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Old 04-13-2011, 06:50 AM   #1
MarcosPauloBR
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Question How to get the Number of Cores using C


Hi people!

Anybody knows How can I get the number of cores of a machine?

I know that I can use POPEN and get the stream of this:
Code:
grep -i 'processor' /proc/cpuinfo | wc -l
But, I think that a simple method to do this.

Can anybody say to me??

Thanks!!
 
Old 04-13-2011, 08:16 AM   #2
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You could also just count the number of directories in /sys/devices/system/cpu/.

EDIT: well, the number of directories named cpu* in /sys/devices/system/cpu/.

Last edited by dugan; 04-13-2011 at 08:35 AM.
 
Old 04-13-2011, 08:31 AM   #3
MarcosPauloBR
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Thanks dugan!

But, with this ideia I will need a POPEN again:

ls /sys/devices/system/cpu/ | grep [0-9] | wc -l

There isn't a C header to handle this question?

Thanks!!
 
Old 04-13-2011, 08:37 AM   #4
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You don't need a popen to list subdirectories, open files, or count lines.

http://www.gnu.org/s/libc/manual/htm...stem-Interface

Last edited by dugan; 04-13-2011 at 08:43 AM.
 
Old 04-13-2011, 09:56 AM   #5
MarcosPauloBR
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So, I will make a function who receives a string with the path of the Folder, and list this to me...

But, I think my method of POPEN its more easy for handle than this opendir and dirent...


Dugan, thanks for this help!
 
Old 04-13-2011, 10:03 AM   #6
MTK358
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Quote:
Originally Posted by MarcosPauloBR View Post
But, I think my method of POPEN its more easy for handle than this opendir and dirent...
What does "it's more easy for handle" mean?

Also, in case you mean you would rather use popen(), don't. It's really a bad idea.
 
Old 04-13-2011, 10:16 AM   #7
MarcosPauloBR
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MTK358,

On my OPEPN I do a ls in the folder that I need.

With this stream I make a fgets, and while has a entry I call a function to work on this file.

On this case, I think its more "directly" to take one-by-one the names of the files, and I don't need to create any pointer and don't create any Struct.

Because of this I say "its more easy for handle" =P

I think when I begin to make a ls with the libc method, I will change my mind.

=D
 
Old 04-13-2011, 10:21 AM   #8
MTK358
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It's just that it doesn't seem like a good idea on relying on the system having a certain shell or utilities installed. And ls itself is written in C, and uses opendir(), etc.
 
Old 04-13-2011, 10:25 AM   #9
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So, you change my mind =D

I agree with your idea of rely on the host tools!

As I said, I will change my code and make a function to list whatever folder that I need!

Thanks for your help MTK358!
 
Old 04-13-2011, 04:14 PM   #10
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Well I think doing it in C is pretty.

Code:
numofcpus = sysconf(_SC_NPROCESSORS_ONLN); // Get the number of logical CPUs.
You can use sysconf() to get all kinds of configuration stuff.
http://www.gnu.org/s/libc/manual/htm...ts-for-Sysconf
 
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Old 04-14-2011, 09:54 AM   #11
MarcosPauloBR
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yaplej, its this exactly what I want!

I knew there is a simple method to get the number of cores on C!

Thanks for your help!
 
  


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