Next: Pause Problems, Up: Waiting for a Signal

#### 24.8.1 Using `pause`

The simple way to wait until a signal arrives is to call `pause`. Please read about its disadvantages, in the following section, before you use it.

— Function: int pause (void)

> The `pause` function suspends program execution until a signal arrives whose action is either to execute a handler function, or to terminate the process.

> If the signal causes a handler function to be executed, then `pause` returns. This is considered an unsuccessful return (since “successful” behavior would be to suspend the program forever), so the return value is `-1`. Even if you specify that other primitives should resume when a system handler returns (see Interrupted Primitives), this has no effect on `pause`; it always fails when a signal is handled.

> The following `errno` error conditions are defined for this function:

> `EINTR`
>   The function was interrupted by delivery of a signal.

> If the signal causes program termination, `pause` doesn't return (obviously).

> This function is a cancellation point in multithreaded programs. This is a problem if the thread allocates some resources (like memory, file descriptors, semaphores or whatever) at the time `pause` is called. If the thread gets cancelled these resources stay allocated until the program ends. To avoid this calls to `pause` should be protected using cancellation handlers.

> The `pause` function is declared in `unistd.h`.