Understanding a patch file [OT?]

[Leonidas Tsampros]

On Fri, Nov 11, 2005 at 10:53:38PM +0200, Leonidas Tsampros wrote:
> On Fri, Nov 11, 2005 at 01:16:15PM -0500, Steve Bertrand wrote:
> > Hi everyone...
> > 
> > This may be off-topic, but I know someone may be able to help. I am
> > trying to better understand how to use diff, and moreso, understand it's
> > output.
> > 
> > In particular, I can't quite grasp exactly what the identifiers in
> > between @@ and @@ represent exactly. Here is a patch file I created. The
> > first change looks like it will replace lines 1 through 5, but then I
> > look at the second change, and it completely confuses me (-11,6 +11,8).
> > Can someone please clarify why 11 and 8?
> > 
> 
> I think this kind of diff output is called "unified". It displays
> "hunks" of differences while each hunk shows one aera where the file
> differs. 
> 
> > --- randbak.pl  Wed Oct 12 17:27:10 2005
> > +++ randbak2.pl Fri Nov 11 13:06:51 2005
> 
> According to "info diff", the file displayed here is the file
> modification time.

Correcting what i just wrote : According to "info diff", the *time*
displayed here is the file's modification time.

> > @@ -1,5 +1,5 @@
> >  #!/usr/bin/perl
> > -
> > +#
> >  use warnings;
> >  use strict;
> >  use Storable;
> 
> This is the first hunk of changes between the files. The number -1,5
> is the line range in the first file while +1,5 is the file range on
> the second file . But 1,5 doesn't mean all lines between line 1 and
> line 5. It means in line 1 ,  + 5 lines afterward. (consider 5 as the
> length of the compared regions)
> 
> In this hunk you can see clearly that you removed a whiteline and you
> add a comment line, so the total numbers of line in both files are
> exactly the same. Thus you've got -1,5 +1,5. The length of the
> compared region in boths files did not change.
> 
> If the second number is different, like in the following hunk, then
> the data displayed are lines 11-16 on the first file (-11,6) and
> because you added two lines (the ones starting with +) the file range
> of the compared region in the second file is 11-18 (+11,8)
> 
> 
> I hope this helps and i'm terribly sorry for my english. Alternatively
> you can check `info diff' for more information on diff different kinds
> of output.
> 
> > @@ -11,6 +11,8 @@
> >  my $num;
> >  my $sum = "sum";
> >  my $total = 0;
> > +
> > +# Test
> > 
> >  if (-e "randomcount"){
> >         $href = retrieve ("randomcount");
> > 
> > 
> > Thank you for any advice!
> > Steve
> > 
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