nested alarm signals (fwd)

Eugene Tsyrklevich eugene at
Thu Jun 15 21:52:06 CDT 2000

> > Even if there was such a rule for a single process, it
> > seems odd to me that the child process for would be
> > affected by the fact that it was run from within an alarm signal
> > handler.
> There are a large number of system calls that are unsafe to make while
> inside a signal handler.  Any attempt to call these may result in
> incorrect, undefined, or otherwise disastrous behavior.  I was looking
> for a complete list, but failed to find one.  However, I'm certain that
> among them are: fork, exec, read, and write.

POSIX.1 requires all of the above functions to be reentrant. Thus you can use them in your signal handlers.
see 'Advanced Programming in the Unix Environment' page 278

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