The getaddrinfo() function is part of the POSIX standard API in support for using it as a function to resolve a DNS hostname and IP addresses from their human-readable text form into a format for the operating system’s networking API.

The reverse function is getnameinfo().

Example

The following example uses getaddrinfo() to get a result, then calls getnameinfo()<tt> to get the canonical name for the address. Normally, this will give back the original hostname, unless the particular address has multiple names, in which case the “canonical” name is returned.

#include <stdio.h>
#include <netdb.h>
#include <netinet/in.h>

int main()
{
    struct addrinfo *result;
    char hostname[NI_MAXHOST];
    int error;

    if (error = getaddrinfo("www.example.com", NULL, NULL, &result))
    {
        fprintf(stderr, "error using getaddrinfo: %s\n", gai_strerror(error));
    }

    if (result)
    {
        if (error = getnameinfo(result->ai_addr, sizeof(struct sockaddr), hostname, sizeof(hostname), NULL,0,0))
        {
            fprintf(stderr, "error using getnameinfo: %s\n", gai_strerror(error));
        }
    }
}

See also

• Hostname
• Network address
• Domain name system