Treat UID/GID as numeric if prefixed by + (-R option)

The IDs supplied with the -R option are treated as numeric (without
looking them up in the system database), when prefixed with +.  This
allows to force using numeric value if a user (group) with a numeric
name exists in the database.

Reported by Joshua Briefman <sirgatez@gmail.com>.

* src/userspec.c (parse_user_spec): Use + as an indicator of
a numeric UID/GID.
* doc/cpio.1: Document changes.
* doc/cpio.texi: Likewise.

1 files changed, 14 insertions, 1 deletions

diff --git a/src/userspec.c b/src/userspec.c
index 8cffd65..82cfcef 100644
--- a/src/userspec.c
+++ b/src/userspec.c
@@ -108,10 +108,16 @@ parse_user_spec (const char *spec_arg, uid_t *uid, gid_t *gid,
 
   if (u != NULL)
     {
+      if (*u == '+')
+        {
+          pwd = NULL;
+          ++u;
+        }
+      else
         pwd = getpwnam (u);
+
       if (pwd == NULL)
         {
-
           if (!isnumber_p (u))
             error_msg = _("invalid user");
           else
@@ -155,7 +161,14 @@ parse_user_spec (const char *spec_arg, uid_t *uid, gid_t *gid,
   if (g != NULL && error_msg == NULL)
     {
       /* Explicit group.  */
+      if (*g == '+')
+        {
+          grp = NULL;
+          ++g;
+        }
+      else
         grp = getgrnam (g);
+
       if (grp == NULL)
         {
           if (!isnumber_p (g))