signal

 

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 Standard C Library Functions                           signal(3C)
 
 
 


NAME
      signal, sigset, sighold,  sigrelse,  sigignore,  sigpause  -
      simplified signal management for application processes
 


SYNOPSIS
      #include <signal.h>
 
      void (*signal (int sig, void (*disp)(int)))(int);
 
      void (*sigset(int sig, void (*disp)(int)))(int);
 
      int sighold(int sig);
 
      int sigrelse(int sig);
 
      int sigignore(int sig);
 
      int sigpause(int sig);
 


DESCRIPTION
      These functions provide  simplified  signal  management  for
      application  processes. See signal(3HEAD) for an explanation
      of general signal concepts.
 
      The signal() and sigset() functions modify  signal  disposi-
      tions.  The  _s_i_g argument specifies the signal, which may be
      any signal except SIGKILL and  SIGSTOP.  The  _d_i_s_p  argument
      specifies  the  signal's  disposition, which may be SIG_DFL,
      SIG_IGN, or the address of a signal handler. If signal()  is
      used,  _d_i_s_p  is  the address of a signal handler, and _s_i_g is
      not  SIGILL, SIGTRAP, or  SIGPWR, the system first sets  the
      signal's disposition to  SIG_DFL before executing the signal
      handler. If sigset() is used and _d_i_s_p is the  address  of  a
      signal handler, the system adds _s_i_g to the calling process's
      signal  mask before executing the signal handler;  when  the
      signal  handler  returns,  the  system  restores the calling
      process's signal mask to its state prior to the delivery  of
      the  signal.  In  addition,  if sigset() is used and _d_i_s_p is
      equal to  SIG_HOLD, _s_i_g is added to  the  calling  process's
      signal mask and the signal's disposition remains unchanged.
 
      The sighold() function adds _s_i_g  to  the  calling  process's
      signal mask.
 
      The  sigrelse()  function  removes  _s_i_g  from  the   calling
      process's signal mask.
 
      The sigignore() function sets  the  disposition  of  _s_i_g  to
      SIG_IGN.
 
      The  sigpause()  function  removes  _s_i_g  from  the   calling
      process's  signal  mask   and  suspends  the calling process
 
 
 
 SunOS 5.8           Last change: 27 Jun 1996                    1
 
 
 
 
 
 
 Standard C Library Functions                           signal(3C)
 
 
 
      until a signal is received.
 
 RETURN VALUES
      Upon successful completion, signal()  returns  the  signal's
      previous  disposition.  Otherwise,  it  returns  SIG_ERR and
      sets errno to indicate the error.
 
      Upon successful completion, sigset() returns SIG_HOLD if the
      signal had been blocked or the signal's previous disposition
      if it had not been blocked. Otherwise, it  returns   SIG_ERR
      and sets errno to indicate the error.
 
      Upon successful completion,  sighold(),  sigrelse(),  sigig-
      nore(),  and  sigpause(),  return  0. Otherwise, they return
      -1 and set  errno to indicate the error.
 
 ERRORS
      These functions fail if:
 
      EINTR A signal was caught during the execution sigpause().
 
      EINVAL
            The value of the _s_i_g argument is not a valid signal or
            is equal to  SIGKILL or  SIGSTOP.
 
 USAGE
      The sighold() function used in conjunction  with  sigrelse()
      or  sigpause()  may be used to establish critical regions of
      code that require the delivery of a signal to be temporarily
      deferred.
 
      If signal() or sigset() is used to set   SIGCHLD's  disposi-
      tion  to a signal handler, SIGCHLD will not be sent when the
      calling process's children are stopped or continued.
 
      If any of the above functions  are  used  to  set  SIGCHLD's
      disposition   to   SIG_IGN,   the  calling  process's  child
      processes will not create zombie processes  when  they  ter-
      minate  (see  exit(2)).  If the calling process subsequently
      waits for its children, it blocks until all of its  children
      terminate;  it then returns -1 with errno set to ECHILD (see
      wait(2) and waitid(2)).
 
      The system guarantees that if more than one instance of  the
      same  signal  is generated to a process, at least one signal
      will be received.  It does not guarantee  the  reception  of
      every generated signal.
 


SEE ALSO
      exit(2),  kill(2),   pause(2),   sigaction(2),   sigsend(2),
      wait(2), waitid(2), signal(3HEAD)
 
 
 
 
 SunOS 5.8           Last change: 27 Jun 1996                    2
 
 
 

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