There are various ways for listing the network interfaces while programming in C, The below code sample should be straight forward & list them all.


#include<stdio.h>
#include<net/if.h>
#include<string.h>

int main(int argc, char *argv[]){
    // Initializing Some Variables
    unsigned int max_interfaces = 255;
    char ifname[IFNAMSIZ];
    char old_ifname[IFNAMSIZ];

    for (unsigned int if_id=0; if_id<max_interfaces; if_id++) {
        if_indextoname(if_id, ifname);
        if  (ifname[0] == '\0'){
            continue;
        }   
        // Breaking out when the last interface name starts repeating
        else if (strcmp(ifname, old_ifname) == 0){
            break;
        }
        // Printing the interace id and name in stdout & storing the current value as a reference for the next iteration
        else {
            printf("%d: %s\n", if_id, ifname);
            snprintf(old_ifname, sizeof(old_ifname), "%s", ifname);
        }   
    }

    return 0;
}

This code is compiled & executed on linux o a recent kernel version, Please feel free to test it on other systems.

example:


user@pc$ gcc list_interfaces.c -o list_interfaces 
user@pc$ ./list_interfaces 
0: abc
1: lo
2: wlp6s0
3: enp2s0
4: docker0
5: testnet
6: vboxnet0
7: vboxnet1
8: vboxnet2
9: vboxnet3
10: eth_dummy

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