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

#define BUFSIZE 1024
#define MSG_STR "Hello World\n"

int main(int argc, char *argv[])
{
    int            fd = -1;
    int            rv = -1;
    char           buf[BUFSIZE];

    fd=open("test.txt", O_RDWR|O_CREAT|O_TRUNC, 0666);
    if(fd < 0)
    {
        perror("Open/Create file test.txt failure");
        return 0;
    }
    printf("Open file returned file descriptor [%d]\n", fd);

    if( (rv=write(fd, MSG_STR, strlen(MSG_STR))) < 0 )
    {
        printf("Write %d bytes into file failure: %s\n", rv, strerror(errno));
        goto cleanup;
    }

    //memset(buf, 0, sizeof(buf));
    if( (rv=read(fd, buf, sizeof(buf))) < 0 )
    {
        printf("Read data from file failure: %s\n", strerror(errno));
        goto cleanup;
    }

    printf("Read %d bytes data from file: %s\n", rv, buf);

cleanup:
    close(fd);
    
    return 0;
}