Wait + signals We had some bugs here which are hard to test in testsuite. Bug 1280 (http://busybox.net/bugs/view.php?id=1280): was misbehaving in interactive ash. Correct behavior: $ sleep 20 & $ wait ^C $ wait ^C $ wait ^C ... Bug 1984 (http://busybox.net/bugs/view.php?id=1984): traps were not triggering: trap_handler_usr () { echo trap usr } trap_handler_int () { echo trap int } trap trap_handler_usr USR1 trap trap_handler_int INT sleep 3600 & echo "Please do: kill -USR1 $$" echo "or: kill -INT $$" while true; do wait; echo wait interrupted; done Bug 189 (https://bugs.busybox.net/show_bug.cgi?id=189) func() { sleep 1 } while (true); do func echo Looping done ^C was observed to make ash processes geometrically multiply (!) instead of exiting. (true) in subshell does not seem to matter, as another user reports the same with: trap "echo USR1" USR1 while true; do echo Sleeping sleep 5 done Compat note. Bash version 3.2.0(1) exits this script at the receipt of SIGINT _only_ if it had two last children die from it. The following trace was obtained while periodically running "killall -SIGINT sleep; sleep 0.1; kill -SIGINT <bash_PID>": 23:48:32.376707 clone(...) = 13528 23:48:32.388706 waitpid(-1, 0xffc832ec, 0) = ? ERESTARTSYS (To be restarted) 23:48:32.459761 --- SIGINT (Interrupt) @ 0 (0) --- kill -SIGINT <bash_PID> is ignored, back to waiting: 23:48:32.463706 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 13528 sleep exited with 0 23:48:37.377557 --- SIGCHLD (Child exited) @ 0 (0) --- 23:48:37.378451 clone(...) = 13538 23:48:37.390708 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 13538 sleep was killed by "killall -SIGINT sleep" 23:48:38.523944 --- SIGCHLD (Child exited) @ 0 (0) --- 23:48:38.524861 clone(...) = 13542 23:48:38.538706 waitpid(-1, 0xffc832ec, 0) = ? ERESTARTSYS (To be restarted) 23:48:38.624761 --- SIGINT (Interrupt) @ 0 (0) --- kill -SIGINT <bash_PID> is ignored, back to waiting: 23:48:38.628706 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 13542 sleep exited with 0 23:48:43.525674 --- SIGCHLD (Child exited) @ 0 (0) --- 23:48:43.526563 clone(...) = 13545 23:48:43.538709 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 13545 sleep was killed by "killall -SIGINT sleep" 23:48:44.466848 --- SIGCHLD (Child exited) @ 0 (0) --- 23:48:44.467735 clone(...) = 13549 23:48:44.481706 waitpid(-1, 0xffc832ec, 0) = ? ERESTARTSYS (To be restarted) 23:48:44.567757 --- SIGINT (Interrupt) @ 0 (0) --- kill -SIGINT <bash_PID> is ignored, back to waiting: 23:48:44.571706 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 13549 sleep exited with 0 23:48:49.468553 --- SIGCHLD (Child exited) @ 0 (0) --- 23:48:49.469445 clone(...) = 13551 23:48:49.481708 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 13551 sleep was killed by "killall -SIGINT sleep" 23:48:50.515837 --- SIGCHLD (Child exited) @ 0 (0) --- 23:48:50.516718 clone(...) = 13555 23:48:50.530706 waitpid(-1, 0xffc832ec, 0) = ? ERESTARTSYS (To be restarted) 23:48:50.615761 --- SIGINT (Interrupt) @ 0 (0) --- kill -SIGINT <bash_PID> is ignored, back to waiting: 23:48:50.619705 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 13555 sleep was killed by "killall -SIGINT sleep". This is the second one in a row. Kill ourself: 23:48:51.504604 kill(13515, SIGINT) = 0 23:48:51.504689 --- SIGINT (Interrupt) @ 0 (0) --- 23:48:51.504915 +++ killed by SIGINT +++ As long as there is at least one "sleep 5" which exited successfully (not killed by SIGINT), bash continues. This is not documented anywhere AFAIKS. Why keyboard ^C acts differently? 00:08:07.655985 clone(...) = 14270 00:08:07.669707 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 14270 00:08:12.656872 --- SIGCHLD (Child exited) @ 0 (0) --- 00:08:12.657743 clone(...) = 14273 00:08:12.671708 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 14273 00:08:13.810778 --- SIGINT (Interrupt) @ 0 (0) --- 00:08:13.818705 kill(14269, SIGINT) = 0 00:08:13.820103 --- SIGINT (Interrupt) @ 0 (0) --- 00:08:13.820925 +++ killed by SIGINT +++ Perhaps because at the moment bash got SIGINT it had no children? (it did not manage to spawn new sleep yet, see the trace)