On Sun, Jul 17, 2011 at 07:28:11PM +0100, Jason McIntyre wrote:
> On Sun, Jul 17, 2011 at 11:43:03AM -0400, Ted Unangst wrote:
> > I recently learned that our grep does not support the \<\> syntax for
> > word boundaries, only the somewhat more difficult to use [[:<:]] format.
> > It's fairly easy to convert one to the other however.
> >
>
> if you do this, we will need to think carefully about how to document
> it. grep(1) itself does not discuss REs, and instead points to
> re_format(7). but you are proposing an extension to grep only.
>
> can i ask why you want to support this? it is a gnu grep thing or
> something?
\
It is quite a common usage for word boundarys in regular expressions.
As a data point nvi (/usr/bin/vi on openbsd) does support this
shorthand (but only refers to re_format(7) in the manpage, a quick dig
in the source shows it has a conversion function that converts between
``vi'' REs and posix in ex_subst.c (re_conv())). Because of this i find
myself botching grep regexes regularly because it doesn't.
(So that's support for the idea from me, but I won't bitch too loudly if
it is shot down).
-0-
>
> jmc
>
> > Index: grep.c
> > ===================================================================
> > RCS file: /home/tedu/cvs/src/usr.bin/grep/grep.c,v
> > retrieving revision 1.44
> > diff -u -p -r1.44 grep.c
> > --- grep.c 8 Jul 2011 01:20:24 -0000 1.44
> > +++ grep.c 17 Jul 2011 15:38:58 -0000
> > @@ -163,6 +163,54 @@ struct option long_options[] =
> > {NULL, no_argument, NULL, 0}
> > };
> >
> > +#ifndef SMALL
> > +char *
> > +fix_word_boundaries(char *pat)
> > +{
> > + size_t newlen;
> > + int bs, repl;
> > + char c, *newpat, *p, *r;
> > +
> > + repl = 0;
> > + p = pat;
> > + while ((p = strstr(p, "\\<"))) {
> > + p += 2;
> > + repl++;
> > + }
> > + p = pat;
> > + while ((p = strstr(p, "\\>"))) {
> > + p += 2;
> > + repl++;
> > + }
> > + if (!repl)
> > + return pat;
> > + newlen = strlen(pat) + 1 + repl * 5;
> > + newpat = grep_malloc(newlen);
> > + p = pat;
> > + r = newpat;
> > + bs = 0;
> > + while ((c = *p++)) {
> > + if (bs && (c == '<' || c == '>')) {
> > + /* overwrite previous backspace */
> > + snprintf(r-1, 8, "[[:%c:]]", c);
> > + r += 6;
> > + bs = 0;
> > + continue;
> > + } else if (!bs && c == '\\') {
> > + bs = 1;
> > + } else {
> > + bs = 0;
> > + }
> > + *r++ = c;
> > + }
> > + *r = 0;
> > + if (newlen <= strlen(newpat))
> > + abort();
> > + free(pat);
> > + return newpat;
> > +
> > +}
> > +#endif
> >
> > static void
> > add_pattern(char *pat, size_t len)
> > @@ -198,6 +246,12 @@ add_pattern(char *pat, size_t len)
> > pattern[patterns] = grep_malloc(len + 1);
> > memcpy(pattern[patterns], pat, len);
> > pattern[patterns][len] = '\0';
> > +#ifndef SMALL
> > + if (!Fflag) {
> > + pattern[patterns] =
> > fix_word_boundaries(pattern[patterns]);
> > + }
> > +#endif
> > +
> > }
> > ++patterns;
> > }
>
--
HELP! MY TYPEWRITER IS BROKEN!
-- E. E. CUMMINGS
