#include	<stdio.h>
#include	<sys/types.h>
#include	<utmp.h>
#include	<fcntl.h>
#include	<stdlib.h>
#include	<unistd.h>

/*
 *	who version 1	- read /var/run/utmp or argv[1], list its contents
 */

void show_info( struct utmp *utbufp );

int main(int ac, char *av[])
{
	struct utmp	utbuf;		/* read info into here */
	int		utmpfd;		/* read from this descriptor */
	char		*info = ( ac > 1 ? av[1] : UTMP_FILE);

	if ( (utmpfd = open( info, O_RDONLY )) == -1 ){
		fprintf(stderr,"%s: cannot open %s\n", *av, info);
		exit(1);
	}

	while ( read( utmpfd, &utbuf, sizeof(utbuf) ) == sizeof(utbuf) )
		show_info( &utbuf );
	close( utmpfd );
	return 0;			/* went ok			*/
}
/*
 *	show info()
 *		displays contents of utmp struct in human-readable form
 *		note: these sizes should not be hardwired
 *		warn: these strings might not be nul-terminated, see docs
 */
void show_info( struct utmp *utbufp )
{
	if ( utbufp->ut_type != USER_PROCESS )
		return;

	printf("%-8.32s", utbufp->ut_name);		/* the logname	*/
			/* better: "%-8.*s",UT_NAMESIZE,utbufp->ut_name) */
	printf(" ");					/* a space	*/
	printf("%-8.8s", utbufp->ut_line);		/* the tty	*/
		/* 8 chrs, limit to 8 chrs, left justify */
	printf(" ");					/* a space	*/
	printf("%10ld", (long) utbufp->ut_time);	/* login time	*/
	printf(" ");					/* a space	*/
	printf("(%.256s)", utbufp->ut_host);		/* the host	*/
		/* limit to 256 no min */
	printf("\n");					/* newline	*/
}
/*
 * idea: produce output like:
wuensch  pts/1        Feb  4 10:42 (palantir2.unix.fas.harvard.edu)
jol7257  pts/2        Feb  5 20:16 (c-68-35-133-39.hsd1.al.comcast.net)
vyc921   pts/3        Feb  6 20:35 (65.112.8.130)
 */