sigpause

Purpose

     Atomically  releases blocked  signals  and  waits for  an
     interrupt.

Syntax

     int sigpause (sigmask)
     int sigmask;

Description

     The sigpause  system call sets the  process's signal mask
     to the value of the  sigmask parameter and then and waits
     for a signal to arrive.  Upon return, the previous signal
     mask is restored.  The sigpause system call terminates by
     being  interrupted, returning  -1, and  setting errno  to
     EINTR.

     The sigpause system  call sets the signal  mask and waits
     for  an interrupt  as one  atomic operation.   This means
     that  signals  cannot  occur between  the  operations  of
     setting the mask and waiting  for a signal.  If a program
     invokes the sigsetmask and pause system calls separately,
     then  a signal  that  occurs between  these system  calls
     might not be noticed by pause.

     In  normal  usage,  a  signal is  blocked  by  using  the
     sigblock  system  call at  the  beginning  of a  critical
     section.  The  process then  determines whether  there is
     work for it  to do.  If no  work is to be  done, then the
     process waits for work by  calling sigpause with the mask
     previously returned by sigblock.

Return Value

     If  the  signal is  caught  by  the calling  process  and
     control  is returned  from the  signal handler,  then the
     calling  process  resumes  execution after  the  sigpause
     system call, which always returns  a value of -1 and sets
     errno to EINTR.

Related Information

     In   this    book:    "pause,"    "sigblock,"   "signal,"
     "sigsetmask," and "sigvec."