id: output the effective group for the process

* src/id.c (print_full_info): When no user is specified,
output the effective group for the _process_, rather than
the default group from the system database, which may be different.
* tests/id/setgid.sh: Add a case for `id` as well as `id -G`.
* NEWS: Mention the bug fix.
Fixes http://bugs.gnu.org/7320
Reported at http://bugzilla.redhat.com/1016163

1 files changed, 10 insertions, 9 deletions

diff --git a/src/id.c b/src/id.c
index 3348f8013..f46bb41b5 100644
--- a/src/id.c
+++ b/src/id.c
@@ -399,19 +399,20 @@ print_full_info (const char *username)
     gid_t *groups;
     int i;
 
-    int n_groups = xgetgroups (username, (pwd ? pwd->pw_gid : -1),
-                               &groups);
+    gid_t primary_group;
+    if (username)
+      primary_group = pwd ? pwd->pw_gid : -1;
+    else
+      primary_group = egid;
+
+    int n_groups = xgetgroups (username, primary_group, &groups);
     if (n_groups < 0)
       {
         if (username)
-          {
-            error (0, errno, _("failed to get groups for user %s"),
-                   quote (username));
-          }
+          error (0, errno, _("failed to get groups for user %s"),
+                 quote (username));
         else
-          {
-            error (0, errno, _("failed to get groups for the current process"));
-          }
+          error (0, errno, _("failed to get groups for the current process"));
         ok = false;
         return;
       }