Merging folders with mv?

Question

If I use mv to move a folder called "folder" to a directory that already contains "folder" will they merge or will it be replaced?

Answer 1

mv cannot merge or overwrite directories, it will fail with the message "mv: cannot move 'a' to 'b': Directory not empty", even when you're using the --force option.

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You can work around this using other tools (like rsync, find, or even cp), but you need to carefully consider the implications:

• rsync can merge the contents of one directory into another (ideally with the --remove-source-files¹ option to safely delete only those source files that were transferred successfully, and with the usual permission/ownership/time preservation option -a if you wish)
  … but this is a full copy operation, and can therefore be very disk-intensive.
• You can use find to sequentially recreate the source directory structure at the target, then individually move the actual files
  … but this has to recurse through the source multiple times and can encounter race conditions (new directories being created at the source during the multi-step process)
• cp can create hard links (simply put, additional pointers to the same existing file), which creates a result very similar to a merging mv (and is very IO-efficient since only pointers are created and no actual data has to be copied)
  … but this again suffers from a possible race condition (new files at the source being deleted even though they weren't copied in the previous step)

Which of these workarounds (if any) is appropriate will very much depend on your specific use case.
As always, think before you execute any of these commands, and have backups.

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_{1: Note that rsync --remove-source-files won't delete any directories, so you will have to do something like find -type d -empty -delete afterwards to get rid of the empty source directory tree.}

Answer 2

rsync -av /source/ /destination/
(after checking)
rm -rf /source/

Answer 3

You can use the -l option of the cp command, which creates hard links of files on the same filesystem instead of full-data copies. The following command copies the folder source/folder to a parent folder (destination) which already contains a directory with the name folder.

cp -rl source/folder destination
rm -r source/folder

You may also want to use the -P (--no-dereference - do not de-reference symbolic links) or -a (--archive - preserve all metadata, also includes -P option), depending on your needs.

Answer 4

I'd recommend these four steps:

cd ${SOURCE}; 
find . -type d -exec mkdir -p ${DEST}/\{} \; 
find . -type f -exec mv \{} ${DEST}/\{} \; 
find . -type d -empty -delete

or better yet, here's a script that implements semantics similar to mv:

#!/bin/bash

DEST="${@:${#@}}"
ABS_DEST="$(cd "$(dirname "$DEST")"; pwd)/$(basename "$DEST")"

for SRC in ${@:1:$((${#@} -1))}; do   (
    cd "$SRC";
    find . -type d -exec mkdir -p "${ABS_DEST}"/\{} \;
    find . -type f -exec mv \{} "${ABS_DEST}"/\{} \;
    find . -type d -empty -delete
) done

Answer 5

Here is a way that will merge the directories. It is much faster than rsync since it just renames the files instead of copying them and then deleting them.

cd source; find -type f -print0 | xargs -0 -n 1 -I {} mv '{}' 'dest/{}'

Answer 6

One way to accomplish this would be to use:

mv folder/* directory/folder/
rmdir folder

As long as no two files have the same name in folder and directory/folder, you will achieve the same result i.e. merging.

Answer 7

Here is a script that worked for me. I prefer mv over rsync, so I use Jewel and Jonathan Mayer's solutions.

#!/bin/bash

# usage source1 .. sourceN dest

length=$(($#-1))
sources=${@:1:$length}
DEST=$(readlink -f ${!#})
for SRC in $sources; do
    pushd $SRC;
    find . -type d -exec mkdir -p ${DEST}/{} \;
    find . -type f -exec mv {} ${DEST}/{} \;
    find . -type d -empty -delete
    popd
done

Answer 8

It is not a good idea to use commands like cp or rsync. For large files, it will take a long time. mv is much faster since it only update the inodes without copying the files physically. A better option is to use the file manager of your operating system. For Opensuse, there is a file manager called Konquerer. It can move files without actually copying them. It has "cut and paste" function like in Windows. Just select all the sub-directories in directory A. Right click and "move into" directory B which may contain sub-directories with the same names. It will merge them. There are also options whether you want to overwrite or rename files with the same name.

Answer 9

For the purest copies, I use the tar (-)B blockread copy method.

example, from source path:

tar cBf - <sourcefolder> | (cd /your/target/folder ; tar xBf -)

this creates an exact copy of the source tree, WITH the owner and permissions intact. And if the target folder exists, the data will be merged. Only files that are already existing will be overwritten.

When the copy action is successful, you can remove the source (rm -rf <source>). Of course this is not an exact move: the data will be copied, until you remove the source.

As option you can be verbose (display on screen the file being copied), with -v: tar cBvf -

• c: create
• B: read full block (for pipe read)
• v: verbose
• f: file to write
• x: extract
• -: stdout/stdin

sourcefolder can also be * (for anything in current folder)