Reporting IP adress

eclapton1 · 06-27-2004, 07:14 PM

With some assistance, I wrote this code in C to perform the functions of the last command. It displays some of the fields from the wtmp file. Instead of reporting the hostname, I'd like to report the IP address. From the man pages, it looks as though the host command will find IP addresses. But, do I need to use pipes to perform this action? Maybe something like read_fp = popen("host", "r"). Of course, the IP address field may be empty and in this case I can report something such as "empty" and perform no DNS lookup.

Code:

#include <utmp.h>
#include <utmpx.h>
#include <stdio.h>
#include <iostream>

#define WTMP_FILENAME "/var/log/wtmp"

int main()
{

        struct utmp record;
        FILE *fd = fopen(WTMP_FILENAME, "r");

        if (fd == NULL) {
                perror(WTMP_FILENAME);
                return 1;
        }
        while (fread(&record, sizeof record, 1, fd) != 0) {
                printf("%s: %s\t: %s\t", record.ut_line, record.ut_user, record.ut_id);
        }
        return 0;
}

crabboy · 06-27-2004, 11:34 PM

How about using the IP address in the utmp struct.

Code:

             struct utmp {
                short ut_type;              /* type of login */
                pid_t ut_pid;               /* pid of login process */
                char ut_line[UT_LINESIZE];  /* device name of tty - "/dev/" */
                char ut_id[4];              /* init id or abbrev. ttyname */
                char ut_user[UT_NAMESIZE];  /* user name */
                char ut_host[UT_HOSTSIZE];  /* hostname for remote login */
                struct exit_status ut_exit; /* The exit status of a process
                                               marked as DEAD_PROCESS. */
                long ut_session;            /* session ID, used for windowing*/
                struct timeval ut_tv;       /* time entry was made.  */
                int32_t ut_addr_v6[4];      /* IP address of remote host.  */
                char pad[20];               /* Reserved for future use.  */
              };