Christopher Zimmermann wrote:
> Hi,
>
> I just tried to find the byte position of a string within a binary file
> using grep. Our base grep -bo let me down because it will only display
> the position of the '\n' delimited line, not the position of the
> pattern.
>
> That's what our grep(1) says:
> -b The offset in bytes of a matched pattern is displayed in
> front of the respective matched line.
>
> what it actually does is displaying the offset of the line, not the
> pattern. I think it should read as following:
>
> -b Each output line is preceded by its position (in bytes) in the
> file. If option -o is also specified, the offset in bytes of
> the actual matched pattern is displayed.
This seems like the right behavior. But the diff can be simpler?
> Index: util.c
> ===================================================================
> RCS file: /cvs/src/usr.bin/grep/util.c,v
> retrieving revision 1.59
> diff -u -p -r1.59 util.c
> --- util.c 23 Jan 2019 23:00:54 -0000 1.59
> +++ util.c 16 Jul 2019 21:16:18 -0000
> @@ -250,9 +250,9 @@ print:
> if (Bflag > 0)
> printqueue();
> linesqueued = 0;
> - printline(l, ':', oflag ? &pmatch : NULL);
> + printline(l, ':', &pmatch);
> } else {
> - printline(l, '-', oflag ? &pmatch : NULL);
> + printline(l, '-', &pmatch);
> tail--;
> }
> }
> @@ -651,12 +651,14 @@ printline(str_t *line, int sep, regmatch
> if (bflag) {
> if (n)
> putchar(sep);
> - printf("%lld", (long long)line->off);
> + printf("%lld",
> + (long long)line->off
> + + (pmatch && oflag ? pmatch->rm_so : 0));
> ++n;
> }
> if (n)
> putchar(sep);
> - if (pmatch)
> + if (oflag && pmatch)
> fwrite(line->dat + pmatch->rm_so,
> pmatch->rm_eo - pmatch->rm_so, 1, stdout);
> else
I don't see why you needed to change this much.
- printf("%lld", (long long)line->off);
+ printf("%lld",
+ (long long)line->off
+ + (pmatch ? pmatch->rm_so : 0));
That should be enough, no?
