printiphex.c

/**
 * @brief convert IP from network format to string, if
 *        the only parameter starts with 0x, e.g.
 *        ./printiphex 0x0100007F
 *        => 127.0.0.1
 *        or print the address on network notation otherwise e.g.
 *        ./printiphex 127.0.0.1
 *        => 0x0100007F
 *
 * @param 1th, The ip address to convert from network to
 *             string or reverse.
 *
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define pexit(s) ({perror(s); exit(EXIT_FAILURE);})

int main(int argc, char **argv)
{
        if (argc < 2) {
                printf("Usage: %s IP\n", argv[0]);
                exit(EXIT_FAILURE);
        }

        if (!strncmp("0x", argv[1], 2)) {
                struct in_addr addr = {
                        .s_addr = strtol(argv[1], NULL, 16),
                };

                printf("%s\n", inet_ntoa(addr));
        } else {
                printf("0x%08X\n",  inet_addr(argv[1]));
        }

        return 0;
}