Add a --root command option to groupmems utility.

This option allows the utility to be chrooted when run under pseudo.

Signed-off-by: Mikhail Durnev <mikhail_durnev@mentor.com>

diff -Naur old/src/groupmems.c new/src/groupmems.c
--- old/src/groupmems.c	2011-02-13 11:58:16.000000000 -0600
+++ new/src/groupmems.c	2013-05-30 04:45:38.000000000 -0500
@@ -60,6 +60,7 @@
 #define EXIT_MEMBER_EXISTS	7	/* member of group already exists */
 #define EXIT_INVALID_USER	8	/* specified user does not exist */
 #define EXIT_INVALID_GROUP	9	/* specified group does not exist */
+#define EXIT_BAD_ARG		10	/* invalid argument to option */

 /*
  * Global variables
@@ -79,6 +80,7 @@
 static bool is_shadowgrp;
 static bool sgr_locked = false;
 #endif
+static const char *newroot = "";

 /* local function prototypes */
 static char *whoami (void);
@@ -368,6 +370,7 @@
	                "Options:\n"
	                "  -g, --group groupname         change groupname instead of the user's group\n"
	                "                                (root only)\n"
+	                "  -R, --root CHROOT_DIR         directory to chroot into\n"
	                "\n"
	                "Actions:\n"
	                "  -a, --add username            add username to the members of the group\n"
@@ -391,10 +394,11 @@
		{"group", required_argument, NULL, 'g'},
		{"list", no_argument, NULL, 'l'},
		{"purge", no_argument, NULL, 'p'},
+		{"root", required_argument, NULL, 'R'},
		{NULL, 0, NULL, '\0'}
	};

-	while ((arg = getopt_long (argc, argv, "a:d:g:lp", long_options,
+	while ((arg = getopt_long (argc, argv, "a:d:g:lpR:", long_options,
	                           &option_index)) != EOF) {
		switch (arg) {
		case 'a':
@@ -416,6 +420,28 @@
			purge = true;
			++exclusive;
			break;
+		case 'R':
+			if ('/' != optarg[0]) {
+				fprintf (stderr,
+					 _("%s: invalid chroot path '%s'\n"),
+					Prog, optarg);
+				exit (EXIT_BAD_ARG);
+			}
+			newroot = optarg;
+
+			if (access (newroot, F_OK) != 0) {
+				fprintf(stderr,
+					_("%s: chroot directory %s does not exist\n"),
+					Prog, newroot);
+				exit (EXIT_BAD_ARG);
+			}
+			if ( chroot(newroot) != 0 ) {
+				fprintf(stderr,
+					_("%s: unable to chroot to directory %s\n"),
+					Prog, newroot);
+				exit (EXIT_BAD_ARG);
+			}
+			break;
		default:
			usage ();
		}