How to use the delay of the signal using sigwait() - c++

Question

on assignment I need to write a program which opens a channel pipe and gives rise to two descendant process and then the parent fills the channel from the input file and then sends the signal SIGQUIT to the descendants, who can read character from channel and send each other signals after reading the next symbol of SIGUSR1 and SIGUSR2 to another descendant was able to start reading, but there was a problem: in a loop reading the parent is stupor, and if debajo the steps then everything is fine and it exits the loop, or if the clean lines of the exec, then exit from the loop occurs. I don't understand what the problem might be. In descendants, I use sigwait to wait. I will present the codes of the parent and descendants below. Please tell me what's wrong? The code of the parent:
#include <iostream>
#include <fstream>
#include <unistd.h>
#include <cstring>
#include <sys/wait.h>
#include <signal.h>
#include <wait.h>
using namespace std;
int main() {
sigset_t new_mask;
sigemptyset(&new_mask);
sigaddset(&new_mask, SIGUSR1);
sigaddset(&new_mask, SIGUSR2);
sigaddset(&new_mask, SIGQUIT);
sigprocmask(SIG_SETMASK, &new_mask, NULL);
int fildes[2];
pipe(fildes);
pid_t pid1;
pid_t pid2;
pid1 = fork();
if (pid1 == 0) {
//execl("1","1", "output1.txt", &fildes[0], &fildes[1],NULL);
close(fildes[0]);
_exit(0);
}
else {
pid2 = fork();
if (pid2 == 0) {
execl("2","2", "output2.txt", &fildes[0], &fildes[1], NULL);
close(fildes[0]);
_exit(0);
}
else {
close(fildes[0]);
cout<<"Parent"<<endl;
ifstream file("input.txt");
if (file.is_open()) {
string str;
bool t = true;
t = (bool)getline(file, str);
while(t){
write(fildes[1], &str[0], strlen(str.c_str()));
cout<<"PARENT пишет:" << str << endl;
cout<< "sdsdsds";
t = (bool)getline(file, str);
}
cout << "aaaaaaaaaaaaaaaaaaaaaaaaa";
killpg(0, SIGQUIT);
file.close();
}
int st1, st2;
waitpid(pid1, &st1, 0);
waitpid(pid2, &st2, 0);
close(fildes[1]);
exit(EXIT_SUCCESS);
}
}
return 0;
}
First child's code:
#include <iostream>
#include <fstream>
#include <unistd.h>
#include <cstring>
#include <sys/wait.h>
#include <signal.h>
#include <wait.h>
#include <cerrno>
using namespace std;
int main(int argc, char** argv) {
int fildes[2];
fildes[0]=*argv[2];
fildes[1]=*argv[3];
close(fildes[1]);
sigset_t mask_sig;
sigemptyset(&mask_sig);
sigaddset(&mask_sig, SIGUSR1);
sigaddset(&mask_sig, SIGQUIT);
ofstream file;
int last_sig;
char ch;
file.open(argv[1], ios::app);
//file << read(fildes[0], &ch, 1) << endl;
sigwait(&mask_sig, &last_sig);
while(read(fildes[0], &ch, 1) > 0){
//file << "a" << endl;
file << ch;
killpg(0, SIGUSR2);
sigwait(&mask_sig, &last_sig);
}
killpg(0, SIGUSR2);
file.close();
return 0;
}
Second child's code:
#include <iostream>
#include <fstream>
#include <unistd.h>
#include <cstring>
#include <sys/wait.h>
#include <signal.h>
#include <wait.h>
using namespace std;
int main(int argc, char** argv) {
int fildes[2];
fildes[0]=*argv[2];
fildes[1]=*argv[3];
close(fildes[1]);
sigset_t mask;
sigemptyset(&mask);
sigaddset(&mask, SIGQUIT);
sigset_t mask_sig;
sigemptyset(&mask_sig);
sigaddset(&mask_sig, SIGUSR2);
ofstream file;
int last_sig;
char ch;
file.open(argv[1], ios::app);
//sigwait(&mask, &last_sig);
sigwait(&mask_sig, &last_sig);
while(read(fildes[0], &ch, 1) > 0){
file << ch;
killpg(0, SIGUSR1);
sigwait(&mask_sig, &last_sig);
}
killpg(0, SIGUSR1);
file.close();
return 0;
}