Seems to me that a recursive chown/chgrp, in a large directory with
_most_but_not_all files already set to the desired owner/group, can
be rather wastefull. As near as I can tell, the kernel is called
for every file, even those for whom the update of attributes is
effectively a no-op. Further, these no-op calls apparently trigger
other non-updates to the filesystem whjich can affect files' mtime
and/or atime.
(FWIW, I frequently end up with such a directory when a CVS update
picks up a new file and I forgot to su(8) to the owner's UID first!
The new files get my current owner uid while all the other files
are owned by someone else.)
I propose the attached enhancement to chown/chgrp to avoid setting
a new user/group value if the desired values are already set. The
change is pretty simple.
Note that this change also modifies the changes that might be made
to a file's setuid/setgid mode bits. Current code simply clears the
bits for every file, whether or not the user/group is really being
updated. The attached patch only clears the bits if the user/group
is also being _changed_ from its current value.
Comments? Useful? Suggestions? Should I commit?
+--------------------+--------------------------+----------------------+
| Paul Goyette | PGP Key fingerprint: | E-mail addresses: |
| (Retired) | FA29 0E3B 35AF E8AE 6651 | p...@whooppee.com |
| Software Developer | 0786 F758 55DE 53BA 7731 | pgoye...@netbsd.org |
| & Network Engineer | | pgoyett...@gmail.com |
+--------------------+--------------------------+----------------------+
Index: chgrp.1
===================================================================
RCS file: /cvsroot/src/sbin/chown/chgrp.1,v
retrieving revision 1.8
diff -u -p -r1.8 chgrp.1
--- chgrp.1 4 Jul 2017 06:52:20 -0000 1.8
+++ chgrp.1 28 Apr 2023 19:01:05 -0000
@@ -31,7 +31,7 @@
.\" from: @(#)chgrp.1 8.3 (Berkeley) 3/31/94
.\" $NetBSD: chgrp.1,v 1.8 2017/07/04 06:52:20 wiz Exp $
.\"
-.Dd October 22, 2012
+.Dd May 1, 2023
.Dt CHGRP 1
.Os
.Sh NAME
@@ -86,6 +86,9 @@ option is specified, no symbolic links a
.It Fl R
Change the group ID for the file hierarchies rooted
in the files instead of just the files themselves.
+.It Fl d
+Do not attempt to update a file's group if it is already set to the
+desired value.
.It Fl f
The force option ignores errors, except for usage errors and doesn't
query about strange modes (unless the user does not have proper permissions).
@@ -164,6 +167,8 @@ utility is expected to be POSIX 1003.2 c
.Pp
The
.Fl v
-option and the use of ``#'' to force a numeric group ID
+and
+.Fl d
+options and the use of ``#'' to force a numeric group ID
are extensions to
.St -p1003.2 .
Index: chown.8
===================================================================
RCS file: /cvsroot/src/sbin/chown/chown.8,v
retrieving revision 1.12
diff -u -p -r1.12 chown.8
--- chown.8 4 Jul 2017 06:53:12 -0000 1.12
+++ chown.8 28 Apr 2023 19:01:05 -0000
@@ -28,7 +28,7 @@
.\" from: @(#)chown.8 8.3 (Berkeley) 3/31/94
.\" $NetBSD: chown.8,v 1.12 2017/07/04 06:53:12 wiz Exp $
.\"
-.Dd September 11, 2016
+.Dd May 1, 2023
.Dt CHOWN 8
.Os
.Sh NAME
@@ -84,6 +84,9 @@ option is specified, no symbolic links a
.It Fl R
Change the user ID and/or the group ID for the file hierarchies rooted
in the files instead of just the files themselves.
+.It Fl d
+Do not attempt to update a file's owner or group if it is already
+set to the desired value.
.It Fl f
Do not report any failure to change file owner or group, nor modify
the exit status to reflect such failures.
@@ -174,7 +177,9 @@ command is expected to be POSIX 1003.2 c
.Pp
The
.Fl v
-option and the use of ``#'' to force a numeric lookup
+and
+.Fl d
+options and the use of ``#'' to force a numeric lookup
are extensions to
.St -p1003.2 .
.Sh HISTORY
Index: chown.c
===================================================================
RCS file: /cvsroot/src/sbin/chown/chown.c,v
retrieving revision 1.9
diff -u -p -r1.9 chown.c
--- chown.c 28 Apr 2023 09:56:45 -0000 1.9
+++ chown.c 28 Apr 2023 19:01:05 -0000
@@ -82,7 +82,7 @@ main(int argc, char **argv)
{
FTS *ftsp;
FTSENT *p;
- int Hflag, Lflag, Rflag, ch, fflag, fts_options, hflag, rval, vflag;
+ int Hflag, Lflag, Rflag, ch, fflag, fts_options, hflag, rval, vflag,
dflag;
char *cp, *reference;
int (*change_owner)(const char *, uid_t, gid_t);
@@ -94,13 +94,16 @@ main(int argc, char **argv)
ischown = (myname[2] == 'o');
reference = NULL;
- Hflag = Lflag = Rflag = fflag = hflag = vflag = 0;
- while ((ch = getopt_long(argc, argv, "HLPRfhv",
+ Hflag = Lflag = Rflag = fflag = hflag = vflag = dflag = 0;
+ while ((ch = getopt_long(argc, argv, "HLPRdfhv",
chown_longopts, NULL)) != -1)
switch (ch) {
case 1:
reference = optarg;
break;
+ case 'd':
+ dflag = 1;
+ break;
case 'H':
Hflag = 1;
Lflag = 0;
@@ -232,6 +235,15 @@ main(int argc, char **argv)
break;
}
+ /*
+ * If dflag was set, and the owner and group are already
+ * set to the right value, skip any attempt to update.
+ */
+ if (dflag &&
+ ( uid == -1 || p->fts_statp->st_uid == uid ) &&
+ ( gid == -1 || p->fts_statp->st_gid == gid ))
+ continue;
+
if ((*change_owner)(p->fts_accpath, uid, gid) && !fflag) {
warn("%s", p->fts_path);
rval = EXIT_FAILURE;
@@ -294,8 +306,8 @@ usage(void)
{
(void)fprintf(stderr,
- "Usage: %s [-R [-H | -L | -P]] [-fhv] %s file ...\n"
- "\t%s [-R [-H | -L | -P]] [-fhv] --reference=rfile file ...\n",
+ "Usage: %s [-R [-H | -L | -P]] [-dfhv] %s file ...\n"
+ "\t%s [-R [-H | -L | -P]] [-dfhv] --reference=rfile file ...\n",
myname, ischown ? "owner:group|owner|:group" : "group",
myname);
exit(EXIT_FAILURE);
