27

I need to copy a /home/user folder from one hard disk to another one. It has 100,000 files and around 10G size.

I use

cp -r /origin /destination

sometimes I get some errors due to broken links, permissions and so on. So I fix the error, and need to start again the copy.

I wonder how could I tell the command "cp", once it tries to copy again, not to copy files again if they exist in the destination folder.

migrated from stackoverflow.com Mar 11 '10 at 16:51

This question came from our site for professional and enthusiast programmers.

  • 1
    Don't us cp. Use rsync instead. – William Pursell Mar 11 '10 at 16:08
19

cp -R -u -p /source /destination

The -u (or --update) flag does just this:

From the man page for cp:

-u, --update

copy only when the SOURCE file is newer than the destination file or when the destination file is missing

  • 6
    To literally only copy files that don't exist and not update existing ones, yes n | cp -i /source/* /destination 2>/dev/null – sventechie Nov 21 '13 at 20:14
  • 4
    -u, --update copy only when the SOURCE file is newer than the destination file or when the destination file is missing -u, --update copy only when the SOURCE file is newer than the destination file or when the destination file is missing -p same as --preserve=mode,ownership,timestamps --preserve[=ATTR_LIST] preserve the specified attributes (default: mode,ownership,time‐ stamps), if possible additional attributes: context, links, xattr, all – Covich Feb 16 '16 at 15:29
34

Just use cp -n <source> <dest>.

From man page:

-n, --no-clobber

do NOT overwrite an existing file (overrides a previous -i option)

  • 5
    This is the only true answer to the question. – sebix Mar 21 '17 at 18:19
18

rsync -aq /src /dest

Apart from only copying newer files, it will even only copy the newer parts of files if the file has changed. It's intended for copying over network links where you want to minimise the amount of data - but it also works great locally.

  • I can't add `` formatting to your post because it's only two characters. How would you feel about editing this and adding `` characters around your command? – culix Apr 24 '16 at 18:02
4

Look up the "-u" option for the cp command.

  • 2
    Disagree that using -u is a good idea. -u copies only when source is newer or destination is missing. Original poster's issue was caused by file copy breaking for whatever reason. OP would therefore have half-written file that wasn't updated when re-running the copy. That file might be important to someone! rsync solves this problem. – hazymat Dec 21 '13 at 21:47
2

All above answers are correct but if you are doing this recursively then

you should do:

 cp -rn SOURCE_PATH DESTINATION_PATH
1

You should be copying as root to maintain permissions/ownership

# cp -au

Also look at rsync

0

POSIX solution

Other answers use -u or -n options of cp. Neither of these is required by POSIX; nor is rsync from yet another answer; nor is yes used in one of the comments.

Still we can reproduce yes n with a while loop. This leads to the following POSIX solution:

while true; do echo n; done | cp -Ri /origin /destination 2>/dev/null
0

Use cp -rn <sourcedirname>/. <destdirname>

The r switch makes the copy recursive over the directories.

The n switch (long version no-clobber) ensures existing files are never over-written.

The '/.' after the sourcedirname ensures that it does not become a subdirectory under the destdirname instead of all contents of the former being copied to the latter.

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