id: add -z, --zero option

* src/group-list.h (print_group_list): Add a parameter for the
delimiter of type char.
* src/group-list.c (print_group_list): Likewise, and use it instead
of a white space character to delimit the group entries.
* src/groups.c (main): Pass white space character to print_group_list().
* src/id.c (longopts):  Add array element for the new long option.
(usage): Document the new option.  While at it, fix the alignment
of the descriptions to match that of HELP_OPTION_DESCRIPTION.
(main): Define the bool flag opt_zero indicating the use of the
new option.  In the getopt_long loop, handle it.
Output an error diagnostic in the case the --zero option has been
specified together with the default format.
In the case of -gG, pass either a NUL or a white space character to
print_group_list() - depending on the above new flag.
Likewise change the printing of the final newline character: output
a NUL instead if the --zero option has been specified.
* doc/coreutils.texi (id invocation): Document the new option.
While at it, move the @exitstatus macro down after the macro
@primaryAndSupplementaryGroups in order to be consistent with
other texinfo documents.
(groups invocation): Move @exitstatus down after the macro
@primaryAndSupplementaryGroups here, too.
* tests/misc/id-zero.sh: Add new test exercising the new option.
* tests/local.mk (all_tests): Reference it.
* NEWS (New features): Mention the new option.
Fixes http://bugs.gnu.org/9987

4 files changed, 32 insertions, 18 deletions

diff --git a/src/group-list.c b/src/group-list.c
index 7d4995b5c..d54b05776 100644
--- a/src/group-list.c
+++ b/src/group-list.c
@@ -35,7 +35,7 @@
 extern bool
 print_group_list (const char *username,
                   uid_t ruid, gid_t rgid, gid_t egid,
-                  bool use_names)
+                  bool use_names, char delim)
 {
   bool ok = true;
   struct passwd *pwd = NULL;
@@ -52,7 +52,7 @@ print_group_list (const char *username,
 
   if (egid != rgid)
     {
-      putchar (' ');
+      putchar (delim);
       if (!print_group (egid, use_names))
         ok = false;
     }
@@ -79,7 +79,7 @@ print_group_list (const char *username,
     for (i = 0; i < n_groups; i++)
       if (groups[i] != rgid && groups[i] != egid)
         {
-          putchar (' ');
+          putchar (delim);
           if (!print_group (groups[i], use_names))
             ok = false;
         }
diff --git a/src/group-list.h b/src/group-list.h
index 3fac88719..573de1def 100644
--- a/src/group-list.h
+++ b/src/group-list.h
@@ -16,4 +16,4 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 bool print_group (gid_t, bool);
-bool print_group_list (const char *, uid_t, gid_t, gid_t, bool);
+bool print_group_list (const char *, uid_t, gid_t, gid_t, bool, char);
diff --git a/src/groups.c b/src/groups.c
index 53332d56b..d30c9fb41 100644
--- a/src/groups.c
+++ b/src/groups.c
@@ -114,13 +114,13 @@ main (int argc, char **argv)
       if (rgid == NO_GID && errno)
         error (EXIT_FAILURE, errno, _("cannot get real GID"));
 
-      if (!print_group_list (NULL, ruid, rgid, egid, true))
+      if (!print_group_list (NULL, ruid, rgid, egid, true, ' '))
         ok = false;
       putchar ('\n');
     }
   else
     {
-      /* At least one argument.  Divulge the details of the specified users. */
+      /* At least one argument.  Divulge the details of the specified users.  */
       while (optind < argc)
         {
           struct passwd *pwd = getpwnam (argv[optind]);
@@ -130,7 +130,7 @@ main (int argc, char **argv)
           rgid = egid = pwd->pw_gid;
 
           printf ("%s : ", argv[optind]);
-          if (!print_group_list (argv[optind++], ruid, rgid, egid, true))
+          if (!print_group_list (argv[optind++], ruid, rgid, egid, true, ' '))
             ok = false;
           putchar ('\n');
         }
diff --git a/src/id.c b/src/id.c
index 3e7016f7b..a0334ba73 100644
--- a/src/id.c
+++ b/src/id.c
@@ -67,6 +67,7 @@ static struct option const longopts[] =
   {"name", no_argument, NULL, 'n'},
   {"real", no_argument, NULL, 'r'},
   {"user", no_argument, NULL, 'u'},
+  {"zero", no_argument, NULL, 'z'},
   {GETOPT_HELP_OPTION_DECL},
   {GETOPT_VERSION_OPTION_DECL},
   {NULL, 0, NULL, 0}
@@ -83,14 +84,18 @@ usage (int status)
       fputs (_("\
 Print user and group information for the specified USERNAME,\n\
 or (when USERNAME omitted) for the current user.\n\
-\n\
-  -a              ignore, for compatibility with other versions\n\
-  -Z, --context   print only the security context of the current user\n\
-  -g, --group     print only the effective group ID\n\
-  -G, --groups    print all group IDs\n\
-  -n, --name      print a name instead of a number, for -ugG\n\
-  -r, --real      print the real ID instead of the effective ID, with -ugG\n\
-  -u, --user      print only the effective user ID\n\
+\n"),
+             stdout);
+      fputs (_("\
+  -a             ignore, for compatibility with other versions\n\
+  -Z, --context  print only the security context of the current user\n\
+  -g, --group    print only the effective group ID\n\
+  -G, --groups   print all group IDs\n\
+  -n, --name     print a name instead of a number, for -ugG\n\
+  -r, --real     print the real ID instead of the effective ID, with -ugG\n\
+  -u, --user     print only the effective user ID\n\
+  -z, --zero     delimit entries with NUL characters, not whitespace;\n\
+                   not permitted in default format\n\
 "), stdout);
       fputs (HELP_OPTION_DESCRIPTION, stdout);
       fputs (VERSION_OPTION_DESCRIPTION, stdout);
@@ -109,6 +114,7 @@ main (int argc, char **argv)
   int optc;
   int selinux_enabled = (is_selinux_enabled () > 0);
   bool smack_enabled = is_smack_enabled ();
+  bool opt_zero = false;
 
   /* If true, output the list of all group IDs. -G */
   bool just_group_list = false;
@@ -127,7 +133,7 @@ main (int argc, char **argv)
 
   atexit (close_stdout);
 
-  while ((optc = getopt_long (argc, argv, "agnruGZ", longopts, NULL)) != -1)
+  while ((optc = getopt_long (argc, argv, "agnruzGZ", longopts, NULL)) != -1)
     {
       switch (optc)
         {
@@ -162,6 +168,9 @@ main (int argc, char **argv)
         case 'u':
           just_user = true;
           break;
+        case 'z':
+          opt_zero = true;
+          break;
         case 'G':
           just_group_list = true;
           break;
@@ -193,6 +202,10 @@ main (int argc, char **argv)
     error (EXIT_FAILURE, 0,
            _("cannot print only names or real IDs in default format"));
 
+  if (default_format && opt_zero)
+    error (EXIT_FAILURE, 0,
+           _("option --zero not permitted in default format"));
+
   /* If we are on a SELinux/SMACK-enabled kernel, no user is specified, and
      either --context is specified or none of (-u,-g,-G) is specified,
      and we're not in POSIXLY_CORRECT mode, get our context.  Otherwise,
@@ -269,7 +282,8 @@ main (int argc, char **argv)
     }
   else if (just_group_list)
     {
-      if (!print_group_list (argv[optind], ruid, rgid, egid, use_name))
+      if (!print_group_list (argv[optind], ruid, rgid, egid, use_name,
+                             opt_zero ? '\0' : ' '))
         ok = false;
     }
   else if (just_context)
@@ -280,7 +294,7 @@ main (int argc, char **argv)
     {
       print_full_info (argv[optind]);
     }
-  putchar ('\n');
+  putchar (opt_zero ? '\0' : '\n');
 
   exit (ok ? EXIT_SUCCESS : EXIT_FAILURE);
 }