I have multithread applications. In one thread I want to waiting for data, and if this datas will not appear through some time, I just close whole application. Function select() is runs in another thread and thread is detach
A piece sorce some class
#define STDIN 0
A::A(){
runFunction1();
runFunction2();
thread listen(&A::isData , this);
listen.detach();
}
// and function with select
void A::isData{
struct timeval tv;
fd_set readfds;
tv.tv_sec = 50; // wait to 50 seconds
tv.tv_usec = 500000;
FD_ZERO(&readfds);
FD_SET(STDIN, &readfds);
for(;;) {
select(STDIN+1, &readfds, NULL, NULL, &tv);
if (FD_ISSET(STDIN, &readfds)){
cout << "I something catch :)" << endl;
// reset time
}else{
cout << "I nothing catch ! By By :(" << endl;
exit(1);
break;
}
}
}
If my program run then I get pid, so I have tryed write to file descriptor some datas in below way:
$ cd /proc/somePID/fd
$ echo 1 >> 0
Then I should be get info I something catch :) but in console IDE I only get 1 , however if time is out I get I nothing catch ! By By :( to console in IDE.
EDIT: SOLVED
@Vladimir Kunschikov gave me correct tip. Basic on this I show how I do it in C/C++
It will be posible send something to process using command echo we must create pipe. Pipe using function
A::A(){
fd[2]; //two file descriptor for pipes write/read
pipe(fd); // c function to create pipes
runFunction1();
runFunction2();
thread listen(&A::isData , this);
listen.detach();
}
Then in our proces will create other two new file descriptor as below:
lrwx------ 1 user user 64 gru 15 14:02 0 -> /dev/pts/0
lrwx------ 1 user user 64 gru 15 14:02 1 -> /dev/pts/0
lrwx------ 1 user user 64 gru 15 14:02 2 -> /dev/pts/1
lr-x------ 1 user user 64 gru 15 14:02 3 -> pipe:[1335197]
lrwx------ 1 user user 64 gru 15 14:02 4 -> socket:[1340788]
l-wx------ 1 user user 64 gru 15 14:02 5 -> pipe:[1335197]
pipe:[1335197] is descriptor to read in this proces. Now command echo will be works if we will write some to descriptor 3. Using is simply:
$ cd /proc/PID/fd
$ echo 1 > 3
Then we also can using this in select() function but descriptor number is 3 so define should be looks like .
#define STDIN 3
And works
