cmp(1): Provide some long options

These match GNU cmp(1) for compatibility where applicable.

Future work might implement the -i option from GNU cmp(1) to express skip
either in terms of both files or of the form "SKIP1:SKIP2" rather than
specifying them as additional arguments to cmp(1).

MFC after:	1 month

2 files changed, 13 insertions, 4 deletions

diff --git a/usr.bin/cmp/cmp.1 b/usr.bin/cmp/cmp.1
index 1264604bbde9..f3bfdf651b51 100644
--- a/usr.bin/cmp/cmp.1
+++ b/usr.bin/cmp/cmp.1
@@ -31,7 +31,7 @@
 .\"     @(#)cmp.1	8.1 (Berkeley) 6/6/93
 .\" $FreeBSD$
 .\"
-.Dd November 18, 2013
+.Dd May 1, 2018
 .Dt CMP 1
 .Os
 .Sh NAME
@@ -59,10 +59,10 @@ The following options are available:
 .Bl -tag -width indent
 .It Fl h
 Do not follow symbolic links.
-.It Fl l
+.It Fl l , Fl -verbose
 Print the byte number (decimal) and the differing
 byte values (octal) for each difference.
-.It Fl s
+.It Fl s , Fl -silent , Fl -quiet
 Print nothing for differing files; return exit
 status only.
 .It Fl x
diff --git a/usr.bin/cmp/cmp.c b/usr.bin/cmp/cmp.c
index ea67a939d5b0..b47df0c8da7a 100644
--- a/usr.bin/cmp/cmp.c
+++ b/usr.bin/cmp/cmp.c
@@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
 #include <err.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <getopt.h>
 #include <nl_types.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -62,6 +63,14 @@ __FBSDID("$FreeBSD$");
 
 int	lflag, sflag, xflag, zflag;
 
+static const struct option long_opts[] =
+{
+	{"verbose",	no_argument,		NULL, 'l'},
+	{"silent",	no_argument,		NULL, 's'},
+	{"quiet",	no_argument,		NULL, 's'},
+	{NULL,		no_argument,		NULL, 0}
+};
+
 static void usage(void);
 
 int
@@ -75,7 +84,7 @@ main(int argc, char *argv[])
 	uint32_t fcntls;
 
 	oflag = O_RDONLY;
-	while ((ch = getopt(argc, argv, "hlsxz")) != -1)
+	while ((ch = getopt_long(argc, argv, "+hlsxz", long_opts, NULL)) != -1)
 		switch (ch) {
 		case 'h':		/* Don't follow symlinks */
 			oflag |= O_NOFOLLOW;