C Program to display hostname and IP address

There are many ways to find Hostname and IP address of a local machine. Here is a simple method to find hostname and IP address using C program.

We will be using the following functions :-

gethostname() : The gethostname function retrieves the standard host name for the local computer.



gethostbyname() : The gethostbyname function retrieves host information corresponding to a host name from a host database.

inet_ntoa() : The inet_ntoa function converts an (Ipv4) Internet network address into an ASCII string in Internet standard dotted-decimal format.

C/C++

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// C program to display hostname
// and IP address
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
  
// Returns hostname for the local computer
void checkHostName(int hostname)
{
    if (hostname == -1)
    {
        perror("gethostname");
        exit(1);
    }
}
  
// Returns host information corresponding to host name
void checkHostEntry(struct hostent * hostentry)
{
    if (hostentry == NULL)
    {
        perror("gethostbyname");
        exit(1);
    }
}
  
// Converts space-delimited IPv4 addresses
// to dotted-decimal format
void checkIPbuffer(char *IPbuffer)
{
    if (NULL == IPbuffer)
    {
        perror("inet_ntoa");
        exit(1);
    }
}
  
// Driver code
int main()
{
    char hostbuffer[256];
    char *IPbuffer;
    struct hostent *host_entry;
    int hostname;
  
    // To retrieve hostname
    hostname = gethostname(hostbuffer, sizeof(hostbuffer));
    checkHostName(hostname);
  
    // To retrieve host information
    host_entry = gethostbyname(hostbuffer);
    checkHostEntry(host_entry);
  
    // To convert an Internet network
    // address into ASCII string
    IPbuffer = inet_ntoa(*((struct in_addr*)
                           host_entry->h_addr_list[0]));
  
    printf("Hostname: %s\n", hostbuffer);
    printf("Host IP: %s", IPbuffer);
  
    return 0;
}

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Output:

Hostname: cContainer
Host IP: 10.98.162.101

Output varies machine to machine




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