getnetbyaddr_r - Linux

Overview

The getnetbyaddr_r command returns the name of the network corresponding to the specified addr. It is commonly used in networking applications to identify and access network resources.

Syntax

getnetbyaddr_r(addr, buf, buflen, result, h_errnop)

Options/Flags

Required Arguments:

• addr: the address to get the network name for

Buffers:

• buf: a pointer to a buffer to store the network name
• buflen: the size of the buffer

Return Values:

• result: a pointer to the resulting network entry structure or NULL if not found
• h_errnop: a pointer to an integer that contains the error code

Examples

Simple example:

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

int main() {
    struct hostent *result;
    char buf[256];
    int h_errnop;

    if (getnetbyaddr_r("192.168.1.1", buf, sizeof(buf), &result, &h_errnop) != 0) {
        fprintf(stderr, "Error: %s\n", hstrerror(h_errnop));
        return 1;
    }

    printf("Network name: %s\n", result->h_name);

    return 0;
}

Complex example:

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

int main() {
    char addr[] = "192.168.1.0";
    struct netent *result;
    char buf[256];
    int h_errnop;

    while ((result = getnetbyaddr_r(addr, buf, sizeof(buf), &h_errnop)) != NULL) {
        printf("Network: %s (%s)\n", result->n_name, result->n_addr);
        addr += 4;
    }

    return 0;
}

Common Issues

• h_errnop: will be set to one of the following error codes if an error occurs:

  • NO_DATA: no network entry exists for the specified address
  • TRY_AGAIN: a temporary error occurred and the operation should be retried

Integration

getnetbyaddr_r can be combined with other networking commands such as gethostbyname_r to resolve IP addresses and hostnames.

Related Commands

• gethostbyname_r: resolves a hostname to an IP address
• getservbyname_r: resolves a service name to a port number