Add support for the non-standard grep -m extension.

grep -m num stops after a maximum of num matches are found.
We support -m0 to match GNU behaviour, but we do not allow negative
numbers.

Manpage help from jmc@, OK deraadt@.

4 files changed, 43 insertions, 12 deletions

diff --git a/usr.bin/grep/grep.1 b/usr.bin/grep/grep.1
index 6e8d7676df7..44fcf2c4851 100644
--- a/usr.bin/grep/grep.1
+++ b/usr.bin/grep/grep.1
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: grep.1,v 1.43 2015/01/13 04:45:34 daniel Exp $
+.\"	$OpenBSD: grep.1,v 1.44 2017/12/09 18:38:37 pirofti Exp $
 .\" Copyright (c) 1980, 1990, 1993
 .\"	The Regents of the University of California.  All rights reserved.
 .\"
@@ -28,7 +28,7 @@
 .\"
 .\"	@(#)grep.1	8.3 (Berkeley) 4/18/94
 .\"
-.Dd $Mdocdate: January 13 2015 $
+.Dd $Mdocdate: December 9 2017 $
 .Dt GREP 1
 .Os
 .Sh NAME
@@ -44,6 +44,7 @@
 .Op Fl C Ns Op Ar num
 .Op Fl e Ar pattern
 .Op Fl f Ar file
+.Op Fl m Ar num
 .Op Fl -binary-files Ns = Ns Ar value
 .Op Fl -context Ns Op = Ns Ar num
 .Op Fl -line-buffered
@@ -216,6 +217,10 @@ Pathnames are listed once per file searched.
 If the standard input is searched, the string
 .Dq (standard input)
 is written.
+.It Fl m Ar num, Fl Fl max-count Ns = Ns Ar num
+Stop after
+.Ar num
+matches.
 .It Fl n
 Each output line is preceded by its relative line number in the file,
 starting at line 1.
@@ -354,7 +359,7 @@ utility is compliant with the
 specification.
 .Pp
 The flags
-.Op Fl AaBbCGHhILoRUVwZ
+.Op Fl AaBbCGHhILmoRUVwZ
 are extensions to that specification, and the behaviour of the
 .Fl f
 flag when used with an empty pattern file is left undefined.
diff --git a/usr.bin/grep/grep.c b/usr.bin/grep/grep.c
index 907246caa5d..401ed503cbb 100644
--- a/usr.bin/grep/grep.c
+++ b/usr.bin/grep/grep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: grep.c,v 1.55 2015/11/28 01:17:12 gsoares Exp $	*/
+/*	$OpenBSD: grep.c,v 1.56 2017/12/09 18:38:37 pirofti Exp $	*/
 
 /*-
  * Copyright (c) 1999 James Howard and Dag-Erling Coïdan Smørgrav
@@ -71,6 +71,9 @@ int	 cflag;		/* -c: only show a count of matching lines */
 int	 hflag;		/* -h: don't print filename headers */
 int	 iflag;		/* -i: ignore case */
 int	 lflag;		/* -l: only show names of files with matches */
+int	 mflag;		/* -m x: stop reading the files after x matches */
+long long mcount;	/* count for -m */
+long long mlimit;	/* requested value for -m */
 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) */
@@ -111,15 +114,16 @@ usage(void)
 #else
 	    "usage: %s [-abcEFGHhIiLlnoqRsUVvwxZ] [-A num] [-B num] [-C[num]]\n"
 #endif
-	    "\t[-e pattern] [-f file] [--binary-files=value] [--context[=num]]\n"
-	    "\t[--line-buffered] [pattern] [file ...]\n", __progname);
+	    "\t[-e pattern] [-f file] [-m num] [--binary-files=value]\n"
+	    "\t[--context[=num]] [--line-buffered] [pattern] [file ...]\n",
+	    __progname);
 	exit(2);
 }
 
 #ifdef NOZ
-static const char optstr[] = "0123456789A:B:CEFGHILRUVabce:f:hilnoqrsuvwxy";
+static const char optstr[] = "0123456789A:B:CEFGHILRUVabce:f:hilm:noqrsuvwxy";
 #else
-static const char optstr[] = "0123456789A:B:CEFGHILRUVZabce:f:hilnoqrsuvwxy";
+static const char optstr[] = "0123456789A:B:CEFGHILRUVZabce:f:hilm:noqrsuvwxy";
 #endif
 
 static const struct option long_options[] =
@@ -147,6 +151,7 @@ static const struct option long_options[] =
 	{"ignore-case",		no_argument,		NULL, 'i'},
 	{"files-without-match",	no_argument,		NULL, 'L'},
 	{"files-with-matches",	no_argument,		NULL, 'l'},
+	{"max-count",		required_argument,	NULL, 'm'},
 	{"line-number",		no_argument,		NULL, 'n'},
 	{"quiet",		no_argument,		NULL, 'q'},
 	{"silent",		no_argument,		NULL, 'q'},
@@ -376,6 +381,14 @@ main(int argc, char *argv[])
 			Lflag = 0;
 			lflag = qflag = 1;
 			break;
+		case 'm':
+			mflag = 1;
+			mlimit = mcount = strtonum(optarg, 0, LLONG_MAX,
+			   &errstr);
+			if (errstr != NULL)
+				errx(2, "invalid max-count %s: %s",
+				    optarg, errstr);
+			break;
 		case 'n':
 			nflag = 1;
 			break;
diff --git a/usr.bin/grep/grep.h b/usr.bin/grep/grep.h
index 21b1cab10f8..bbf7f8cd8c8 100644
--- a/usr.bin/grep/grep.h
+++ b/usr.bin/grep/grep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: grep.h,v 1.24 2015/12/14 20:02:07 mmcc Exp $	*/
+/*	$OpenBSD: grep.h,v 1.25 2017/12/09 18:38:37 pirofti Exp $	*/
 
 /*-
  * Copyright (c) 1999 James Howard and Dag-Erling Coïdan Smørgrav
@@ -66,8 +66,8 @@ extern int	 cflags, eflags;
 /* Command line flags */
 extern int	 Aflag, Bflag, Eflag, Fflag, Hflag, Lflag,
 		 Rflag, Zflag,
-		 bflag, cflag, hflag, iflag, lflag, nflag, oflag, qflag, sflag,
-		 vflag, wflag, xflag;
+		 bflag, cflag, hflag, iflag, lflag, mflag, nflag, oflag, qflag,
+		 sflag, vflag, wflag, xflag;
 extern int	 binbehave;
 
 extern int	 first, matchall, patterns, tail, file_err;
@@ -75,6 +75,9 @@ extern char    **pattern;
 extern fastgrep_t *fg_pattern;
 extern regex_t	*r_pattern;
 
+/* For -m max-count */
+extern long long mcount, mlimit;
+
 /* For regex errors  */
 #define RE_ERROR_BUF 512
 extern char	 re_error[RE_ERROR_BUF + 1];	/* Seems big enough */
diff --git a/usr.bin/grep/util.c b/usr.bin/grep/util.c
index 9cfed4c0dae..f7c5407d3e0 100644
--- a/usr.bin/grep/util.c
+++ b/usr.bin/grep/util.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: util.c,v 1.57 2017/04/03 16:18:35 tedu Exp $	*/
+/*	$OpenBSD: util.c,v 1.58 2017/12/09 18:38:37 pirofti Exp $	*/
 
 /*-
  * Copyright (c) 1999 James Howard and Dag-Erling Coïdan Smørgrav
@@ -97,6 +97,8 @@ procfile(char *fn)
 	file_t *f;
 	int c, t, z, nottext;
 
+	mcount = mlimit;
+
 	if (fn == NULL) {
 		fn = "(standard input)";
 		f = grep_fdopen(STDIN_FILENO, "r");
@@ -126,6 +128,8 @@ procfile(char *fn)
 	if (Bflag > 0)
 		initqueue();
 	for (c = 0;  c == 0 || !(lflag || qflag); ) {
+		if (mflag && mlimit == 0)
+			break;
 		ln.off += ln.len + 1;
 		if ((ln.dat = grep_fgetln(f, &ln.len)) == NULL)
 			break;
@@ -140,6 +144,8 @@ procfile(char *fn)
 			linesqueued++;
 		}
 		c += t;
+		if (mflag && mcount <= 0)
+			break;
 	}
 	if (Bflag > 0)
 		clearqueue();
@@ -224,6 +230,10 @@ print:
 	if (vflag)
 		c = !c;
 
+	/* Count the matches if we have a match limit */
+	if (mflag)
+		mcount -= c;
+
 	if (c && binbehave == BIN_FILE_BIN && nottext)
 		return c; /* Binary file */