How can I copy a (big) directory over another changing only the files that differ?

Question

I have directory a and directory b. They are big. b is almost identical to a. "almost" means that 4-5 files differ, and I don't know which they are. I want to copy b over a, but only the files that differ. i'm in bash.

(no, I can't simply delete a and replace it with b, because 1) a is version-controlled 2) a full copy (or a mv) would take too much. I want to copy only the files that differ).

Solution 1

You can use rsync to do this, the command I use is rsync -tr "folder to copy from" "folder to copy to"

e.g. rsync -tr /home/me/stuff/* /home/me/otherstuff/

Solution 2

It is also possible to do this with good old cp:

Thanks to srcspider for reminding me to use -T!

cp -ruT old-dir new-dir

Solution 3

You can diff the 2 directories.

diff -r dir1 dir2

it will show you the list of files that are differnet

Solution 4

Another good option is Unison (http://www.cis.upenn.edu/~bcpierce/unison/), particularly if there isn't really a "source" and a "destination". Each directory is a root and Unison syncs them and keeps metadata for future syncs. It offers both a command-line and a GUI option that can easily be scheduled via cron as well.

I use it to make a backup of my Dropbox to my local NAS appliance which can't run a Dropbox client.

Solution 5

It CAN be done with good ol' cp, though with a slightly different format than stated above. Here's how I did it:

cp -ru --target-directory="destination_path" source_path/*

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Comments

[Jjames]

Is rsync an option?

[Shadarath]

It is, but I don't know much about rsync.

[Tog]

+1 I get so used to synching across machines I forget the elegant ways.

[Shadarath]

does not work for me :(

[Keith]

That's actually good gnu cp. ;-)

[Jean-François Beauchamp]

On OS X, the -u option does not exist. I simply used cp -r old-dir new-dir, since I did not have to compare dates.

[srcspider]

Does not work. I am not sure if this is some name convention but cp -ru folder-A folder-B will simply copy folder-A inside folder-B not copy contents of A inside B and overwrite, which would be the desired effect.

[srcspider]

@new123456 -T is not documented in --help for me can you paste the description in the answer please. :)

[new123456]

@srcspider You must not be using GNU cp, then - on my machine, cp from coreutils 8.13 mentions the -T flag in the help. The online documentation describing what exactly -T does is on GNU's site.

[srcspider]

@new123456 Yeah it seems the windows git bash version doesn't have it; I'm on a unix box now and it's in the docs. Is there some other command that will copy the files from A to B and overwrite?

[Arvind K.]

BEWARE of this command. It will delete all the files which wont differ. I ran it and LOST almost everything!!

[Tog]

@Arvind I don't know what command you used that caused you to lose your data but it wasn't rsync -tr. Read the man page.