C how to use the function uname

Question

I should write a function to get some information about the system (the most important information is the the architecture). I found the function uname which can be used including sys/utsname.h. Well, though I googled and I read the documentation, I couldn't find any example of the function and I don't understand how to use uname. Anyone can explain me how to use it? it would be great if you can write an example, too. Thanks in advance.

When you say platform, what do you mean? x86 vs x64? Linux vs BSD? AMD vs Intel? — Billy ONeal, Aug 29 '10 at 19:51
sorry I didn't specified, I mean for istance i686, x86, x64... — En_t8, Aug 29 '10 at 19:56

score 28 · Answer 1 · answered Aug 29 '10 at 19:53

28

First, include the header:

#include <sys/utsname.h>

Then, define a utsname structure:

struct utsname unameData;

Then, call uname() with a pointer to the struct:

uname(&unameData); // Might check return value here (non-0 = failure)

After this, the struct will contain the info you want:

printf("%s", unameData.sysname);

http://opengroup.org/onlinepubs/007908775/xsh/sysutsname.h.html

answered Aug 29 '10 at 19:53

Amber

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Just remember to use `struct utsname` instead of `struct ustname` or you'll get a `error: storage size of ‘myVar’ isn’t known`. – vesperto Jun 01 '23 at 11:14

tupiniquim · Answer 2 · 2021-03-06T17:45:50.953

26

A fully working example is worth a thousand words. ;-)

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

int main(void) {

   struct utsname buffer;

   errno = 0;
   if (uname(&buffer) < 0) {
      perror("uname");
      exit(EXIT_FAILURE);
   }

   printf("system name = %s\n", buffer.sysname);
   printf("node name   = %s\n", buffer.nodename);
   printf("release     = %s\n", buffer.release);
   printf("version     = %s\n", buffer.version);
   printf("machine     = %s\n", buffer.machine);

   #ifdef _GNU_SOURCE
      printf("domain name = %s\n", buffer.domainname);
   #endif

   return EXIT_SUCCESS;
}

edited Mar 06 '21 at 17:45

answered Dec 24 '14 at 16:01

tupiniquim

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Should use `perror` on failure. No need to handle the `EFAULT` specially (it won't happen in your code, since `buffer` is a valid address of a local variable) – Basile Starynkevitch Dec 24 '14 at 17:24
1

Thanks Basile. In fact `perror` is better than `switch (errno)` and I've edited the post to reflect that. The code was explicitly handling `EFAULT` because I wrote it with teaching in mind, but indeed this particular example would never get there. – tupiniquim Feb 13 '15 at 19:12
2

uname() may return 0 in case of success, code has to be changed to `uname(&buffer) < 0` – Étienne Apr 17 '20 at 09:00
it would be even more valuable to see the output on various machines/distros. Weird that nobody does that even though they went through the trouble of creating the code. – Andrew Robinson Mar 11 '23 at 13:00

score 9 · Answer 3 · answered Aug 29 '10 at 19:54

From the documentation, it looks like you'd use it like so:

struct utsname my_uname;
if(uname(&my_uname) == -1)
   printf("uname call failed!");
else
   printf("System name: %s\nNodename:%s\nRelease:%s\nVersion:%s\nMachine:%s\n",
       my_uname.sysname, my_uname.nodename, my_uname.release,my_uname.version,my_uname.machine);

score 6 · Answer 4 · answered Aug 29 '10 at 19:52

The uname() function takes a pointer to the utsname structure that will store the result as input. Therefore, just make a temporary utsname instance, pass the address of it to uname, and read the content of this struct after the function succeed.

struct utsname retval;
if(uname(&retval) < 0) {     // <----
  perror("Failed to uname");
  // error handling...
} else {
  printf("System name = %s\n", retval.sysname);
  // print other info....
  // see http://www.opengroup.org/onlinepubs/009695399/basedefs/sys/utsname.h.html
  //   for other members...
}

C how to use the function uname

4 Answers4

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