#include <signal.h> #include <stdio.h> #include <sys/types.h> #include <unistd.h>

/* When a SIGUSR1 signal arrives, set this variable. */ volatile sig_atomic_t usr_interrupt = 0;

void synch_signal (int sig) { usr_interrupt = 1; }

/* The child process executes this function. */ void child_function (void) { /* Perform initialization. */ printf ("I’m here!!! My pid is %d.\n", (int) getpid ());

/* Let parent know you’re done. */ kill (getppid (), SIGUSR1);

/* Continue with execution. */ puts ("Bye, now...."); exit (0); }

int main (void) { struct sigaction usr_action; sigset_t block_mask; pid_t child_id;

/* Establish the signal handler. */ sigfillset (&block_mask); usr_action.sa_handler = synch_signal; usr_action.sa_mask = block_mask; usr_action.sa_flags = 0; sigaction (SIGUSR1, &usr_action, NULL);

/* Create the child process. */ child_id = fork (); if (child_id == 0) child_function (); /* Does not return. */

/* Busy wait for the child to send a signal. */ while (!usr_interrupt) ;

/* Now continue execution. */ puts ("That’s all, folks!");

return 0; }

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