- Be explicit on command line checking, instead of relying on patterns,

  which may be NULL (e.g. -e '').
- let add_pattern() decide how to deal with empty patterns, don't do
  magic in read_patterns().

This unbreaks stuff like grep -e '', and makes grep -f <file> more
POSIX compliant. Semantics for grep -f /dev/null (or any other empty
file) may be questionable, but this case isn't specified by POSIX,
and matching nothing at all seems to be sane.

Thanks to otto@, who mentioned potential problems related to the
-x option with the first patch i sent.

ok jaredy@ (some time ago), otto@, millert@

grep.1

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: grep.1,v 1.31 2005/06/05 19:40:22 jmc Exp $
+.\"	$OpenBSD: grep.1,v 1.32 2006/03/07 12:23:50 jmc Exp $
 .\" Copyright (c) 1980, 1990, 1993
 .\"	The Regents of the University of California.  All rights reserved.
 .\"
@@ -170,7 +170,11 @@ to behave as
 .It Fl f Ar file
 Read one or more newline separated patterns from
 .Ar file .
+Empty pattern lines match every input line.
 Newlines are not considered part of a pattern.
+If
+.Ar file
+is empty, nothing is matched.
 .It Fl G
 Interpret
 .Ar pattern
@@ -364,7 +368,9 @@ specification.
 .Pp
 The flags
 .Op Fl AaBbCGHhILoPRSUVwZ
-are extensions to that specification.
+are extensions to that specification, and the behaviour of the
+.Fl f
+flag when used with an empty pattern file is left undefined.
 .Pp
 All long options are provided for compatibility with
 GNU versions of this utility.

grep.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: grep.c,v 1.36 2006/09/26 15:55:17 jaredy Exp $	*/
+/*	$OpenBSD: grep.c,v 1.37 2006/11/02 18:00:03 ray Exp $	*/
 
 /*-
  * Copyright (c) 1999 James Howard and Dag-Erling Coïdan Smørgrav
@@ -221,23 +221,11 @@ read_patterns(const char *fn)
 	FILE *f;
 	char *line;
 	size_t len;
-	int nl;
 
 	if ((f = fopen(fn, "r")) == NULL)
 		err(2, "%s", fn);
-	nl = 0;
-	while ((line = fgetln(f, &len)) != NULL) {
-		if (*line == '\n') {
-			++nl;
-			continue;
-		}
-		if (nl) {
-			matchall = 1;
-			break;
-		}
-		nl = 0;
-		add_pattern(line, len);
-	}
+	while ((line = fgetln(f, &len)) != NULL)
+		add_pattern(line, *line == '\n' ? 0 : len);
 	if (ferror(f))
 		err(2, "%s", fn);
 	fclose(f);
@@ -246,7 +234,7 @@ read_patterns(const char *fn)
 int
 main(int argc, char *argv[])
 {
-	int c, lastc, prevoptind, newarg, i;
+	int c, lastc, prevoptind, newarg, i, needpattern;
 	struct patfile *patfile, *pf_next;
 	long l;
 	char *ep;
@@ -283,6 +271,7 @@ main(int argc, char *argv[])
 	lastc = '\0';
 	newarg = 1;
 	prevoptind = 1;
+	needpattern = 1;
 	while ((c = getopt_long(argc, argv, optstr,
 				long_options, NULL)) != -1) {
 		switch (c) {
@@ -372,11 +361,13 @@ main(int argc, char *argv[])
 			break;
 		case 'e':
 			add_patterns(optarg);
+			needpattern = 0;
 			break;
 		case 'f':
 			patfile = grep_malloc(sizeof(*patfile));
 			patfile->pf_file = optarg;
 			SLIST_INSERT_HEAD(&patfilelh, patfile, pf_next);
+			needpattern = 0;
 			break;
 		case 'h':
 			oflag = 0;
@@ -448,10 +439,10 @@ main(int argc, char *argv[])
 		free(patfile);
 	}
 
-	if (argc == 0 && patterns == 0)
+	if (argc == 0 && needpattern)
 		usage();
 
-	if (patterns == 0) {
+	if (argc != 0 && needpattern) {
 		add_patterns(*argv);
 		--argc;
 		++argv;