who命令

who1.c

#include <stdio.h>
#include <utmp.h>
#include <fcntl.h>
#include <unistd.h>

#define SHOWHOST /*include remote machine on output*/

show_info(struct utmp *utbufp)
{
printf("% -8.8s", utbufp->ut_name);//the logname
printf(" ");//a space
printf("% -8.8s", utbufp->ut_line);//the tty
printf(" ");//a space
printf("% -10ld", utbufp->ut_time);//login time
printf(" ");//a space
#ifdef SHOWHOST
printf("(%s)", utbufp->ut_host);//the host
#endif
printf(" ");//newline
}
int main()
{
struct utmp current_record; /*read info into here*/
int utmpfd; /*read from this descriptor*/
int reclen = sizeof(current_record);

if ((utmpfd = open(UTMP_FILE, O_RDONLY)) == -1)
{
perror(UTMP_FILE);/*UTMP_FILE is utmp.h*/
exit(1);
}

while(read(utmpfd, &current_record, reclen) == reclen)
show_info(&current_record);
close(utmpfd);
return 0;/*went ok*/

}

who2.c

#include <stdio.h>
#include <utmp.h>
#include <fcntl.h>
#include <unistd.h>
//who2 added
#include <time.h>

#define SHOWHOST /*include remote machine on output*/

void show_info(struct utmp *utbufp);
//who2 added
void showtime(long);

int main()
{
struct utmp current_record; /*read info into here*/
int utmpfd; /*read from this descriptor*/
int reclen = sizeof(current_record);

if ((utmpfd = open(UTMP_FILE, O_RDONLY)) == -1)
{
perror(UTMP_FILE);/*UTMP_FILE is utmp.h*/
exit(1);
}

while(read(utmpfd, &current_record, reclen) == reclen)
show_info(&current_record);
close(utmpfd);
return 0;/*went ok*/

}

show_info(struct utmp *utbufp)
{
//who2 added
if (utbufp->ut_type != USER_PROCESS)
{
return;
}
//who2 end
printf("% -8.8s", utbufp->ut_name);//the logname
printf(" ");//a space
printf("% -8.8s", utbufp->ut_line);//the tty
printf(" ");//a space
//printf("% -10ld", utbufp->ut_time);//login time
//printf(" ");//a space
showtime(utbufp->ut_time);
#ifdef SHOWHOST
printf("(%s)", utbufp->ut_host);//the host
#endif
printf(" ");//newline
}

//who2 added
void showtime(long timeval)
{
char *cp;//to hold address of time
cp = ctime(&timeval);
printf("%12.12s", cp+4);//pick 12 chars from pos 4
}
//who2 end