Re: Portability of "mv -f"

[Ian Lance Taylor]

   From: Russ Allbery <address@hidden>
   Date: 21 Sep 2000 18:10:18 -0700

   > I believe that mv -f is fully portable.  I think the only portable
   > options to mv are -f and -i.

   I know that cp -f definitely *isn't* portable.  I forget where it
   misbehaved, but it was a bug report against one of my earlier packages.
   Unfortunately, it was for an old Makefile whose revision history I didn't
   save when I rewrote the package as a Perl module.  SunOS, maybe?

Yes, SunOS cp does not support -f.  SunOS mv, however, does.

SunOS cp supports -i, -p, -r.  I don't think -p or -r are portable.

It's possible to deduce why mv and cp are different with respect to
-f.  mv prompts by default before overwriting a read-only file.  cp
does not.  Therefore, mv requires a -f option, but cp does not.  mv
and cp behave differently with respect to read-only files because the
simplest form of cp can not overwrite a read-only file, but the
simplest form of mv can.  This is because cp opens the target for
write access, whereas mv simply calls link (or, in newer systems,
rename).

Ian