Integer to IP Address - C

c string ip-address
Kris Richards picture Kris Richards · Nov 5, 2009 · Viewed 116.6k times · Source

I'm preparing for a quiz, and I have a strong suspicion I may be tasked with implementing such a function. Basically, given an IP address in network notation, how can we get that from a 32 bit integer into a string in it's dotted decimal notation (something like 155.247.182.83)...? Obviously we can't be using any type of inet functions either...I'm stumped!

Answer

Rose Perrone picture Rose Perrone · Oct 7, 2013

You actually can use an inet function. Observe.

main.c:

#include <arpa/inet.h>

main() {
    uint32_t ip = 2110443574;
    struct in_addr ip_addr;
    ip_addr.s_addr = ip;
    printf("The IP address is %s\n", inet_ntoa(ip_addr));
}

The results of gcc main.c -ansi; ./a.out is

The IP address is 54.208.202.125

Note that a commenter said this does not work on Windows.

Related questions

How do I concatenate const/literal strings in C?

I'm working in C, and I have to concatenate a few things. Right now I have this: message = strcat("TEXT ", var); message2 = strcat(strcat("TEXT ", foo), strcat(" TEXT ", bar)); Now if you have experience in C I'm sure you realize …

Read More
How do I create an array of strings in C?

I am trying to create an array of strings in C. If I use this code: char (*a[2])[14]; a[0]="blah"; a[1]="hmm"; gcc gives me "warning: assignment from incompatible pointer type". What is the correct way to do this? edit: …

Read More
How to convert a string to integer in C?

I am trying to find out if there is an alternative way of converting string to integer in C. I regularly pattern the following in my code. char s[] = "45"; int num = atoi(s); So, is there a better way or …

Read More