// Program:  breaknfs.c
//
// Compile:  cc breaknfs.c -o breaknfs
// Run:      ./breaknfs 100 [<nfs-mounted-dir>]
//
// Args:     arg1 = # of copies of program to run simultaneously
//           arg2 = A directory that is on an NFS-mounted filesystem

#define NFS_MOUNT	"/var/nfs"

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

#define BUFFER_SIZE (1*1024*1024)
static char buffer[BUFFER_SIZE];

int main(int argc, char *argv[])
{
	char*	nfs_dir;
	int	count;
	int	fd;
	int	i;
	int	pid;

	char *files[] = {"file1", "file2", "file3", "file4", "file5"};

	if (argc > 1)
		count = atoi(argv[1]);
	else
		count = 1;
	if (argc > 2)
		nfs_dir = argv[2];
	else
		nfs_dir = NFS_MOUNT;

	/* cd -> ... */
	if (chdir(nfs_dir) < 0) {
		perror(nfs_dir);
		exit(1);
	}

	/* Fill buffer with numbers and letters, etc! */
	for ( i = 0; i < BUFFER_SIZE; i++ ) {
		buffer[i] = '0' + (i & 0x3f);
		if ( i && ((i % 80) == 0) )
			buffer[i] = '\n';
	}

	/* fork count-1 children */
	while (count-- > 1) {
		pid = fork();
		if (pid == 0) {
			/* child */
			break;
		} else if (pid < 0) {
			perror("fork");
			exit(1);
		}
	}
	srandom(getpid());

        /* Forever and a day ... */
	while(1) {
		for (i = 0; i < 5; i++) {
			int	write_size;

                        /* Write a random amount of bytes, truncating file before output */
			write_size = (random() % BUFFER_SIZE) + 1;
			fd = open(files[i], O_WRONLY | O_CREAT | O_TRUNC, 0600);
			if (fd < 0) {
				perror("open");
				exit(1);
			}
			if (write(fd, buffer, write_size) < 0) {
				perror("write");
				exit(1);
			}
			close(fd);
		}
	}

	return 0;
}