[PATCH] id: add feature to accept multiple usernames

[Achilles Gaikwad]

Adds a feature to id command to accept multiple usernames and/or uid
as arguments.

$ id root nobody
uid=0(root) gid=0(root) groups=0(root)
uid=99(nobody) gid=99(nobody) groups=99(nobody)

* src/id.c (main): make varibles opt_zero, just_group_list,
just_group, use_real, just_user global to be used in a new
function.
(print_stuff): new function that will print user and group information
for the specified USER.
Restructure the code in the file to have global variables followed by
functions to make the file look pretty.

Signed-off-by: Achilles Gaikwad <address@hidden>
---
 src/id.c | 155 +++++++++++++++++++++++++++++--------------------------
 1 file changed, 82 insertions(+), 73 deletions(-)

diff --git a/src/id.c b/src/id.c
index be0758059..65117ec5c 100644
--- a/src/id.c
+++ b/src/id.c
@@ -43,10 +43,18 @@
 
 /* If nonzero, output only the SELinux context.  */
 static bool just_context = 0;
-
-static void print_user (uid_t uid);
-static void print_full_info (const char *username);
-
+/* If true, delimit entries with NUL characters, not whitespace */
+bool opt_zero = false;
+/* If true, output the list of all group IDs. -G */
+bool just_group_list = false;
+/* If true, output only the group ID(s). -g */
+bool just_group = false;
+/* If true, output real UID/GID instead of default effective UID/GID. -r */
+bool use_real = false;
+/* If true, output only the user ID(s). -u */
+bool just_user = false;
+/* True unless errors have been encountered.  */
+static bool ok = true;
 /* If true, output user/group name instead of ID number. -n */
 static bool use_name = false;
 
@@ -54,13 +62,14 @@ static bool use_name = false;
 static uid_t ruid, euid;
 static gid_t rgid, egid;
 
-/* True unless errors have been encountered.  */
-static bool ok = true;
-
 /* The SELinux context.  Start with a known invalid value so print_full_info
    knows when 'context' has not been set to a meaningful value.  */
 static char *context = NULL;
 
+static void print_user (uid_t uid);
+static void print_full_info (const char *username);
+static void print_stuff(const char *pw_name);
+
 static struct option const longopts[] =
 {
   {"context", no_argument, NULL, 'Z'},
@@ -116,18 +125,8 @@ main (int argc, char **argv)
   int optc;
   int selinux_enabled = (is_selinux_enabled () > 0);
   bool smack_enabled = is_smack_enabled ();
-  bool opt_zero = false;
   char *pw_name = NULL;
 
-  /* If true, output the list of all group IDs. -G */
-  bool just_group_list = false;
-  /* If true, output only the group ID(s). -g */
-  bool just_group = false;
-  /* If true, output real UID/GID instead of default effective UID/GID. -r */
-  bool use_real = false;
-  /* If true, output only the user ID(s). -u */
-  bool just_user = false;
-
   initialize_main (&argc, &argv);
   set_program_name (argv[0]);
   setlocale (LC_ALL, "");
@@ -185,11 +184,6 @@ main (int argc, char **argv)
     }
 
   size_t n_ids = argc - optind;
-  if (1 < n_ids)
-    {
-      error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
-      usage (EXIT_FAILURE);
-    }
 
   if (n_ids && just_context)
     die (EXIT_FAILURE, 0,
@@ -228,29 +222,43 @@ main (int argc, char **argv)
         die (EXIT_FAILURE, 0, _("can't get process context"));
     }
 
-  if (n_ids == 1)
-    {
-      struct passwd *pwd = NULL;
-      const char *spec = argv[optind];
-      /* Disallow an empty spec here as parse_user_spec() doesn't
-         give an error for that as it seems it's a valid way to
-         specify a noop or "reset special bits" depending on the system.  */
-      if (*spec)
-        {
-          if (parse_user_spec (spec, &euid, NULL, NULL, NULL) == NULL)
-            {
-              /* parse_user_spec will only extract a numeric spec,
-                 so we lookup that here to verify and also retrieve
-                 the PW_NAME used subsequently in group lookup.  */
-              pwd = getpwuid (euid);
-            }
-        }
-      if (pwd == NULL)
-        die (EXIT_FAILURE, 0, _("%s: no such user"), quote (spec));
-      pw_name = xstrdup (pwd->pw_name);
-      ruid = euid = pwd->pw_uid;
-      rgid = egid = pwd->pw_gid;
-    }
+  if (n_ids >= 1)
+  {
+      /* Changing the value of n_ids to the last index in the array where we
+         have the last possible user id. This helps us because we don't have
+         to declare a different variable to keep a track of where the last 
username
+         lies in argv[]. */
+      n_ids += optind;
+
+      /* For each username/userid to get its pw_name field */
+      for (; optind < n_ids; optind++)
+      {
+          struct passwd *pwd = NULL;
+          const char *spec = argv[optind];
+          /* Disallow an empty spec here as parse_user_spec() doesn't
+             give an error for that as it seems it's a valid way to
+             specify a noop or "reset special bits" depending on the system.  
*/
+          if (*spec) {
+              if (parse_user_spec(spec, &euid, NULL, NULL, NULL) == NULL) {
+                  /* parse_user_spec will only extract a numeric spec,
+                     so we lookup that here to verify and also retrieve
+                     the PW_NAME used subsequently in group lookup.  */
+                  pwd = getpwuid(euid);
+              }
+          }
+          if (pwd == NULL)
+          {
+                       error (0, errno, _("%s: no such user"), quote 
(argv[optind]));
+                       ok &= false;
+                       continue;
+                 }
+          pw_name = xstrdup(pwd->pw_name);
+          ruid = euid = pwd->pw_uid;
+          rgid = egid = pwd->pw_gid;
+          print_stuff(pw_name);
+          IF_LINT (free (pw_name));
+      }
+  }
   else
     {
       /* POSIX says identification functions (getuid, getgid, and
@@ -289,34 +297,10 @@ main (int argc, char **argv)
           if (rgid == NO_GID && errno)
             die (EXIT_FAILURE, errno, _("cannot get real GID"));
         }
+        print_stuff(pw_name);
+           IF_LINT (free (pw_name));
     }
 
-  if (just_user)
-    {
-      print_user (use_real ? ruid : euid);
-    }
-  else if (just_group)
-    {
-      if (!print_group (use_real ? rgid : egid, use_name))
-        ok = false;
-    }
-  else if (just_group_list)
-    {
-      if (!print_group_list (pw_name, ruid, rgid, egid, use_name,
-                             opt_zero ? '\0' : ' '))
-        ok = false;
-    }
-  else if (just_context)
-    {
-      fputs (context, stdout);
-    }
-  else
-    {
-      print_full_info (pw_name);
-    }
-  putchar (opt_zero ? '\0' : '\n');
-
-  IF_LINT (free (pw_name));
   return ok ? EXIT_SUCCESS : EXIT_FAILURE;
 }
 
@@ -356,7 +340,7 @@ print_user (uid_t uid)
         {
           error (0, 0, _("cannot find name for user ID %s"),
                  uidtostr (uid));
-          ok = false;
+          ok &= false;
         }
     }
 
@@ -415,7 +399,7 @@ print_full_info (const char *username)
                  quote (username));
         else
           error (0, errno, _("failed to get groups for the current process"));
-        ok = false;
+        ok &= false;
         return;
       }
 
@@ -438,3 +422,28 @@ print_full_info (const char *username)
   if (context)
     printf (_(" context=%s"), context);
 }
+
+/* Print information about the user based on the arguments passed. */
+
+static void
+print_stuff(const char *pw_name)
+{
+  if (just_user)
+      print_user (use_real ? ruid : euid);
+
+  /* print_group and print_group_lists functions return true on successful
+     execution but false if something goes wrong. We then AND this value with
+     the current value of 'ok' because we want to know if one of the previous
+     users faced a problem in these functions. This value of 'ok' is later used
+     to understand what status program should exit with. */
+  else if (just_group)
+         ok &= print_group (use_real ? rgid : egid, use_name);
+  else if (just_group_list)
+         ok &= print_group_list (pw_name, ruid, rgid, egid,
+                                        use_name, opt_zero ? '\0' : ' ');
+  else if (just_context)
+      fputs (context, stdout);
+  else
+      print_full_info (pw_name);
+  putchar (opt_zero ? '\0' : '\n');
+}
-- 
2.17.1