this was proposed a while ago, but got sidetracked by some nonstandard option discussion. bringing it back in slightly different form.
-o only prints the matching parts of a line, not the entire line. While this is possible using awk, the same could be said of everything grep does. It is intended to match the behavior of the same option in gnu grep. Index: grep.1 =================================================================== RCS file: /home/tedu/cvs/src/usr.bin/grep/grep.1,v retrieving revision 1.40 diff -u -r1.40 grep.1 --- grep.1 4 Mar 2011 03:11:22 -0000 1.40 +++ grep.1 20 Jun 2011 19:38:55 -0000 @@ -38,7 +38,7 @@ .Sh SYNOPSIS .Nm grep .Bk -words -.Op Fl abcEFGHhIiLlnqRsUVvwxZ +.Op Fl abcEFGHhIiLlnoqRsUVvwxZ .Op Fl A Ar num .Op Fl B Ar num .Op Fl C Ns Op Ar num @@ -228,6 +228,8 @@ .Fl q is specified. +.It Fl o +Print each match, but only the match, not the containing line. .It Fl q Quiet mode: suppress normal output. Index: grep.c =================================================================== RCS file: /home/tedu/cvs/src/usr.bin/grep/grep.c,v retrieving revision 1.43 diff -u -r1.43 grep.c --- grep.c 4 Mar 2011 03:11:23 -0000 1.43 +++ grep.c 20 Jun 2011 19:36:39 -0000 @@ -74,6 +74,7 @@ int iflag; /* -i: ignore case */ int lflag; /* -l: only show names of files with matches */ int nflag; /* -n: show line numbers in front of matching lines */ +int oflag; /* -o: print each match */ int qflag; /* -q: quiet mode (don't output anything) */ int sflag; /* -s: silent mode (ignore errors) */ int vflag; /* -v: only show non-matching lines */ @@ -117,9 +118,9 @@ } #ifdef NOZ -static char *optstr = "0123456789A:B:CEFGHILRUVabce:f:hilnqrsuvwxy"; +static char *optstr = "0123456789A:B:CEFGHILRUVabce:f:hilnoqrsuvwxy"; #else -static char *optstr = "0123456789A:B:CEFGHILRUVZabce:f:hilnqrsuvwxy"; +static char *optstr = "0123456789A:B:CEFGHILRUVZabce:f:hilnoqrsuvwxy"; #endif struct option long_options[] = @@ -382,6 +383,9 @@ break; case 'n': nflag = 1; + break; + case 'o': + oflag = 1; break; case 'q': qflag = 1; Index: grep.h =================================================================== RCS file: /home/tedu/cvs/src/usr.bin/grep/grep.h,v retrieving revision 1.16 diff -u -r1.16 grep.h --- grep.h 4 Mar 2011 03:11:23 -0000 1.16 +++ grep.h 20 Jun 2011 19:34:58 -0000 @@ -65,7 +65,7 @@ /* Command line flags */ extern int Aflag, Bflag, Eflag, Fflag, Gflag, Hflag, Lflag, Rflag, Zflag, - bflag, cflag, hflag, iflag, lflag, nflag, qflag, sflag, + bflag, cflag, hflag, iflag, lflag, nflag, oflag, qflag, sflag, vflag, wflag, xflag; extern int binbehave; @@ -84,7 +84,7 @@ void *grep_malloc(size_t size); void *grep_calloc(size_t nmemb, size_t size); void *grep_realloc(void *ptr, size_t size); -void printline(str_t *line, int sep); +void printline(str_t *line, int sep, regmatch_t *pmatch); int fastcomp(fastgrep_t *, const char *); void fgrepcomp(fastgrep_t *, const char *); Index: queue.c =================================================================== RCS file: /home/tedu/cvs/src/usr.bin/grep/queue.c,v retrieving revision 1.5 diff -u -r1.5 queue.c --- queue.c 9 Feb 2006 09:54:47 -0000 1.5 +++ queue.c 20 Jun 2011 19:33:23 -0000 @@ -107,7 +107,7 @@ queue_t *item; while ((item = dequeue()) != NULL) { - printline(&item->data, '-'); + printline(&item->data, '-', NULL); free_item(item); } } Index: util.c =================================================================== RCS file: /home/tedu/cvs/src/usr.bin/grep/util.c,v retrieving revision 1.39 diff -u -r1.39 util.c --- util.c 2 Jul 2010 22:18:03 -0000 1.39 +++ util.c 20 Jun 2011 19:34:30 -0000 @@ -48,9 +48,9 @@ static int linesqueued; static int procline(str_t *l, int); -static int grep_search(fastgrep_t *, unsigned char *, size_t, regmatch_t *pmatch); +static int grep_search(fastgrep_t *, char *, size_t, regmatch_t *pmatch); #ifndef SMALL -static int grep_cmp(const unsigned char *, const unsigned char *, size_t); +static int grep_cmp(const char *, const char *, size_t); static void grep_revstr(unsigned char *, int); #endif @@ -169,19 +169,25 @@ { regmatch_t pmatch; int c, i, r; + int offset; + c = 0; + i = 0; if (matchall) { - c = !vflag; goto print; } - for (c = i = 0; i < patterns; i++) { + for (i = 0; i < patterns; i++) { + offset = 0; +redo: if (fg_pattern[i].pattern) { - r = grep_search(&fg_pattern[i], (unsigned char *)l->dat, - l->len, &pmatch); + r = grep_search(&fg_pattern[i], l->dat + offset, + l->len - offset, &pmatch); + pmatch.rm_so += offset; + pmatch.rm_eo += offset; } else { - pmatch.rm_so = 0; - pmatch.rm_eo = l->len; + pmatch.rm_so = offset; + pmatch.rm_eo = l->len - offset; r = regexec(&r_pattern[i], l->dat, 1, &pmatch, eflags); } if (r == 0 && xflag) { @@ -189,14 +195,18 @@ r = REG_NOMATCH; } if (r == 0) { - c++; + c = 1; + if (oflag) + goto print; break; } } + if (oflag) + return c; +print: if (vflag) c = !c; -print: if (c && binbehave == BIN_FILE_BIN && nottext) return c; /* Binary file */ @@ -210,12 +220,17 @@ if (Bflag > 0) printqueue(); linesqueued = 0; - printline(l, ':'); + printline(l, ':', oflag ? &pmatch : NULL); } else { - printline(l, '-'); + printline(l, '-', oflag ? &pmatch : NULL); tail--; } } + if (oflag && !matchall) { + + offset = pmatch.rm_eo; + goto redo; + } return c; } @@ -424,7 +439,7 @@ e > s && isword(d[s]) && isword(d[e-1])) static int -grep_search(fastgrep_t *fg, unsigned char *data, size_t dataLen, regmatch_t *pmatch) +grep_search(fastgrep_t *fg, char *data, size_t dataLen, regmatch_t *pmatch) { #ifdef SMALL return 0; @@ -476,7 +491,7 @@ /* Shift if within bounds, otherwise, we are done. */ if (j == fg->patternLen) break; - j -= fg->qsBc[data[j - fg->patternLen - 1]]; + j -= fg->qsBc[(unsigned char)data[j - fg->patternLen - 1]]; } while (j >= fg->patternLen); } else { /* Quick Search algorithm. */ @@ -497,7 +512,7 @@ if (j + fg->patternLen == dataLen) break; else - j += fg->qsBc[data[j + fg->patternLen]]; + j += fg->qsBc[(unsigned char)data[j + fg->patternLen]]; } while (j <= (dataLen - fg->patternLen)); } @@ -540,7 +555,7 @@ * -1 on success */ static int -grep_cmp(const unsigned char *pattern, const unsigned char *data, size_t len) +grep_cmp(const char *pattern, const char *data, size_t len) { int i; @@ -569,7 +584,7 @@ #endif void -printline(str_t *line, int sep) +printline(str_t *line, int sep, regmatch_t *pmatch) { int n; @@ -592,6 +607,10 @@ } if (n) putchar(sep); - fwrite(line->dat, line->len, 1, stdout); + if (pmatch) + fwrite(line->dat + pmatch->rm_so, + pmatch->rm_eo - pmatch->rm_so, 1, stdout); + else + fwrite(line->dat, line->len, 1, stdout); putchar('\n'); }