gethostbyname example c

/* lookup.c: * Example of gethostbyname(3): * gethostbyname example * gethostbyname example code * supply the hostname as argument you want to lookup * see the sample output below the code */ #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <errno.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> extern int h_errno; int main(int argc,char **argv) { int x, x2; struct hostent *hp; for ( x=1; x<argc; ++x ) { /* * Look up the hostname: */ hp = gethostbyname(argv[x]); if ( !hp ) { //Report lookup failure fprintf(stderr, "%s: host '%s'\n", hstrerror(h_errno), argv[x]); continue; } /* * Report the findings: */ printf("Host %s : \n" ,argv[x]); printf(" Officially:\t%s\n", hp->h_name); fputs(" Aliases:\t",stdout); for ( x2=0; hp->h_aliases[x2]; ++x2 ) { if ( x2 ) { fputs(", ",stdout); } fputs(hp->h_aliases[x2],stdout); } fputc('\n',stdout); printf(" Type:\t\t%s\n", hp->h_addrtype == AF_INET ? "AF_INET" : "AF_INET6"); if ( hp->h_addrtype == AF_INET ) { for ( x2=0; hp->h_addr_list[x2]; ++x2 ) { printf(" Address:\t%s\n", inet_ntoa( *(struct in_addr *) hp->h_addr_list[x2])); } } putchar('\n'); } return 0; } /* * OUTPUT * [sgupta@rhel55x86 chap9] gcc -c -D_GNU_SOURCE -Wall -Wreturn-type lookup.c gcc lookup.o -o lookup [sgupta@rhel55x86 chap9]$ ./lookup www.lwn.net sunsite.unc.edu ftp.redhat.com Host www.lwn.net : Officially: lwn.net Aliases: www.lwn.net Type: AF_INET Address: 206.168.112.90 Host sunsite.unc.edu : Officially: sunsite.unc.edu Aliases: Type: AF_INET Address: 152.2.254.81 Host ftp.redhat.com : Officially: ftp.redhat.com Aliases: Type: AF_INET Address: 206.132.41.212 Address: 208.178.165.228 [sgupta@rhel55x86 chap9] $ */