Why | doesn't work with find?

Question

Why does the following command aiming to remove recursively all .svn folders

   find . -name ".svn" | rm -rfv

doesn't work ?

I know the find command provides the -exec option to solve this issue but I just want to understand what is happening there.

score 12 · Accepted Answer · answered Jan 03 '11 at 09:19

12

In your example, the results from find are passed to rm's STDIN. rm doesn't expect its arguments in STDIN, though.

Here is an example how input redirecting works.

answered Jan 03 '11 at 09:19

Linus Kleen

Finally! Someone actually answers the question! – T.J. Crowder Jan 03 '11 at 09:21
Each reply answers the why, although some are a bit cryptic. – reinierpost Jan 03 '11 at 09:22

score 2 · Answer 2 · answered Jan 03 '11 at 09:20

2

rm does not read file names from standard input, so any data piped to it is ignored.

The only thing it uses standard input for is checking whether it's a terminal, so it can determine whether to prompt.

answered Jan 03 '11 at 09:20

Matthew Flaschen

score 1 · Answer 3 · answered Jan 03 '11 at 09:19

1

It doesn't work because rm does not accept a list of file names on its standard input stream.

Just for reference, the safest way to handle this in the case of directories that might contain spaces is:

find . -name .svn -exec rm -frv {} \;

Or, if you are shooting for speed:

find . -name .svn -print0 | xargs -0 rm -frv

answered Jan 03 '11 at 09:19

cdhowie

1

And if you read the **rest** of the question: *"I know the `find` command provides the `-exec` option to solve this issue but I just want to understand what is happening there."*. **Edit**: Okay, now you've edited enough to deal with it. – T.J. Crowder Jan 03 '11 at 09:20
1

I would expect (without testing) that `-exec rm -frv {} +` is fastest, since it has the fewest processes. – Matthew Flaschen Jan 03 '11 at 09:23

score 1 · Answer 4 · answered Jan 03 '11 at 09:22

1

find do works with | ( for example find ~ -name .svn | grep "a") but the problem is with rm

answered Jan 03 '11 at 09:22

Martin Trigaux

Exactly. That's because `grep` *expects* input from STDIN, whereas `rm` ignores anything piped to it and wants parameters. – Linus Kleen Jan 03 '11 at 09:27

score 0 · Answer 5 · edited May 23 '17 at 12:18

0

This question is similar to this other answered question. Hope this helps.

edited May 23 '17 at 12:18

Community

answered Jan 03 '11 at 09:24

dave

5 Answers5