Add code to export and print the description associated to sysctl

variables. Use the -d flag in sysctl(8) to see this information.

Possible extensions to sysctl:
 + report variables that do not have a description
 + given a name, report the oid it maps to.

Note to developers: have a look at your code, there are a number of
	variables which do not have a description.

Note to developers: do we want this in 4.5 ? It is a very small change
	and very useful for documentation purposes.

Suggested by: Orion Hodson

2 files changed, 19 insertions, 5 deletions

diff --git a/sbin/sysctl/sysctl.8 b/sbin/sysctl/sysctl.8
index f6c1bb9..ec2e054 100644
--- a/sbin/sysctl/sysctl.8
+++ b/sbin/sysctl/sysctl.8
@@ -44,7 +44,7 @@
 .Ar name Ns Op = Ns Ar value
 .Ar ...
 .Nm
-.Op Fl beNnox
+.Op Fl bdeNnox
 .Fl a
 .Sh DESCRIPTION
 The
@@ -71,6 +71,8 @@ the command line.
 Force the value of the variable(s) to be output in raw, binary format.
 No names are printed and no terminating newlines are output.
 This is mostly useful with a single variable.
+.It Fl d
+Print the description of the variable instead of its value.
 .It Fl e
 Separate the name and the value of the variable(s) with
 .Ql = .
diff --git a/sbin/sysctl/sysctl.c b/sbin/sysctl/sysctl.c
index 5ffb810..eb30b6e 100644
--- a/sbin/sysctl/sysctl.c
+++ b/sbin/sysctl/sysctl.c
@@ -58,7 +58,7 @@ static const char rcsid[] =
 #include <string.h>
 #include <unistd.h>
 
-static int	aflag, bflag, eflag, Nflag, nflag, oflag, xflag;
+static int	aflag, bflag, dflag, eflag, Nflag, nflag, oflag, xflag;
 
 static int	oidfmt(int *, int, char *, u_int *);
 static void	parse(char *);
@@ -71,8 +71,8 @@ usage(void)
 {
 
 	(void)fprintf(stderr, "%s\n%s\n",
-	    "usage: sysctl [-beNnox] variable[=value] ...",
-	    "       sysctl [-beNnox] -a");
+	    "usage: sysctl [-bdeNnox] variable[=value] ...",
+	    "       sysctl [-bdeNnox] -a");
 	exit(1);
 }
 
@@ -83,7 +83,7 @@ main(int argc, char **argv)
 	setbuf(stdout,0);
 	setbuf(stderr,0);
 
-	while ((ch = getopt(argc, argv, "AabeNnowxX")) != -1) {
+	while ((ch = getopt(argc, argv, "AabdeNnowxX")) != -1) {
 		switch (ch) {
 		case 'A':
 			/* compatibility */
@@ -95,6 +95,9 @@ main(int argc, char **argv)
 		case 'b':
 			bflag = 1;
 			break;
+		case 'd':
+			dflag = 1;
+			break;
 		case 'e':
 			eflag = 1;
 			break;
@@ -409,6 +412,15 @@ show_var(int *oid, int nlen)
 	else
 		sep = ": ";
 
+	if (dflag) {	/* just print description */
+		qoid[1] = 5;
+		j = sizeof(buf);
+		i = sysctl(qoid, nlen + 2, buf, &j, 0, 0);
+		if (!nflag)
+			printf("%s%s", name, sep);
+		printf("%s", buf);
+		return (0);
+	}
 	/* find an estimate of how much we need for this var */
 	j = 0;
 	i = sysctl(oid, nlen, 0, &j, 0, 0);