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Atari Mega Archive 2
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up1510b.tgz
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users.c
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C/C++ Source or Header
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1990-07-23
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2KB
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112 lines
/* users - list the users Author: Terrence W. Holm */
/* Usage: users
*
* A simple users(1) command for MINIX. Assumes tty0
* to tty9 are the only possible login devices.
* See last.c for more robust code for reading wtmp.
*/
#include <sys/types.h>
#include <utmp.h>
#include <stdio.h>
#ifndef WTMP
#define WTMP "/usr/adm/wtmp"
#endif
#define min( a, b ) ( (a < b) ? a : b )
#define BUFFER_SIZE 1024 /* Room for wtmp records */
#define MAX_WTMP_COUNT ( BUFFER_SIZE / sizeof(struct utmp) )
struct utmp wtmp_buffer[MAX_WTMP_COUNT];
main()
{
FILE *f;
long size; /* Number of wtmp records in the file */
int wtmp_count; /* How many to read into wtmp_buffer */
int used = 0;
int user_count = 0;
char users[10][8];
if ((f = fopen(WTMP, "r")) == NULL) /* No login/logout records kept */
exit(0);
if (fseek(f, 0L, 2) != 0 || (size = ftell(f)) % sizeof(struct utmp) != 0) {
fprintf(stderr, "users: invalid wtmp file\n");
exit(1);
}
size /= sizeof(struct utmp); /* Number of records in wtmp */
while (size > 0) {
wtmp_count = (int) min(size, MAX_WTMP_COUNT);
size -= (long) wtmp_count;
fseek(f, size * sizeof(struct utmp), 0);
if (fread(&wtmp_buffer[0], sizeof(struct utmp), wtmp_count, f) !=
wtmp_count) {
fprintf(stderr, "users: read error on wtmp file\n");
exit(1);
}
while (--wtmp_count >= 0) {
int tty;
if (strcmp(wtmp_buffer[wtmp_count].ut_line, "~") == 0) {
Print_Users(user_count, users);
exit(0);
}
tty = wtmp_buffer[wtmp_count].ut_line[3] - '0';
if (tty < 0 || tty > 9) {
fprintf(stderr, "users: encountered unknown tty in wtmp file\n");
exit(1);
}
if (!(used & (1 << tty))) {
used |= 1 << tty;
memcpy(users[user_count], wtmp_buffer[wtmp_count].ut_name, 8);
if (users[user_count][0] != '\0') ++user_count;
}
}
} /* end while( size > 0 ) */
Print_Users(user_count, users);
exit(0);
}
Strncmp(str1, str2)
char *str1;
char *str2;
{
return(strncmp(str1, str2, 8));
}
Print_Users(user_count, users)
int user_count;
char *users;
{
int i;
qsort(users, user_count, 8, Strncmp);
for (i = 0; i < user_count - 1; ++i) {
printf("%.8s ", users);
users += 8;
}
if (user_count > 0) printf("%.8s\n", users);
}