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signal() and sigaction() ?

Posted on 2002-05-26
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Hi
Can anyone tell me the difference between signal and sigaction? I am having an alarm which interrupts a blocking recvfrom call every 10 seconds. When I used signal to specify the function to handle SIGALRM signal, the signal was handled but the recvfrom did not return after the alarm was processed.
When I used sigaction, recvfrom call was interrupted and after executing the signal handling function it proceded to the next line in my program. I thought both signal and sigaction could be used interchangably for
specifying the signal handling functions.
Thanks
Sreekumar.
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Question by:sreekumarvk
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ecw earned 400 total points
ID: 7036600
BSD semantics - some sys calls are restartable if a signal is received during the call.  sigaction has a flag to enable this - SA_RESTART.  Set this and both your tests will do the same.  If you're were using SYSV semantics, your recvfrom would return an EINTR if you used signal, and an alarm was received.
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by:sreekumarvk
ID: 7037373
Hi ecw,
Thanks for the help.. Now things are more clear.
Sreekumar
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by:ecw
ID: 7037871
No worries.  There a good description of signal handling in the comp.unix.programming faq.  It might apply to Linux too, although not everything is the same, the faq is a good place to start, see
  http://www.erlenstar.demon.co.uk/unix/faq_toc.html
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