Using signal handler in linux

Question

void f(int);
void main()
{
    signal(SIGINT, f);
    int i = 4;
    while(i < 1000)
    {
       sleep(10);
        i++;
     }
}

void f( int signum ){
    printf ( "OUCH \n") ;
}

if I hit "ctr C" while the program is looping, it prints out "OUCH" to the terminal. Is there anyway I can print out the current number that the program is looping using signal handler.

Read [signal(7)](http://man7.org/linux/man-pages/man7/signal.7.html). You are not allowed to call `printf` inside your signal handler - even if most of the time it seems to work. — Basile Starynkevitch, Nov 14 '14 at 06:23

score 1 · Answer 1 · edited May 23 '17 at 12:30

1

You can use global variables to store the value of the loop variable. You can then access this variable from the signal handler. Although you need to be very careful while doing this.

Please go through: Providing/passing argument to signal handler

edited May 23 '17 at 12:30

Community

1
1

answered Nov 14 '14 at 05:39

vvvv

135
10

score 0 · Accepted Answer · answered Nov 14 '14 at 05:37

Yes you can just add a static variable and keep the value in it in each iteration.

void f(int);
static int temp=0;
void main()
{

    int i = 4;
    while(i < 1000)
    {
       sleep(10);
        i++;
        temp=i;
     }
}

void f( int signum ){
    printf ( "OUCH %d \n", temp) ;


}

Using signal handler in linux

2 Answers2