CODEWITHSUNDEEP
clinuxbash
user3574984
user3574984

Reputation: 453

Get Linux system information in C

I have to check Linux system information. I can execute system commands in C, but doing so I create a new process for every one, which is pretty expensive. I was wondering if there is a way to obtain system information without being forced to execute a shell command. I've been looking around for a while and I found nothing. Actually, I'm not even sure if it's more convenient to execute commands via Bash calling them from my C program or find a way to accomplish the tasks using only C.

Upvotes: 4

Views: 10945

Answers (3)

vmemmap
vmemmap

Reputation: 531

You can also use the sys/utsname.h header file to get the kernel version, hostname, operating system, machine hardware name, etc. More about sys/utsname.h is here. This is an example of getting the current kernel release.

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

int main(int argc, char const *argv[])
{
    struct utsname buff;
    printf("Kernel Release = %s\n", buff.release); // kernel release
    
    return 0;
}

This is the same as using the uname command. You can also use the -a option which stands for all information.

uname -r # -r stands for kernel release

Upvotes: 0

NlightNFotis
NlightNFotis

Reputation: 9803

A presumably less known (and more complicated) way to do that, is that you can also use the api interface to sysctl. To use it under Linux, you need to #include <unistd.h>, #include <linux/sysctl.h>. A code example of that is available in the man page:

#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <linux/sysctl.h>

int _sysctl(struct __sysctl_args *args );

#define OSNAMESZ 100

int
main(void)
{
    struct __sysctl_args args;
    char osname[OSNAMESZ];
    size_t osnamelth;
    int name[] = { CTL_KERN, KERN_OSTYPE };

   memset(&args, 0, sizeof(struct __sysctl_args));
    args.name = name;
    args.nlen = sizeof(name)/sizeof(name[0]);
    args.oldval = osname;
    args.oldlenp = &osnamelth;

   osnamelth = sizeof(osname);

   if (syscall(SYS__sysctl, &args) == -1) {
        perror("_sysctl");
        exit(EXIT_FAILURE);
    }
    printf("This machine is running %*s\n", osnamelth, osname);
    exit(EXIT_SUCCESS);
}

However, the man page linked also notes:

Glibc does not provide a wrapper for this system call; call it using syscall(2). Or rather... don't call it: use of this system call has long been discouraged, and it is so unloved that it is likely to disappear in a future kernel version. Since Linux 2.6.24, uses of this system call result in warnings in the kernel log. Remove it from your programs now; use the /proc/sys interface instead.

This system call is available only if the kernel was configured with the CONFIG_SYSCTL_SYSCALL option.

Please keep in mind that anything you can do with sysctl(), you can also just read() from /proc/sys. Also note that I do understand that the usefulness of that syscall is questionable, I just put it here for reference.

Upvotes: 3

Tom van der Woerdt
Tom van der Woerdt

Reputation: 29985

Linux exposes a lot of information under /proc. You can read the data from there. For example, fopen the file at /proc/cpuinfo and read its contents.

Upvotes: 7

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