Add -B to new-pane to block and return a return code from the process.

cmd-split-window.c

@@ -38,8 +38,8 @@ const struct cmd_entry cmd_new_pane_entry = {
 	.name = "new-pane",
 	.alias = "newp",
 
-	.args = { "bc:de:EfF:hIkl:Lm:p:PR:s:S:t:vx:X:y:Y:Z", 0, -1, NULL },
-	.usage = "[-bdefhIklPvZ] [-c start-directory] [-e environment] "
+	.args = { "bBc:de:EfF:hIkl:Lm:p:PR:s:S:t:vx:X:y:Y:Z", 0, -1, NULL },
+	.usage = "[-bBdefhIklPvZ] [-c start-directory] [-e environment] "
 		 "[-F format] [-l size] [-m message] [-p percentage] "
 		 "[-s style] [-S active-border-style] "
 		 "[-R inactive-border-style] [-x width] [-y height] "
@@ -238,5 +238,15 @@ cmd_split_window_exec(struct cmd *self, struct cmdq_item *item)
 	environ_free(sc.environ);
 	if (input)
 		return (CMD_RETURN_WAIT);
+
+	/*
+	 * With -B, block this command queue item until the pane's command
+	 * exits; window_pane_block_finish() then sets the client return code
+	 * and continues the queue (see server_child_exited()).
+	 */
+	if (args_has(args, 'B')) {
+		new_wp->block_item = item;
+		return (CMD_RETURN_WAIT);
+	}
 	return (CMD_RETURN_NORMAL);
 }

server.c

@@ -497,6 +497,8 @@ server_child_exited(pid_t pid, int status)
 				log_debug("%%%u exited", wp->id);
 				wp->flags |= PANE_EXITED;
 
+				window_pane_block_finish(wp);
+
 				if (window_pane_destroy_ready(wp))
 					server_destroy_pane(wp, 1);
 				break;

tmux.1

@@ -3330,7 +3330,7 @@ but a different format may be specified with
 .Fl F .
 .Tg newp
 .It Xo Ic new\-pane
-.Op Fl bdefhIkPvZ
+.Op Fl bBdefhIkPvZ
 .Op Fl c Ar start\-directory
 .Op Fl e Ar environment
 .Op Fl F Ar format
@@ -3403,6 +3403,22 @@ but also sets the
 option for this pane to
 .Ar message .
 .Pp
+.Fl B
+blocks until the
+.Ar shell\-command
+running in the new pane exits, then returns its exit status as the exit
+code of the issuing client.
+This makes it possible to run a command in a pane from a script and act on
+its result, for example a
+.Xr whiptail 1
+dialog.
+Only the command queue of the issuing client waits; the server and other
+clients are unaffected and the new pane remains interactive.
+If the pane is killed or terminated by a signal, the status is
+.Li 128
+plus the signal number, as for
+.Ic run\-shell .
+.Pp
 .Fl E ,
 or an empty
 .Ar shell\-command ,

tmux.h

@@ -1294,6 +1294,7 @@ struct window_pane {
 	char		 tty[TTY_NAME_MAX];
 	int		 status;
 	struct timeval	 dead_time;
+	struct cmdq_item *block_item;	/* new-pane -B: waiting for pane exit */
 
 	int		 fd;
 	struct bufferevent *event;
@@ -3422,6 +3423,7 @@ 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_block_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 *);
 int		 window_has_floating_panes(struct window *);

window.c

@@ -18,6 +18,7 @@
 
 #include <sys/types.h>
 #include <sys/ioctl.h>
+#include <sys/wait.h>
 
 #include <ctype.h>
 #include <errno.h>
@@ -380,6 +381,15 @@ window_pane_destroy_ready(struct window_pane *wp)
 
 	if (~wp->flags & PANE_EXITED)
 		return (0);
+
+	/*
+	 * If a command queue item is blocked on this pane (new-pane -B), wait
+	 * for the child's exit status to be reaped before destroying it, so
+	 * the correct return code is reported. The PTY EOF and SIGCHLD paths
+	 * otherwise race and the pane could be freed with no status.
+	 */
+	if (wp->block_item != NULL && (~wp->flags & PANE_STATUSREADY))
+		return (0);
 	return (1);
 }
 
@@ -1064,12 +1074,43 @@ window_pane_create(struct window *w, u_int sx, u_int sy, u_int hlimit)
 	return (wp);
 }
 
+/*
+ * Finish a new-pane -B wait: if this pane has a blocked command queue item,
+ * set the issuing client's return code from the pane's exit status and continue
+ * the queue. Idempotent and safe to call from any pane teardown path.
+ */
+void
+window_pane_block_finish(struct window_pane *wp)
+{
+	struct cmdq_item	*item = wp->block_item;
+	struct client		*c;
+	int			 retcode = 0;
+
+	if (item == NULL)
+		return;
+	wp->block_item = NULL;
+
+	if (wp->flags & PANE_STATUSREADY) {
+		if (WIFEXITED(wp->status))
+			retcode = WEXITSTATUS(wp->status);
+		else if (WIFSIGNALED(wp->status))
+			retcode = WTERMSIG(wp->status) + 128;
+	}
+
+	c = cmdq_get_client(item);
+	if (c != NULL && c->session == NULL)
+		c->retval = retcode;
+	cmdq_continue(item);
+}
+
 static void
 window_pane_destroy(struct window_pane *wp)
 {
 	struct window_pane_resize	*r;
 	struct window_pane_resize	*r1;
 
+	window_pane_block_finish(wp);
+
 	window_pane_reset_mode_all(wp);
 	free(wp->searchstr);