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

int write_file ()
{
    FILE *file = fopen( "./testfile.txt", "w" );
    fprintf(file, "testtext\n123456");
    fclose( file );
    return 0;
}

int read_file ()
{
    FILE *file = fopen( "./testfile.txt", "r" );
    int character;
    while  ( ( character = fgetc( file ) ) != EOF )
    {
        printf( "%c", character );
    }
    printf("\n");
    fclose( file );
    return 0;
}

int lock()
{
    FILE *lockfile = fopen( "./lock.lck", "w" );
    fclose( lockfile );
    return 0;
}

int unlock()
{
    remove("./lock.lck");
    return 0;
}

int exist_file()
{
    FILE *fp = fopen ( "./lock.lck", "r");
    if (fp == NULL) { // file does not exist
        return 0;
    }
    else{
        return 1;
    }
}

int main ( int argc, char *argv[] )
{
    int i=0;
    pid_t npid; //variable for PID

npid = fork(); //fork parent process

//while(1){

    if(npid > 0){ //if parent process
    lock();
    write_file();
    i = exist_file();
    printf("return status = %d", i);
    printf("test");
    unlock();
    i = exist_file();
    }
    else if(npid == 0){ //if child process
    read_file();

    }
    else if(npid == -1){
        printf("ERROR");
    }

//  }
}