UNIX for Dummies Questions & Answers

Hi,

What is the difference between these two?

Code:

find /some_dir -type f -exec chmod 070 {} \;

and

Code:

chmod 070 `find /some_dir -type f`

Thanks

The command above will execute one chmod command for every file it finds. In theory less efficient because of the overhead of starting a new process for each file.

The second command invokes one chmod process to set the permissions on all of the files that are discovered by find. The biggest potential problem with this command is that the number of files found could cause the command argument limit to be exceeded. If you are wanting to minimise the number of chmod processes that are started, this would be the best method:

Code:

find /path -type f | xargs chmod 0755

The xargs command will invoke chmod with the output from find, ensuring that the maximum argument limit isn't exceeded. If it has to, it will invoke chmod more than once, but you won't have a 1:1 ratio of chmod processes to files found.

What's the maximum limit for the argument limit?
How to check in every OS?
Thanks

You will check ARG MAX.

Code:

getconf ARG_MAX

In addition to possible problems with the command line being too long, this method will fail if any filename contains a space character.


@pandeesh
Please stop hijacking threads. There is no general answer to your specific question or to any question referring to "any OS".

Great point; the xargs example I posted will have the same issue unless something like this is used:

Code:

find . |sed 's/^/"/; s/$/"/' |xargs chmod 755