test if FS is concurrent

main.c

#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<unistd.h>
#include<stdio.h>

// 100mB
#define N 104857600

char *buf[N] = {0};

int main(int argc, char **argv) {
  int fd = open(argv[1], O_CREAT | O_TRUNC | O_RDWR, 0644);

  // let it time to start up
  sleep(1);

  printf("before write")
  write(fd, buf, N);
  close(fd);
}

start.sh

#!/bin/bash

./my_file "./file1.txt" &
./my_file "./file2.txt" &