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Blocking a signal means telling the operating system to hold it and
deliver it later. Generally, a program does not block signals
indefinitely—it might as well ignore them by setting their actions to
SIG_IGN. But it is useful to block signals briefly, to prevent
them from interrupting sensitive operations. For instance:
sigprocmask function to block signals while you
modify global variables that are also modified by the handlers for these
signals.
sa_mask in your sigaction call to block
certain signals while a particular signal handler runs. This way, the
signal handler can run without being interrupted itself by signals.
| • Why Block: | The purpose of blocking signals. | |
| • Signal Sets: | How to specify which signals to block. | |
| • Process Signal Mask: | Blocking delivery of signals to your process during normal execution. | |
| • Testing for Delivery: | Blocking to Test for Delivery of a Signal. | |
| • Blocking for Handler: | Blocking additional signals while a handler is being run. | |
| • Checking for Pending Signals: | Checking for Pending Signals | |
| • Remembering a Signal: | How you can get almost the same effect as blocking a signal, by handling it and setting a flag to be tested later. |