Correct syntax for executing commands with arguments in find -exec

Question

I have this line in a script that is supposed to be pruning old backups, except it throws an error that the target is a directory:

find $BACKUP_DIR* -mtime $RETENTION -exec rm {} \;  >> $MSG 2>&1

so I am trying to add the -rf to the rm command, but it's still not working [no errors!]

find $BACKUP_DIR* -mtime $RETENTION -exec "rm -rf" {} \;  >> $MSG 2>&1

What is the correct syntax for that command? I've tried double quotes, single quotes and backticks... do I have to escape the -rf somehow?

nope that was the first thing I tried. It doesn't work I'm assuming because it looks like an argument to the find command. — Sean Kimball
– Sean Kimball, Commented Nov 7, 2014 at 22:12
@SeanKimball Why do you say it doesn't work? what error message do you get? — gniourf_gniourf
– gniourf_gniourf, Commented Nov 7, 2014 at 22:13
The problem is trying to quote "rm -rf", that causes the shell to pass that as a single token to find -exec which is interpreted as the name of the command, remove the quotes, tokens after -exec are interpreted as utility, followed by arguments, no further expansion or interpretation by the shell. — amdn
– amdn, Commented Nov 7, 2014 at 22:27

2 revs · Accepted Answer · 2014-11-07 22:32:03Z

4

I typically prefer the -0 xargs method:

find ... -print0 | xargs -0r rm -rf

This does, however only work with commands which take one or multiple arguments till the end of the line. But it is quite safe as it takes any binary junk in the file name and present it as nicely separated arguments. It also avoids having to remeber this {} syntax. It also reduces the number of child executions. The -r option is needed in the GNU variant to make sure it does not call the command if no match is found. For FreeBSD it is ignored (as it is the default).

In your case, there is also a -delete action for GNU find:

find ... -delete

If you insist on using the escape method, then it would be:

find ... -exec /bin/rm -rf "{}" \;

Or if using GNU find, you can be a bit more efficient with:

find ... -exec /bin/rm -rf "{}" +

And just to be sure, use -ok :)

touch test1 test2 test3
find . -type f -ok rm -rf "{}" +
"rm -rf ./test1 ./test2 ./test3"? y

And to answer your question: no you don't have to escape the commands options. If it does not work, your problem is somewhere else, must likely in the startdir & search pattern. Try without output redirection and using -print or -ok to debug.

edited Nov 7, 2014 at 22:32

community wiki

2 revs
eckes

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4 Comments

Jonathan Leffler Over a year ago

Note that POSIX find supports the + notation, which typically renders the GNU -print0 and -0 extensions to find and xargs unnecessary.

Jonathan Leffler Over a year ago

I'm curious: why did you make your answer community wiki?

eckes Over a year ago

@JonathanLeffler I typically do that, so people can improve it. Some even refuse to upvote (for whatver reasons) non-wiki answers. And, I do not have only positive experiences with this:)

Jonathan Leffler Over a year ago

People can improve a non-wiki answer, either by edit or by suggestion. Your answer is good; I'd quibble about the order of -print0 vs +, but that is quibbling, not a serious issue. You should have a little more confidence.

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