grep -E

grep.1

@@ -3,7 +3,7 @@
 grep \- search files for a pattern
 .SH SYNOPSIS
 .B grep
-.RB [ \-cilnqv ]
+.RB [ \-Ecilnqv ]
 .I pattern
 .RI [ file ...]
 .SH DESCRIPTION
@@ -17,6 +17,9 @@ The status code is 0 if any lines match, and 1 if not.  If an error occurred the
 status code is 2.
 .SH OPTIONS
 .TP
+.B \-E
+matches using extended regex.
+.TP
 .B \-c
 prints only a count of matching lines.
 .TP

grep.c

@@ -8,6 +8,7 @@
 
 static void grep(FILE *, const char *, regex_t *);
 
+static bool Eflag = false;
 static bool iflag = false;
 static bool vflag = false;
 static bool many;
@@ -22,8 +23,11 @@ main(int argc, char *argv[])
 	regex_t preg;
 	FILE *fp;
 
-	while((c = getopt(argc, argv, "cilnqv")) != -1)
+	while((c = getopt(argc, argv, "Ecilnqv")) != -1)
 		switch(c) {
+		case 'E':
+			Eflag = true;
+			break;
 		case 'c':
 		case 'l':
 		case 'n':
@@ -43,6 +47,8 @@ main(int argc, char *argv[])
 		fprintf(stderr, "usage: %s [-cilnqv] pattern [files...]\n", argv[0]);
 		exit(2);
 	}
+	if(Eflag)
+		flags |= REG_EXTENDED;
 	if(iflag)
 		flags |= REG_ICASE;
 	regcomp(&preg, argv[optind++], flags);