Implement -g and -u for id(1)

id.1

@@ -2,13 +2,19 @@
 .SH NAME
 \fBid\fR - Print real and effective user and group IDs
 .SH SYNOPSIS
-\fBid\fR [\fB-G\fR] \fR[\fIuser\fR|\fIuid\fR]
+\fBid\fR [\fB-g\fR] [\fB-u\fR] [\fB-G\fR] \fR[\fIuser\fR|\fIuid\fR]
 .SH DESCRIPTION
 \fBid\fR prints user and group information of the calling process to standard output.
 If a login name or uid is specified, the user and group information of that
 user is displayed.
 .SH OPTIONS
 .TP
+\fB-g\fR
+Print only the effective group ID.
+.TP
+\fB-u\fR
+Print only the effective user ID.
+.TP
 \fB-G\fR
 Display group information as whitespace separated numbers, in no particular order.
 .SH SEE ALSO

id.c

@@ -18,7 +18,7 @@ static void usernam(const char *nam);
 static void
 usage(void)
 {
-	eprintf("usage: %s [-G] [user | uid]\n", argv0);
+	eprintf("usage: %s [-g] [-u] [-G] [user | uid]\n", argv0);
 }
 
 static int Gflag = 0;
@@ -27,6 +27,12 @@ int
 main(int argc, char *argv[])
 {
 	ARGBEGIN {
+	case 'g':
+		printf("%d\n", getegid());
+		return EXIT_SUCCESS;
+	case 'u':
+		printf("%d\n", geteuid());
+		return EXIT_SUCCESS;
 	case 'G':
 		Gflag = 1;
 		break;