/* 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); }