add directory study

study/linux-travel/MINIX-1.5/1.5/Source/commands/users.c

@@ -0,0 +1,111 @@
+/*  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);
+}