Re: how to write a script that recursively check files in a directory with md5sum

[John Summerfield]

Matthias Czapla wrote:
On Thu, Jul 15, 2004 at 07:14:30AM +0800, John Summerfield wrote:
 

find ~ -type f -exec cat {} \;
         

This fails because
cat doesn't check anything - it just copies all files to stdout
It doesn't handle files whose names contain spaces
       

Hu? I used cat solely for the purpose of showing how to execute
arbitrary commands recursively for each file in a directory tree.
How exactly does cat care about its argument containing spaces?
     

Since he specifically said he wants to use mdsum, it's clearer to use 
the program he said he wants to use.
   

Generally true but in this case the specific command executed by find
is irrelevant.
 

Try it and see what happens.
   

Ok:
<[EMAIL PROTECTED] ~/tmp>find a -type f -exec echo .{}. \;
.a/b  b/file.
.a/ b/ c c/file.
.a/bb  b  /file  with spaces.
.a/file with  spaces.
<[EMAIL PROTECTED] ~/tmp>find a -type f -exec md5sum {} \;
d41d8cd98f00b204e9800998ecf8427e  a/b  b/file
d41d8cd98f00b204e9800998ecf8427e  a/ b/ c c/file
d41d8cd98f00b204e9800998ecf8427e  a/bb  b  /file  with spaces
d41d8cd98f00b204e9800998ecf8427e  a/file with  spaces
Where's the problem?
 

The problem is that fragments of file names separated by spaces are 
indistinguishable from filenames separated by spaces.
   

This is only true when the command line is being split into words, e.g.
by the shell. find's '{}' parameter is given to the command literally
as one of the strings in argv[], it is *not* parsed for token delimiter
characters or anything.
 

<blush>
I don't use  -exec on find any more because it's slow. When you pipe the 
names into xargs as I do, then spaces cause the problem I described.

For slowness, consider this:
[EMAIL PROTECTED]:~$ find ~ -type f | wc -l
886076
[EMAIL PROTECTED]:~$
and this:
[EMAIL PROTECTED]:~$ find ~ -type f -print0 | xargs -0 | wc -l
3990
[EMAIL PROTECTED]:~$
--
Cheers
John
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