Add a -h option to tell cmp not to follow symbolic links.

MFC after:	3 weeks
Sponsored by:	Sophos/ActiveState

usr.bin/cmp/Makefile

@@ -2,6 +2,6 @@
 # $FreeBSD$
 
 PROG=	cmp
-SRCS=	cmp.c misc.c regular.c special.c
+SRCS=	cmp.c link.c misc.c regular.c special.c
 
 .include <bsd.prog.mk>

usr.bin/cmp/cmp.1

@@ -44,7 +44,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl l | Fl s | Fl x
-.Op Fl z
+.Op Fl hz
 .Ar file1 file2
 .Op Ar skip1 Op Ar skip2
 .Sh DESCRIPTION
@@ -61,6 +61,8 @@ Bytes and lines are numbered beginning with one.
 .Pp
 The following options are available:
 .Bl -tag -width flag
+.It Fl h
+Don't follow symbolic links.
 .It Fl l
 Print the byte number (decimal) and the differing
 byte values (octal) for each difference.

usr.bin/cmp/cmp.c

@@ -50,6 +50,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/stat.h>
 
 #include <err.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -67,11 +68,15 @@ main(int argc, char *argv[])
 {
 	struct stat sb1, sb2;
 	off_t skip1, skip2;
-	int ch, fd1, fd2, special;
+	int ch, fd1, fd2, oflag, special;
 	const char *file1, *file2;
 
-	while ((ch = getopt(argc, argv, "lsxz")) != -1)
+	oflag = O_RDONLY;
+	while ((ch = getopt(argc, argv, "hlsxz")) != -1)
 		switch (ch) {
+		case 'h':		/* Don't follow symlinks */
+			oflag |= O_NOFOLLOW;
+			break;
 		case 'l':		/* print all differences */
 			lflag = 1;
 			break;
@@ -106,7 +111,7 @@ main(int argc, char *argv[])
 		fd1 = 0;
 		file1 = "stdin";
 	}
-	else if ((fd1 = open(file1, O_RDONLY, 0)) < 0) {
+	else if ((fd1 = open(file1, oflag, 0)) < 0 && errno != EMLINK) {
 		if (!sflag)
 			err(ERR_EXIT, "%s", file1);
 		else
@@ -120,7 +125,7 @@ main(int argc, char *argv[])
 		fd2 = 0;
 		file2 = "stdin";
 	}
-	else if ((fd2 = open(file2, O_RDONLY, 0)) < 0) {
+	else if ((fd2 = open(file2, oflag, 0)) < 0 && errno != EMLINK) {
 		if (!sflag)
 			err(ERR_EXIT, "%s", file2);
 		else
@@ -130,6 +135,21 @@ main(int argc, char *argv[])
 	skip1 = argc > 2 ? strtol(argv[2], NULL, 0) : 0;
 	skip2 = argc == 4 ? strtol(argv[3], NULL, 0) : 0;
 
+	if (fd1 == -1) {
+		if (fd2 == -1) {
+			c_link(file1, skip1, file2, skip2);
+			exit(0);
+		} else if (!sflag)
+			errx(ERR_EXIT, "%s: Not a symbolic link", file2);
+		else
+			exit(ERR_EXIT);
+	} else if (fd2 == -1) {
+		if (!sflag)
+			errx(ERR_EXIT, "%s: Not a symbolic link", file1);
+		else
+			exit(ERR_EXIT);
+	}
+
 	if (!special) {
 		if (fstat(fd1, &sb1)) {
 			if (!sflag)
@@ -171,6 +191,6 @@ usage(void)
 {
 
 	(void)fprintf(stderr,
-	    "usage: cmp [-l | -s | -x] [-z] file1 file2 [skip1 [skip2]]\n");
+	    "usage: cmp [-l | -s | -x] [-hz] file1 file2 [skip1 [skip2]]\n");
 	exit(ERR_EXIT);
 }

usr.bin/cmp/extern.h

@@ -40,6 +40,7 @@
 #define DIFF_EXIT	1
 #define ERR_EXIT	2	/* error exit code */
 
+void	c_link(const char *, off_t, const char *, off_t);
 void	c_regular(int, const char *, off_t, off_t, int, const char *, off_t, off_t);
 void	c_special(int, const char *, off_t, int, const char *, off_t);
 void	diffmsg(const char *, const char *, off_t, off_t);

usr.bin/cmp/link.c

@@ -0,0 +1,93 @@
+/*-
+ * Copyright (c) 2005 Brian Somers <brian@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <err.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "extern.h"
+
+void
+c_link(const char *file1, off_t skip1, const char *file2, off_t skip2)
+{
+	char buf1[PATH_MAX], *p1;
+	char buf2[PATH_MAX], *p2;
+	int dfound, len1, len2;
+	off_t byte;
+	u_char ch;
+
+	if ((len1 = readlink(file1, buf1, sizeof(buf1) - 1)) < 0) {
+		if (!sflag)
+			err(ERR_EXIT, "%s", file1);
+		else
+			exit(ERR_EXIT);
+	}
+
+	if ((len2 = readlink(file2, buf2, sizeof(buf2) - 1)) < 0) {
+		if (!sflag)
+			err(ERR_EXIT, "%s", file2);
+		else
+			exit(ERR_EXIT);
+	}
+
+	if (skip1 > len1)
+		skip1 = len1;
+	buf1[len1] = '\0';
+
+	if (skip2 > len2)
+		skip2 = len2;
+	buf2[len2] = '\0';
+
+	dfound = 0;
+	byte = 1;
+	for (p1 = buf1 + skip1, p2 = buf2 + skip2; *p1 && *p2; p1++, p2++) {
+		if ((ch = *p1) != *p2) {
+			if (xflag) {
+				dfound = 1;
+				(void)printf("%08llx %02x %02x\n",
+				    (long long)byte - 1, ch, *p2);
+			} else if (lflag) {
+				dfound = 1;
+				(void)printf("%6lld %3o %3o\n",
+				    (long long)byte, ch, *p2);
+			} else
+				diffmsg(file1, file2, byte, 1);
+				/* NOTREACHED */
+		}
+		byte++;
+	}
+
+	if (*p1 || *p2)
+		eofmsg (*p1 ? file2 : file1);
+	if (dfound)
+		exit(DIFF_EXIT);
+}