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.

4 files changed, 46 insertions, 6 deletions

diff --git a/THANKS b/THANKS
index 4c47877..45b0dfb 100644
--- a/THANKS
+++ b/THANKS
@@ -14,6 +14,7 @@ Brian Mays              <brian@debian.org>
 Clint Adams             <schizo@debian.org>
 Dmitry V. Levin         <ldv@altlinux.org>
 Jim Castleberry         <bhg9aha02@sneakemail.com>
+Joshua Briefman 	<sirgatez@gmail.com>
 Holger Fleischmann	<holger_fleischmann@mra.man.de>
 Ladislav Michnovič	<ladislav.michnovic@gmail.com>
 Matthew Braithwaite     <mab@cnet.com>
diff --git a/doc/cpio.1 b/doc/cpio.1
index 53f9395..d48d2df 100644
--- a/doc/cpio.1
+++ b/doc/cpio.1
@@ -13,7 +13,7 @@
 .\"
 .\" You should have received a copy of the GNU General Public License
 .\" along with GNU cpio.  If not, see <http://www.gnu.org/licenses/>.
-.TH CPIO 1 "January 29, 2014" "CPIO" "GNU CPIO"
+.TH CPIO 1 "January 30, 2014" "CPIO" "GNU CPIO"
 .SH NAME
 cpio \- copy files to and from archives
 .SH SYNOPSIS
@@ -182,6 +182,14 @@ files differently).
 In copy-in and copy-pass mode, set the ownership of all files created
 to the specified \fIUSER\fR and/or \fIGROUP\fR.  In copy-out mode,
 store the supplied owner information in the archive.
+
+\fIUSER\fR and \fIGROUP\fR are first looked up in the system user and
+group databases.  If not found, \fBcpio\fR checks if they consist of
+decimal digits only and, if so, treats them as numeric UID and GID,
+correspondingly.
+
+To avoid the lookup and ensure that arguments are treated as numeric
+values, prefix them with a plus sign, e.g.: \fB-R +0:+0\fR.
 .TP
 .B \-\-quiet
 Do not print the number of blocks copied at the end of the run.
diff --git a/doc/cpio.texi b/doc/cpio.texi
index 5a739ab..7c60d5f 100644
--- a/doc/cpio.texi
+++ b/doc/cpio.texi
@@ -295,7 +295,7 @@ Use @var{command} instead of @command{rsh} to access remote archives.
 @item -R
 @itemx --owner=[@var{user}][:.][@var{group}]
 Set the ownership of all files created to the specified @var{user}
-and/or @var{group}.
+and/or @var{group}.  @xref{owner}.
 @item -v
 @itemx --verbose
 Verbosely list the files processed.
@@ -515,7 +515,7 @@ Interactively rename files
 @item -R
 @itemx --owner=[@var{user}][:.][@var{group}]
 Set the ownership of all files created to the specified @var{user}
-and/or @var{group}.
+and/or @var{group}.  @xref{owner}.
 @item -s
 @itemx --swap-bytes
 Swap the bytes of each halfword in the files
@@ -796,6 +796,7 @@ Run in copy-pass mode.
 [@ref{copy-in}]
 @*Interactively rename files.
 
+@anchor{owner}
 @item -R @var{owner}
 @itemx --owner @var{owner}
 [@ref{copy-in},@ref{copy-out},@ref{copy-pass}]
@@ -817,6 +818,23 @@ cpio --owner :users
 @end group
 @end smallexample
 
+The argument parts are first looked up in the system user and
+group databases, correspondingly.  If any of them is not found there,
+it is treated as numeric UID or GID, provided that it consists of
+decimal digits only.
+
+To avoid the lookup and ensure that arguments are treated as numeric
+values, prefix them with a plus sign, e.g.:
+
+@smallexample
+@group
+cpio --owner +0
+cpio --owner +0:
+cpio --owner +0:+0
+cpio --owner :+0
+@end group
+@end smallexample
+
 @noindent
 If the group is omitted but the @samp{:} or @samp{.} separator is
 given, as in the second example. the given user's login group will be
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)
     {
-      pwd = getpwnam (u);
-      if (pwd == 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.  */
-      grp = getgrnam (g);
+      if (*g == '+')
+	{
+	  grp = NULL;
+	  ++g;
+	}
+      else
+	grp = getgrnam (g);
+
       if (grp == NULL)
 	{
 	  if (!isnumber_p (g))