Blocking Signals

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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:

• You can use the sigprocmask function to block signals while you modify global variables that are also modified by the handlers for these signals.

• You can set 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.

Menu

• 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.