Programming

#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>

extern int errno;

void catcher( int sig ) {
    printf( "Signal catcher called for signal %d\n", sig );
}

void timestamp( char *str ) 
{
    time_t t;
    time( T );
    printf( "The time %s is %s\n", str, ctime(T) );
}

int main( int argc, char *argv[] ) 
{
    struct sigaction sigact;
    sigset_t waitset;
    int sig;
    int result = 0;

    sigemptyset( &sigact.sa_mask );
    sigact.sa_flags = 0;
    sigact.sa_handler = catcher;

    sigaction( SIGUSR1, &sigact, NULL );
    sigaction( SIGUSR2, &sigact, NULL );
    sigaction( SIGALRM, &sigact, NULL );
    sigaction( SIGHUP,  &sigact, NULL );

    sigemptyset( &waitset );
    sigaddset( &waitset, SIGUSR1);
    sigaddset( &waitset, SIGUSR2);
    sigaddset( &waitset, SIGALRM);
    sigaddset( &waitset, SIGHUP);

    

    sigprocmask( SIG_BLOCK, &waitset, NULL );

    while(1)
    {
        timestamp( "before sigwait()" );
        result = sigwait(&saitset, &sig) ;
        if(result == 0)
        {
            printf( "sigwait() returned for signal %d\n", sig );
        else 
        {
            printf( "sigwait() returned error number %d\n", errno );
            perror( "sigwait() function failed\n" );
        }

        timestamp( "after sigwait()" );
    }
    return( result );
}