Fixed a bug that caused last(1) to be extremely slow in some cases, and

made other performance improving changes. This improves the performance
of last(1) by as much as 32 times in some cases, and in more typical cases
is about twice as fast.
Added a BUGS section to the manual page to describe the behavior of last(1)
when a login shell terminates abnormally (and thus doesn't write a logout
record to the wtmp file).

2 files changed, 83 insertions, 83 deletions

diff --git a/usr.bin/last/last.1 b/usr.bin/last/last.1
index 27a214d..c746d5b 100644
--- a/usr.bin/last/last.1
+++ b/usr.bin/last/last.1
@@ -117,6 +117,11 @@ login data base
 .Xr lastcomm 1 ,
 .Xr utmp 5 ,
 .Xr ac 8
+.Sh BUGS
+If a login shell should terminate abnormally for some reason, it is likely
+that a logout record won't be written to the wtmp file. In this case,
+.Nm last
+will indicate the logout time as "shutdown".
 .Sh HISTORY
 .Nm Last
 appeared in
diff --git a/usr.bin/last/last.c b/usr.bin/last/last.c
index 1d18600..ba7214f 100644
--- a/usr.bin/last/last.c
+++ b/usr.bin/last/last.c
@@ -54,6 +54,7 @@ static char sccsid[] = "@(#)last.c	8.2 (Berkeley) 4/2/94";
 #include <time.h>
 #include <unistd.h>
 #include <utmp.h>
+#include <sys/queue.h>
 
 #define	NO	0				/* false/no */
 #define	YES	1				/* true/yes */
@@ -70,23 +71,23 @@ typedef struct arg {
 } ARG;
 ARG	*arglist;				/* head of linked list */
 
-typedef struct ttytab {
+LIST_HEAD(ttylisthead, ttytab) ttylist;
+
+struct ttytab {
 	long	logout;				/* log out time */
 	char	tty[UT_LINESIZE + 1];		/* terminal name */
-	struct ttytab	*next;			/* linked list pointer */
-} TTY;
-TTY	*ttylist;				/* head of linked list */
+	LIST_ENTRY(ttytab) list;
+};
 
 static long	currentout,			/* current logout value */
 		maxrec;				/* records to display */
 static char	*file = _PATH_WTMP;		/* wtmp file */
 
 void	 addarg __P((int, char *));
-TTY	*addtty __P((char *));
 void	 hostconv __P((char *));
 void	 onintr __P((int));
 char	*ttyconv __P((char *));
-int	 want __P((struct utmp *, int));
+int	 want __P((struct utmp *));
 void	 wtmp __P((void));
 
 int
@@ -158,12 +159,14 @@ void
 wtmp()
 {
 	struct utmp	*bp;			/* current structure */
-	TTY	*T;				/* tty list entry */
+	struct ttytab	*tt;				/* ttylist entry */
 	struct stat	stb;			/* stat of file for size */
 	long	bl, delta;			/* time difference */
 	int	bytes, wfd;
 	char	*ct, *crmsg;
 
+	LIST_INIT(&ttylist);
+
 	if ((wfd = open(file, O_RDONLY, 0)) < 0 || fstat(wfd, &stb) == -1)
 		err(1, "%s", file);
 	bl = (stb.st_size + sizeof(buf) - 1) / sizeof(buf);
@@ -183,14 +186,16 @@ wtmp()
 			 */
 			if (bp->ut_line[0] == '~' && !bp->ut_line[1]) {
 				/* everybody just logged out */
-				for (T = ttylist; T; T = T->next)
-					T->logout = -bp->ut_time;
+				for (tt = ttylist.lh_first; tt; tt = tt->list.le_next) {
+					LIST_REMOVE(tt, list);
+					free(tt);
+				}
 				currentout = -bp->ut_time;
 				crmsg = strncmp(bp->ut_name, "shutdown",
 				    UT_NAMESIZE) ? "crash" : "shutdown";
-				if (want(bp, NO)) {
+				if (want(bp)) {
 					ct = ctime(&bp->ut_time);
-				printf("%-*.*s  %-*.*s %-*.*s %10.10s %5.5s \n",
+					printf("%-*.*s  %-*.*s %-*.*s %10.10s %5.5s \n",
 					    UT_NAMESIZE, UT_NAMESIZE,
 					    bp->ut_name, UT_LINESIZE,
 					    UT_LINESIZE, bp->ut_line,
@@ -207,58 +212,77 @@ wtmp()
 			 */
 			if ((bp->ut_line[0] == '{' || bp->ut_line[0] == '|')
 			    && !bp->ut_line[1]) {
-				if (want(bp, NO)) {
+				if (want(bp)) {
 					ct = ctime(&bp->ut_time);
-				printf("%-*.*s  %-*.*s %-*.*s %10.10s %5.5s \n",
-				    UT_NAMESIZE, UT_NAMESIZE, bp->ut_name,
-				    UT_LINESIZE, UT_LINESIZE, bp->ut_line,
-				    UT_HOSTSIZE, UT_HOSTSIZE, bp->ut_host,
-				    ct, ct + 11);
+					printf("%-*.*s  %-*.*s %-*.*s %10.10s %5.5s \n",
+					    UT_NAMESIZE, UT_NAMESIZE, bp->ut_name,
+					    UT_LINESIZE, UT_LINESIZE, bp->ut_line,
+					    UT_HOSTSIZE, UT_HOSTSIZE, bp->ut_host,
+					    ct, ct + 11);
 					if (maxrec && !--maxrec)
 						return;
 				}
 				continue;
 			}
-			/* find associated tty */
-			for (T = ttylist;; T = T->next) {
-				if (!T) {
-					/* add new one */
-					T = addtty(bp->ut_line);
-					break;
+			if (bp->ut_name[0] == '\0' || want(bp)) {
+				/* find associated tty */
+				for (tt = ttylist.lh_first; ; tt = tt->list.le_next) {
+					if (tt == NULL) {
+						/* add new one */
+						tt = malloc(sizeof(struct ttytab));
+						if (tt == NULL)
+							err(1, "malloc failure");
+						tt->logout = currentout;
+						strncpy(tt->tty, bp->ut_line, UT_LINESIZE);
+						LIST_INSERT_HEAD(&ttylist, tt, list);
+						break;
+					}
+					if (!strncmp(tt->tty, bp->ut_line, UT_LINESIZE))
+						break;
 				}
-				if (!strncmp(T->tty, bp->ut_line, UT_LINESIZE))
-					break;
-			}
-			if (bp->ut_name[0] && want(bp, YES)) {
-				ct = ctime(&bp->ut_time);
-				printf("%-*.*s  %-*.*s %-*.*s %10.10s %5.5s ",
-				UT_NAMESIZE, UT_NAMESIZE, bp->ut_name,
-				UT_LINESIZE, UT_LINESIZE, bp->ut_line,
-				UT_HOSTSIZE, UT_HOSTSIZE, bp->ut_host,
-				ct, ct + 11);
-				if (!T->logout)
-					puts("  still logged in");
-				else {
-					if (T->logout < 0) {
-						T->logout = -T->logout;
-						printf("- %s", crmsg);
+				if (bp->ut_name[0]) {
+					/*
+					 * when uucp and ftp log in over a network, the entry in
+					 * the utmp file is the name plus their process id.  See
+					 * etc/ftpd.c and usr.bin/uucp/uucpd.c for more information.
+					 */
+					if (!strncmp(bp->ut_line, "ftp", sizeof("ftp") - 1))
+						bp->ut_line[3] = '\0';
+					else if (!strncmp(bp->ut_line, "uucp", sizeof("uucp") - 1))
+						bp->ut_line[4] = '\0';
+					ct = ctime(&bp->ut_time);
+					printf("%-*.*s  %-*.*s %-*.*s %10.10s %5.5s ",
+					    UT_NAMESIZE, UT_NAMESIZE, bp->ut_name,
+					    UT_LINESIZE, UT_LINESIZE, bp->ut_line,
+					    UT_HOSTSIZE, UT_HOSTSIZE, bp->ut_host,
+					    ct, ct + 11);
+					if (!tt->logout)
+						puts("  still logged in");
+					else {
+						if (tt->logout < 0) {
+							tt->logout = -tt->logout;
+							printf("- %s", crmsg);
+						}
+						else
+							printf("- %5.5s",
+							    ctime(&tt->logout)+11);
+						delta = tt->logout - bp->ut_time;
+						if (delta < 86400)
+							printf("  (%5.5s)\n",
+							    asctime(gmtime(&delta))+11);
+						else
+							printf(" (%ld+%5.5s)\n",
+							    delta / 86400,
+							    asctime(gmtime(&delta))+11);
 					}
-					else
-						printf("- %5.5s",
-						    ctime(&T->logout)+11);
-					delta = T->logout - bp->ut_time;
-					if (delta < 86400)
-						printf("  (%5.5s)\n",
-						    asctime(gmtime(&delta))+11);
-					else
-						printf(" (%ld+%5.5s)\n",
-						    delta / 86400,
-						    asctime(gmtime(&delta))+11);
+					LIST_REMOVE(tt, list);
+					free(tt);
+					if (maxrec != -1 && !--maxrec)
+						return;
+				} else {
+					tt->logout = bp->ut_time;
 				}
-				if (maxrec != -1 && !--maxrec)
-					return;
 			}
-			T->logout = bp->ut_time;
 		}
 	}
 	ct = ctime(&buf[0].ut_time);
@@ -270,22 +294,11 @@ wtmp()
  *	see if want this entry
  */
 int
-want(bp, check)
+want(bp)
 	struct utmp *bp;
-	int check;
 {
 	ARG *step;
 
-	if (check)
-		/*
-		 * when uucp and ftp log in over a network, the entry in
-		 * the utmp file is the name plus their process id.  See
-		 * etc/ftpd.c and usr.bin/uucp/uucpd.c for more information.
-		 */
-		if (!strncmp(bp->ut_line, "ftp", sizeof("ftp") - 1))
-			bp->ut_line[3] = '\0';
-		else if (!strncmp(bp->ut_line, "uucp", sizeof("uucp") - 1))
-			bp->ut_line[4] = '\0';
 	if (!arglist)
 		return (YES);
 
@@ -327,24 +340,6 @@ addarg(type, arg)
 }
 
 /*
- * addtty --
- *	add an entry to a linked list of ttys
- */
-TTY *
-addtty(ttyname)
-	char *ttyname;
-{
-	TTY *cur;
-
-	if (!(cur = (TTY *)malloc((u_int)sizeof(TTY))))
-		err(1, "malloc failure");
-	cur->next = ttylist;
-	cur->logout = currentout;
-	memmove(cur->tty, ttyname, UT_LINESIZE);
-	return (ttylist = cur);
-}
-
-/*
  * hostconv --
  *	convert the hostname to search pattern; if the supplied host name
  *	has a domain attached that is the same as the current domain, rip