linux 信号

#include <stdlib.h> 
#include <stdio.h> 
#include <errno.h> 
#include <string.h> 
#include <iostream>
#include <unistd.h>
#include <signal.h>

using namespace std;

typedef void (*sighandler_t)(int);
void handler( int sig )
{
    cout << "sig = " << sig << endl;
}

int main(int argc, char *argv[]) 
{ 
    sighandler_t oldHandler = signal(SIGINT, handler);

    if ( oldHandler == SIG_ERR ) exit(1);
    
    sleep(1);

    if ( signal(SIGINT, oldHandler) == SIG_ERR ) exit(1);

    sleep(10);  
    return 0;
}