What is the '+' in find command for?

Question

I have some times come across the use of trailing + while using unix commands like find.

Example from SO post -

find . -exec touch -t 201007162310.00 {} +

Please help me understand the use of this.

Answer 1

From man find:

-exec command {} +

This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of {} is allowed within the command. The command is executed in the starting directory.

For example with find -exec touch -t 201007162310.00 {} +, if the find command without the -exec gives you the files 1.txt, 2.txt and 3.txt, it will execute:

touch -t 201007162310.00 1.txt
touch -t 201007162310.00 2.txt
touch -t 201007162310.00 3.txt

with -exec ... {} \;, and

touch -t 201007162310.00 1.txt 2.txt 3.txt

with -exec ... {} +.

The latter version is faster due to a (much) smaller number of new processes needed yet it is less portable (not all find implementations support it). And of course, if the command you try to -exec doesn't support receiving multiple files as arguments, it won't work.