getnetbyname_r - Linux

Overview

getnetbyname_r is a C library function that retrieves a network entry from the network database. It is typically used to obtain information about a specific network, such as its address, netmask, and gateway.

Syntax

int getnetbyname_r(const char *name, struct netent *result_buf, char *buffer, size_t buflen, struct netent **result);

Parameters:

  • name: The name of the network to retrieve. This is typically a string representing a hostname or an IP address.
  • result_buf: A pointer to a struct netent structure to store the retrieved network information.
  • buffer: A pointer to a memory buffer to store the retrieved network name.
  • buflen: The size of the memory buffer provided in buffer.
  • result: A pointer to a struct netent** that will be set to point to the retrieved network information.

Options/Flags

There are no options or flags available for getnetbyname_r.

Examples

Simple Example:

#include <netdb.h>

int main() {
    struct netent *netinfo;
    char buffer[1024];

    if (getnetbyname_r("example.com", &netinfo, buffer, sizeof(buffer), &result) == 0) {
        printf("Retrieved network info for example.com:\n");
        printf("Name: %s\n", netinfo->n_name);
        printf("Address family: %d\n", netinfo->n_addrtype);
        printf("Address: %s\n", inet_ntoa(netinfo->n_net));
    } else {
        perror("Error retrieving network info");
    }

    return 0;
}

Common Issues

One common issue that can occur when using getnetbyname_r is that the provided memory buffer (buffer) may not be large enough to store the retrieved network name. If this occurs, the function will return a -1 error and set errno to ERANGE. To resolve this issue, increase the size of the memory buffer and call the function again.

Integration

getnetbyname_r can be used in conjunction with other Linux commands or tools to configure and manage network settings. For example, it can be used with the ifconfig command to set the IP address and netmask of a network interface.

Related Commands

  • getnetbyaddr_r: Retrieves a network entry by network address.
  • gethostbyname_r: Retrieves a host entry by hostname.
  • gethostbyaddr_r: Retrieves a host entry by IP address.