How do you copy directories in Linux in these situations using cp?

Question

Situation 1

How do I copy /home/src/somedir to /dest/ such that the path always ends up as /dest/somedir, regardless of whether /dest/somedir already exists?

I want to avoid ending up with /dest/somedir/somedir.

Situation 2

How do I copy everything inside /home/src/somedir to /dest/ such that /dest/somedir isn't created and is ignored if it already exists?

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Are there rules about the trailing slashes I can use? I thought ending with a trailing slash meant always copy the contents only but it still often goes wrong for me.

Answer 1

cp will always copy the file(s) at the start of the command to the file or directory at the end of the command. The slash doesn't really do much to the arguments, unless the argument is a symlink to a directory. Then having the slash will treat it like a directory while omitting the slash will copy the link itself.

Assuming you want recursively copy any subdirectories in your examples you'd do them like:

cp -r /home/src/somedir /dest

and

cp -r /home/src/somedir/* /dest

The first gets the directory /home/src/somedir and will copy that argument, the directory itself and all the contents of it, to the last arg, /dest. It will create the somedir directory in /dest if needed and use it if it already exists.

The second addes * to the end of the first argument, which the shell will expand to be every file that does not start with . in /home/src/somedir and will copy all of those files and directories to /dest without regard to what's already there (except some flags to cp will make it prompt to overwrite files that will have the same in in the destination as an existing file).

As the comments to this answer have pointed out, there are problems using * to grab all the files in the directory. One alternative would be to use tar to do the copy for you

tar -c -C /home/src/somedir . | tar -x -C /dest

this will create a tar file of somedir without the leading path by using -C to switch to that directory first. By default tar will print to stdout which we will then pipe to another tar to extract it switching into the desired /dest directory first. This will also preserve lots of file attributes, which cp can do as well.

Answer 2

How do I copy /home/src/somedir to /dest/ such that the path always ends up as /dest/somedir, regardless of whether /dest/somedir already exists?

cp -rv /home/src/somedir /dest

We are copying «somedir» to «/dest», so we end up with «/dest/somedir»

How do I copy everything inside /home/src/somedir to /dest/ such that /dest/somedir isn't created and is ignored if it already exists?

cp -rv /home/src/somedir/* /dest

We are copying «all files in somedir» (somedir/*) to «/dest»

Caveat: somedir/* doesn't include hidden files (those beginning with a dot).

The final slashes don't affect the process. You may be confusing cp with rsync, where a trailing slash means “copy the contents, not the folder”.