What's the missing argument to -exec?

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 {}.

The user explained their edit....

...using this link. I think basically instead of using multiple commands, it sends all the filenames to one command instance, to speed things up. Here is a example from here:

Using -exec with a semicolon (find . -exec ls '{}' \;), will execute

ls file1
ls file2
ls file3

But if you use a plus sign instead (find . -exec ls '{}' \+), all filenames will be passed as arguments to a single command:

ls file1 file2 file3

There are other forms available using ; and + as well (from here:)

Therefore the following example syntax is allowed for find command:

find . -exec echo {} \;
find . -exec echo {} ';'
find . -exec echo {} ";"
find . -exec echo {} \+
find . -exec echo {} +

HOWEVER, I'm not sure this will work with the move command anyway, as it's syntax is mv [OPTION]... SOURCE DEST, unless the -t option or similar is used. However it should work with ls with no extra options etc as they can understand when multiple filenames are given. The + may also need to be escaped (i.e. \+)