1c.c

/*
============================================================================
Name : 1c
Author : Piyush Singh
Description :  Write a separate program (for each time domain) to set a interval timer in 10sec and
10micro second
a. ITIMER_REAL
b. ITIMER_VIRTUAL
c. ITIMER_PROF
Date: 18th Sep, 2025.
============================================================================
*/


#include <stdio.h>      // For printf(), perror()
#include <stdlib.h>     // For exit()
#include <sys/time.h>   // For setitimer(), struct itimerval
#include <unistd.h>     // For getppid()
#include <signal.h>     // For signal(), SIGPROF

// Signal handler for SIGPROF
void prof_handler(int signum) 
{ 
    printf("📊 ITIMER_PROF triggered: SIGPROF received\n"); 
    exit(0); // Exit program after signal
}

int main() 
{
    // Register signal handler for SIGPROF
    signal(SIGPROF, prof_handler);

    // Define timer structure
    struct itimerval timer;

    // Set initial expiration to 10 seconds and 10 microseconds
    timer.it_value.tv_sec = 10;
    timer.it_value.tv_usec = 10;

    // Set interval to 0 (one-shot timer)
    timer.it_interval.tv_sec = 0;
    timer.it_interval.tv_usec = 0;

    // Start the profiling timer
    if (setitimer(ITIMER_PROF, &timer, NULL) == -1) 
    {
        perror("❌ setitimer failed");
        exit(1);
    }

    printf("🟢 ITIMER_PROF set for 10s + 10μs\n");

    // Consume user + system time to trigger the timer
    for (long i = 0; i < 1e9; i++) getppid();  // Syscall + CPU

    return 0;
}

/*
============================================================================
Output :
gcc -O0 -o 1c 1c.c                                                         ─╯
./1c
🟢 ITIMER_PROF set for 10s + 10μs
📊 ITIMER_PROF triggered: SIGPROF received
============================================================================
*/