per freebsd bug report:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=201650
echo "1234 1234 1234" | grep -o ^....
1234
Index: util.c
===================================================================
RCS file: /cvs/src/usr.bin/grep/util.c,v
retrieving revision 1.55
diff -u -p -r1.55 util.c
--- util.c 4 Apr 2016 05:49:47 -0000 1.55
+++ util.c 24 Aug 2016 19:11:01 -0000
@@ -49,7 +49,7 @@
static int linesqueued;
static int procline(str_t *l, int);
-static int grep_search(fastgrep_t *, char *, size_t, regmatch_t *pmatch);
+static int grep_search(fastgrep_t *, char *, size_t, regmatch_t *pmatch,
int);
#ifndef SMALL
static bool grep_cmp(const char *, const char *, size_t);
static void grep_revstr(unsigned char *, int);
@@ -192,14 +192,20 @@ procline(str_t *l, int nottext)
offset = 0;
redo:
if (fg_pattern[i].pattern) {
+ int flags = 0;
+ if (offset)
+ flags |= REG_NOTBOL;
r = grep_search(&fg_pattern[i], l->dat + offset,
- l->len - offset, &pmatch);
+ l->len - offset, &pmatch, flags);
pmatch.rm_so += offset;
pmatch.rm_eo += offset;
} else {
+ int flags = eflags;
+ if (offset)
+ flags |= REG_NOTBOL;
pmatch.rm_so = offset;
pmatch.rm_eo = l->len;
- r = regexec(&r_pattern[i], l->dat, 1, &pmatch, eflags);
+ r = regexec(&r_pattern[i], l->dat, 1, &pmatch, flags);
}
if (r == 0 && xflag) {
if (pmatch.rm_so != 0 || pmatch.rm_eo != l->len)
@@ -459,7 +465,8 @@ nonspecial:
e > s && isword(d[s]) && isword(d[e-1]))
static int
-grep_search(fastgrep_t *fg, char *data, size_t dataLen, regmatch_t *pmatch)
+grep_search(fastgrep_t *fg, char *data, size_t dataLen, regmatch_t *pmatch,
+ int flags)
{
#ifdef SMALL
return 0;
@@ -476,6 +483,8 @@ grep_search(fastgrep_t *fg, char *data,
/* Only try once at the beginning or ending of the line. */
if (fg->bol || fg->eol) {
+ if (fg->bol && (flags & REG_NOTBOL))
+ return 0;
/* Simple text comparison. */
/* Verify data is >= pattern length before searching on it. */
if (dataLen >= fg->patternLen) {
