Ubuntu – What’s the missing argument to -exec

bashcommand linefindsyntax

I use the following command to clear a directory, of files and directories over 30 days old, and move them to an archive directory which I can delete after a few weeks if nobody asks for their files back. The target directory has subdirectories by user name, so will the archive directory.

This is the command I use:

find /path/to/directory/username/ -mtime +30 -exec mv "{}" /path/to/archive/username/ \;

I suggested a modified version of this to answer a question on ask ubuntu, another user edited the code to change the end of line \; for + as it's faster(and more correct?). See here

However, using + in this way works if the -exec command is ls -lh but not in the actual command that I use. If I try it with + I get an error message:

find: missing argument to '-exec'

I don't understand why it's behaving this way, or what the correct command would be. Please don't just post a command correction, I'd like to understand rather than just follow a suggestion blindly.

Best Answer

The user in that post may said that the + sign at the end of a -exec command is faster, but not why.

Lets assume the find command return the following files:

/path/to/file1
/path/to/file2
/path/to/file3

The normal -exec command (-exec command {} \;) runs once for each matching file. For example: 

find ... -exec mv {} /target/ \;

Executes:

mv /path/to/file1 /target/
mv /path/to/file2 /target/
mv /path/to/file3 /target/

If you use the + sign (-exec command {} +) the command is build by adding multiple matched files at the end of the command. For example:

find ... -exec mv -t /target/ {} +

Executes:

mv -t /target/ /path/to/file1 /path/to/file2 /path/to/file3

To use the + flag correctly the argument to process must be at the end of the command, not in the middle. That's why find trows missing argument to '-exec' in your example; it misses the closing {}.

Related Question