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(libc.info)Blocking Signals

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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.

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.