How to get an IP address from network interfaces

[Alexander Zhirov]

On Thursday, 21 April 2022 at 07:20:30 UTC, dangbinghoo wrote:
> On Thursday, 21 April 2022 at 07:04:18 UTC, Alexander Zhirov 
> wrote:
>> I want to get the IP address of the network interface. There 
>> is both a wireless interface and a wired one. Is it possible, 
>> knowing the name of the network interface, to get its IP 
>> address?
>
> ```d
> 	import core.sys.posix.sys.ioctl;
> 	import core.sys.posix.arpa.inet;
> 	
> 	import core.stdc.string;
> 	import core.stdc.stdio;
> 	import core.stdc.errno;
> 	import core.sys.posix.stdio;
> 	import core.sys.posix.unistd;
> 	
> 	string ip;
>
> 	
> 	int get(string if_name)
> 	{
> 		int s = socket(AF_INET, SOCK_DGRAM, 0);
> 		if (s < 0) {
> 			fprintf(stderr, "Create socket failed!errno=%d", errno);
> 			return -1;
> 		}
> 	
> 		ifreq ifr;
> 		uint nIP, nNetmask, nBroadIP;
>
> 		strcpy(ifr.ifr_name.ptr, std.string.toStringz(if_name));
> 		try {
> 			if (ioctl(s, SIOCGIFHWADDR, &ifr) < 0) {
> 				return -2;
> 			}
> 		}
> 		catch (Exception e) {
> 			writeln("Error operation on netif " ~ if_name);
> 			return -2;
> 		}
> 		memcpy(macaddr.ptr, cast(char *)ifr.ifr_hwaddr.sa_data.ptr, 
> 6);
> 	
> 		if (ioctl(s, SIOCGIFADDR, &ifr) < 0) {
> 			nIP = 0;
> 		}
> 		else {
> 			nIP = *cast(uint*)(&ifr.ifr_broadaddr.sa_data[2]);
> 			ip = fromStringz(inet_ntoa(*cast(in_addr*)&nIP)).idup;
> 		}
>        }
>
> ```



Gives a lot of errors when compiling

```d
app.d(19): Error: function 
`std.stdio.makeGlobal!"core.stdc.stdio.stderr".makeGlobal` at 
/usr/include/dlang/dmd/std/stdio.d(5198) conflicts with variable 
`core.stdc.stdio.stderr` at 
/usr/include/dlang/dmd/core/stdc/stdio.d(927)
app.d(19): Error: function 
`core.stdc.stdio.fprintf(shared(_IO_FILE)* stream, scope 
const(char*) format, scope const ...)` is not callable using 
argument types `(void, string, int)`
app.d(19):        cannot pass argument `makeGlobal(StdFileHandle 
_iob)()` of type `void` to parameter `shared(_IO_FILE)* stream`
app.d(23): Error: undefined identifier `ifreq`
app.d(26): Error: undefined identifier `string` in package `std`
app.d(39): Error: undefined identifier `macaddr`
app.d(48): Error: undefined identifier `fromStringz`
```