Лабораторные

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
 
int out_file;
char *string_to_write = "Hello world! ";
char *new_line = "\n";
 
void wait_for_signal(int signal)
{
    sigset_t signal_to_wait;
    sigemptyset(&signal_to_wait);
    sigaddset(&signal_to_wait, signal);
    sigwaitinfo(&signal_to_wait, NULL);
}
 
void usr2_handler(int signal)
{
    fsync(out_file);
    _exit(0);
}
 
void write_data_to_file()
{
    int line_num;
    while(1)
    {
        for(line_num = 0;line_num < 10; ++line_num)
            write(out_file, string_to_write, strlen(string_to_write));
        write(out_file, new_line, strlen(new_line));
    }
}
 
void read_from_file()
{
    int read_count;
    char buffer[1024];
 
    lseek(out_file, SEEK_SET, 0);
    do
    {
        read_count = read(out_file, buffer, 1024);
        write(STDOUT_FILENO, buffer, read_count);
    }while(read_count == 1024);
    close(out_file);
}
 
void set_sigusr2_handler()
{
    struct sigaction sa;
    memset (&sa, 0, sizeof(sa));
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sa.sa_handler = usr2_handler;
    sigaction(SIGUSR2, &sa, NULL);
}
 
void set_process_signal_mask()
{
    sigset_t signals_to_block;
 
    sigemptyset(&signals_to_block);
    sigaddset(&signals_to_block, SIGUSR1);
    sigaddset(&signals_to_block, SIGCHLD);
    sigprocmask(SIG_SETMASK, &signals_to_block, NULL);
}
 
int main(int argc, char **argv)
{
    pid_t child_pid;
 
    set_process_signal_mask();
    set_sigusr2_handler();
 
    out_file = open(argv[1], O_CREAT | O_TRUNC | O_RDWR, S_IRUSR | S_IWUSR);
    if(out_file == -1) return -1;
 
    child_pid = fork();
    if(child_pid == 0)
    {
        // child
        wait_for_signal(SIGUSR1);
        write_data_to_file();
    }
    else
    {
        // Parent process
        kill(child_pid, SIGUSR1);
        sleep(1);
        kill(child_pid, SIGUSR2);
        wait_for_signal(SIGCHLD);
        read_from_file();
    }
    return EXIT_SUCCESS;
}