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C Program to display hostname and IP address
In this section we will see how to see the Host name and IP address of the local system in an easier way. We will write a C program to find the host name and IP.
Some of the following functions are used. These functions have different task. Let us see the functions and their tasks.
| Function | Description |
|---|---|
| gethostname() | It finds the standard host name for the local computer. |
| gethostbyname() | It finds the host information corresponding to a host name from host database |
| iten_ntoa() | It converts an IPv4 Internet network address into an ASCII string into dotted decimal format. |
Example Code
#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>
void check_host_name(int hostname) { //This function returns host name for
local computer
if (hostname == -1) {
perror("gethostname");
exit(1);
}
}
void check_host_entry(struct hostent * hostentry) { //find host info from
host name
if (hostentry == NULL) {
perror("gethostbyname");
exit(1);
}
}
void IP_formatter(char *IPbuffer) { //convert IP string to dotted decimal
format
if (NULL == IPbuffer) {
perror("inet_ntoa");
exit(1);
}
}
main() {
char host[256];
char *IP;
struct hostent *host_entry;
int hostname;
hostname = gethostname(host, sizeof(host)); //find the host name
check_host_name(hostname);
host_entry = gethostbyname(host); //find host information
check_host_entry(host_entry);
IP = inet_ntoa(*((struct in_addr*) host_entry->h_addr_list[0]));
//Convert into IP string
printf("Current Host Name: %s
", host);
printf("Host IP: %s
", IP);
}Output (Tested on Linux System)
Current Host Name: soumyadeep-VirtualBox Host IP: 127.0.1.1
Updated on: 30-Jul-2019
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