How to emulate 'cp --update' behavior on Mac OS X?

Question

The GNU/Linux version of cp has a nice --update flag:

-u, --update copy only when the SOURCE file is newer than the destination file or when the destination file is missing

The Mac OS X version of cp lacks this flag.

What is the best way to get the behavior of cp --update by using built-in system command line programs? I want to avoid installing any extra tools (including the GNU version of cp).

Answer 1

rsync has an -u/--update option that works just like GNU cp:

$ rsync -u src dest

Answer 2

Also look at rsync's other options, which are probably what you actually want:

    -l, --links                 copy symlinks as symlinks
    -H, --hard-links            preserve hard links
    -p, --perms                 preserve permissions
        --executability         preserve executability
    -o, --owner                 preserve owner (super-user only)
    -g, --group                 preserve group
        --devices               preserve device files (super-user only)
        --specials              preserve special files
    -D                          same as --devices --specials
    -t, --times                 preserve times

    -a, --archive
          This is equivalent to -rlptgoD. It is a quick way of saying you want recursion 
          and want to preserve almost everything (with -H being a  notable  omission).   The
          only exception to the above equivalence is when --files-from is specified, in which 
          case -r  is not implied.

          Note that -a does not preserve hardlinks, because finding multiply-linked files is
          expensive.  You must separately specify -H.