how can I get the processor ID of the current process in C in Linux?

Question

I'm writing a program that needs to know what logical processor it's running on.

This question tells me how to do it in assembly, while this question tells me how to use this code in assembly without translating it to AT&T syntax.

Is there an easier way to do this using existing Linux system calls or library functions, or is it necessary for me to reinvent the wheel?

You could get that info but I'm not sure how long that info would be good as you could easily have that process rescheduled and run on another core at any time. — Jesus Ramos, Feb 20 '12 at 09:25
The question you refer to doesn't do what you want. It tells you how many CPUs there are, not which CPU you're running on. — ugoren, Feb 20 '12 at 09:54
follow this link: https://stackoverflow.com/questions/6491566/getting-the-machine-serial-number-and-cpu-id-using-c-c-in-linux — Hossein, Oct 23 '17 at 22:32
@HosseinBobarshad: That's a different thing entirely. My question is about the logical processor ID of the logical processor that the thread is running on, while the question you pointed me to is about the model of the processor, and perhaps its serial number. — Nathan Fellman, Oct 24 '17 at 10:37

score 9 · Answer 1 · answered Feb 20 '12 at 09:27

9

There's the linux specific getcpu call.

answered Feb 20 '12 at 09:27

abyx

69,862
18
95
117

3

Note that it gives you the cpu at the time of the call. The next instruction, your thread might be on another CPU. – ugoren Feb 20 '12 at 09:52
2

@ugoren of course! :) unless one uses `sched_setaffinity` http://linux.die.net/man/2/sched_setaffinity – abyx Feb 20 '12 at 11:12
Note that `getcpu` may be implemented in userspace (rather than as a syscall) via vdso, so it's possibly less expensive than you would expect. – R.. GitHub STOP HELPING ICE Feb 20 '12 at 15:56
And glibc has wrapper for this called `sched_getcpu`: https://stackoverflow.com/a/10256090/895245 – Ciro Santilli OurBigBook.com Oct 24 '19 at 13:16

score 7 · Answer 2 · edited Oct 24 '19 at 13:15

7

Tou can see sched_getcpu(). This glibc C function calls the getcpu Linux system call.

edited Oct 24 '19 at 13:15

Ciro Santilli OurBigBook.com

347,512
102
1,199
985

answered Apr 21 '12 at 04:05

onesuper

196
2
7

Minimal runnable example demonstrating interaction with `sched_setaffinity`: https://stackoverflow.com/questions/280909/how-to-set-cpu-affinity-for-a-process-from-c-or-c-in-linux/54478296#54478296 – Ciro Santilli OurBigBook.com Oct 24 '19 at 13:15

score -2 · Answer 3 · answered Feb 20 '12 at 09:29

Try this , i am not sure that what you want is this

#include<stdio.h>
#include<sys/utsname.h>

int main()
{

char hostname[1024];
struct utsname userinfo;
if(uname(&userinfo)>=0)
{
  printf("\n***** System Details ******\n");
  printf("System Name    : %s\n",userinfo.sysname);
  printf("System Node    : %s\n",userinfo.nodename);
  printf("System Release : %s\n",userinfo.release);
  printf("System Version : %s\n",userinfo.version);
  printf("System Machine : %s\n",userinfo.machine);
}
else
 printf("\nSystem details fetch failed..\n");



if(gethostname(&hostname,1024)==0)
{
  printf("Hostname : %s\n",hostname);
}
else
 printf("\nHostname details fetch failed..\n");

return 0;
}

That will give me the IP for the machine. I'm looking for the id of the core in the CPU that my process is running in. — Nathan Fellman, Feb 20 '12 at 20:53
is there any way to get the CPU ID or other kind hardware address? Specially for iPhone? — karim, May 03 '13 at 09:29

how can I get the processor ID of the current process in C in Linux?

3 Answers3

Linked