Add a utmp option if built with utempter, GitHub issue 5657 from Damian Nowak.

options-table.c

@@ -743,6 +743,15 @@ const struct options_table_entry options_table[] = {
 		  "'User0', 'User1' and so on."
 	},
 
+#ifdef HAVE_UTEMPTER
+	{ .name = "utmp",
+	  .type = OPTIONS_TABLE_FLAG,
+	  .scope = OPTIONS_TABLE_SERVER,
+	  .default_num = 1,
+	  .text = "Whether to maintain utmp records."
+	},
+#endif
+
 	{ .name = "variation-selector-always-wide",
 	  .type = OPTIONS_TABLE_FLAG,
 	  .scope = OPTIONS_TABLE_SERVER,

options.c

@@ -1406,6 +1406,14 @@ options_push_changes(const char *name)
 				tty_keys_build(&loop->tty);
 		}
 	}
+	if (strcmp(name, "utmp") == 0) {
+		RB_FOREACH(wp, window_pane_tree, &all_window_panes) {
+			if (options_get_number(global_options, name))
+				window_pane_utmp_add(wp);
+			else
+				window_pane_utmp_remove(wp);
+		}
+	}
 	if (strcmp(name, "status") == 0 ||
 	    strcmp(name, "status-interval") == 0)
 		status_timer_start_all();

server-fn.c

@@ -363,10 +363,7 @@ server_destroy_pane(struct window_pane *wp, int notify)
 	u_int			 sy = screen_size_y(&wp->base);
 
 	if (wp->fd != -1) {
-#ifdef HAVE_UTEMPTER
+		window_pane_utmp_remove(wp);
-		utempter_remove_record(wp->fd);
-		kill(getpid(), SIGCHLD);
-#endif
 		bufferevent_free(wp->event);
 		wp->event = NULL;
 		close(wp->fd);

spawn.c

@@ -322,6 +322,7 @@ spawn_pane(struct spawn_context *sc, char **cause)
 			sc->wp0->event = NULL;
 		}
 		if (sc->wp0->fd != -1) {
+			window_pane_utmp_remove(sc->wp0);
 			close(sc->wp0->fd);
 			sc->wp0->fd = -1;
 		}
@@ -579,16 +580,8 @@ spawn_pane(struct spawn_context *sc, char **cause)
 	_exit(1);
 
 complete:
-#ifdef HAVE_UTEMPTER
-	if (~new_wp->flags & PANE_EMPTY) {
-		xasprintf(&cp, "tmux(%lu).%%%u", (long)getpid(), new_wp->id);
-		utempter_add_record(new_wp->fd, cp);
-		kill(getpid(), SIGCHLD);
-		free(cp);
-	}
-#endif
-
 	new_wp->flags &= ~PANE_EXITED;
+	window_pane_utmp_add(new_wp);
 
 	sigprocmask(SIG_SETMASK, &oldset, NULL);
 	window_pane_set_event(new_wp);

tmux.1

@@ -5262,6 +5262,23 @@ For example:
 set \-s user\-keys[0] "\ee[5;30012\[ti]"
 bind User0 resize\-pane \-L 3
 .Ed
+.It Xo Ic utmp
+.Op Ic on | off
+.Xc
+Maintain utmp records for panes using
+.Xr utempter 3 .
+The default is on.
+Turning this option off asks utempter to remove existing records and prevents
+new records from being added.
+Turning it on asks utempter to add records for existing panes with running
+commands.
+Empty panes are not recorded.
+Updates to wtmp are performed by
+.Xr utempter 3
+according to the system configuration; existing history is not erased.
+This option has no effect if
+.Nm
+was built without utempter support.
 .It Xo Ic variation\-selector\-always\-wide
 .Op Cm on | off
 .Xc

tmux.h

@@ -1355,6 +1355,7 @@ struct window_pane {
 #define PANE_CAPTUREALLKEYS 0x100000
 #define PANE_FLOATOVERZOOM 0x200000
 #define PANE_CLOSEONCANCEL 0x400000
+#define PANE_UTMP 0x800000
 
 	bitstr_t	*sync_dirty;
 	u_int		 sync_dirty_size;
@@ -3725,6 +3726,8 @@ struct window	*window_find_by_id(u_int);
 void		 window_update_activity(struct window *);
 struct window	*window_create(u_int, u_int, u_int, u_int);
 void		 window_pane_set_event(struct window_pane *);
+void		 window_pane_utmp_add(struct window_pane *);
+void		 window_pane_utmp_remove(struct window_pane *);
 void		 window_pane_wait_finish(struct window_pane *);
 struct window_pane *window_get_active_at(struct window *, u_int, u_int);
 struct window_pane *window_find_string(struct window *, const char *);

window.c

@@ -1579,6 +1579,46 @@ window_pane_scrollbar_redraw_visibility(struct window_pane *wp)
 	server_redraw_window(wp->window);
 }
 
+#ifdef HAVE_UTEMPTER
+void
+window_pane_utmp_add(struct window_pane *wp)
+{
+	char	*cp;
+
+	if (wp->fd == -1 ||
+	    (wp->flags & (PANE_EMPTY|PANE_EXITED|PANE_UTMP)) ||
+	    !options_get_number(global_options, "utmp"))
+		return;
+	xasprintf(&cp, "tmux(%lu).%%%u", (long)getpid(), wp->id);
+	utempter_add_record(wp->fd, cp);
+	kill(getpid(), SIGCHLD);
+	wp->flags |= PANE_UTMP;
+	free(cp);
+}
+#else
+void
+window_pane_utmp_add(__unused struct window_pane *wp)
+{
+}
+#endif
+
+#ifdef HAVE_UTEMPTER
+void
+window_pane_utmp_remove(struct window_pane *wp)
+{
+	if (~wp->flags & PANE_UTMP)
+		return;
+	utempter_remove_record(wp->fd);
+	kill(getpid(), SIGCHLD);
+	wp->flags &= ~PANE_UTMP;
+}
+#else
+void
+window_pane_utmp_remove(__unused struct window_pane *wp)
+{
+}
+#endif
+
 static void
 window_pane_destroy(struct window_pane *wp)
 {
@@ -1597,10 +1637,7 @@ window_pane_destroy(struct window_pane *wp)
 		wp->event = NULL;
 	}
 	if (wp->fd != -1) {
-#ifdef HAVE_UTEMPTER
+		window_pane_utmp_remove(wp);
-		utempter_remove_record(wp->fd);
-		kill(getpid(), SIGCHLD);
-#endif
 		close(wp->fd);
 		wp->fd = -1;
 	}