are no shell metacharacters (such as the redirection operator '<') in the argument, then it is split into words and passed directly to execvp() which is more efficient. So if it doesn't break anything then I agree with Frank that the percentage display thanks to leaving out '<' would be quite useful, and as a bonus possibly more efficient too.

[Phil Harvey]

Hi Stan,

These are reasonable suggestions.  I will look into implementing them after the planned 13.00 production release.  For 13.00 I am only including bug fixes.

- Phil

[stan]

Thanks Phil; makes no difference to me whether the above code makes its way into ExifTool 13.00 or 13.01. Thanks to Frank and Oliver for their valuable inputs too.

[stan]

Hi Phil, just a gentle reminder that an existence check for the help text file is still needed.

[obetz]

Why should this file not exist? There would be more severe consequences with other files, so if we refine your approach, ExifTool should do an integrity check over everything?