execNode in NodeRed doesn't execute a while 1 statement

Question

I'm running an exec node to run C code to send and receive data via Lora.

The code runs perfectly without a while 1 loop.

If I put a while true loop it will keep running but won't work. The while 1 is used to read data every second.

I tried using daemon exec node also bigExec but none worked.

Answer 1

If the process doesn't ever exit (which is what I assume you mean by having a while 1 loop) then the daemon node is the correct answer.

As long as your application prints it's output to stdout or stderr and includes a new line at the end of each output it will send a new message for each line of output. You might need to ensure that stdout is properly flushed, you can do this by adding fflush(stdout); after the printfs e.g.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char **argv) {
    int i = 0;
    int max = 0;

    if (argc == 2) {
        max = atoi(argv[1]);
    }

    while (1) {
        if (max) {
            if (++i > max) {
                exit(0);
            }
        }
        printf("helloWorld\n");
        fflush(stdout);
        sleep(2);
    }

}

The exec node will wait until the process exits before sending a message so is not not what you need.