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Full Discussion: Trying to block signal
Top Forums UNIX for Dummies Questions & Answers Trying to block signal Post 302465034 by joker40 on Thursday 21st of October 2010 02:00:16 PM
Old 10-21-2010
Trying to block signal

I have this code that doesnt do what it is suppose to do. It should block signal that I send while process is running. I press control+z while this process is running and it should be blocked but it isnt. When i press control+z it gives me this....
[1]+ Stopped
When I change SIGTSP into SIGINT then it works as it should. I press control+c and it ignores it and continues executing my program.
Can anyone tell me why this is happening.

Code:
  sigset_t s;
  int j = 0;
  sigemptyset(&s);
  sigaddset(&first,SIGTSTP);

  for (i = 0 ; i < 10 ; i++){
     sleep(5);
     if ( sigprocmask(SIG_BLOCK,&first,NULL)==-1)
        break;

     fprintf("print something here\n");

  }

 

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SIGSETMASK(3)						   BSD Library Functions Manual 					     SIGSETMASK(3)

NAME
sigsetmask -- set current signal mask LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <signal.h> int sigsetmask(int mask); sigmask(signum); DESCRIPTION
This interface is made obsolete by: sigprocmask(2). sigsetmask() sets the current signal mask Signals are blocked from delivery if the corresponding bit in mask is a 1; the macro sigmask() is provided to construct the mask for a given signum. The system quietly disallows SIGKILL or SIGSTOP to be blocked. RETURN VALUES
The previous set of masked signals is returned. EXAMPLES
The following example using sigsetmask(): int omask; omask = sigblock(sigmask(SIGINT) | sigmask(SIGHUP)); ... sigsetmask(omask & ~(sigmask(SIGINT) | sigmask(SIGHUP))); Could be converted literally to: sigset_t set, oset; sigemptyset(&set); sigaddset(&set, SIGINT); sigaddset(&set, SIGHUP); sigprocmask(SIG_BLOCK, &set, &oset); ... sigdelset(&oset, SIGINT); sigdelset(&oset, SIGHUP); sigprocmask(SIG_SETMASK, &oset, NULL); Another, clearer, alternative is: sigset_t set; sigemptyset(&set); sigaddset(&set, SIGINT); sigaddset(&set, SIGHUP); sigprocmask(SIG_BLOCK, &set, NULL); ... sigprocmask(SIG_UNBLOCK, &set, NULL); To completely clear the signal mask using sigsetmask() one can do: (void) sigsetmask(0); Which can be expressed via sigprocmask(2) as: sigset_t eset; sigemptyset(&eset); (void) sigprocmask(SIG_SETMASK, &eset, NULL); SEE ALSO
kill(2), sigaction(2), sigprocmask(2), sigsuspend(2), sigblock(3), sigsetops(3), sigvec(3) HISTORY
The sigsetmask() function call appeared in 4.2BSD and has been deprecated. BSD
August 10, 2002 BSD
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