freeaddrinfo - Linux

Overview

freeaddrinfo is a Linux command used to free the linked list of linked addrinfo structures returned by getaddrinfo(3). This command is commonly used as part of network programming in C and C++ to release memory allocated during address resolution.

Syntax

freeaddrinfo(struct addrinfo *res)

Parameters

| Parameter | Description |
|—|—|
| res | Pointer to the linked list of addrinfo structures to be freed. |

Options/Flags

None.

Examples

Simple Usage:

#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>

int main() {
    struct addrinfo hints, *res;
    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    int err = getaddrinfo(NULL, "8080", &hints, &res);
    if (err != 0) {
        perror("getaddrinfo failed");
        exit(EXIT_FAILURE);
    }

    freeaddrinfo(res);
    return 0;
}

Advanced Usage:

#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>

int main() {
    struct addrinfo hints, *res, *ptr;
    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_family = AF_INET6;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_CANONNAME;

    int err = getaddrinfo("example.com", "8080", &hints, &res);
    if (err != 0) {
        perror("getaddrinfo failed");
        exit(EXIT_FAILURE);
    }

    ptr = res;
    while (ptr != NULL) {
        printf("Host: %s\n", ptr->ai_canonname);
        printf("Address: %s\n", ptr->ai_addr->sa_data);
        ptr = ptr->ai_next;
    }

    freeaddrinfo(res);
    return 0;
}

Common Issues

Memory Leak:

If freeaddrinfo is not called after a successful call to getaddrinfo(3), it can result in a memory leak.

Solution:

Always call freeaddrinfo to release the memory allocated by getaddrinfo(3).

Integration

Combining with getaddrinfo(3):

freeaddrinfo is typically used in conjunction with getaddrinfo(3) to resolve hostnames and IP addresses.

Using with other commands:

freeaddrinfo can be used with other commands that require addrinfo structures, such as bind(2), connect(2), and accept(2).

Related Commands

• getaddrinfo(3)
• getnameinfo(3)
• gai_strerror(3)