Write File Example

Create an empty file sentences.txt, in case of failure print an error and exit. Do the following 100 times: call getSentence() to get new text in the buffer and its length, write the buffer to the file and record the number of bytes. If the number of written bytes is -1, print an error and exit. Close the file, output an error in case of failure.

writefile.c

#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <sys/time.h>
#include <string.h>
#define BUF_SIZE 1000000
long getMicrotime(){
        struct timeval currentTime;
        gettimeofday(&currentTime, NULL);
        return currentTime.tv_sec * (int)1e6 + currentTime.tv_usec;
}
int getSentence(char *buf) {
    sprintf(buf, "%ld> This is a new sentence.\n", getMicrotime());
    return strlen(buf);
}
int main(int argc, char *argv[])
{
    int fd;
    fd = open("./sentences.txt", O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (fd == -1)
    {
        printf("ERROR opening the file!\n");
        return -1;
    }
    char buf[BUF_SIZE];
    for (int i=0; i < 100; i++)
    {
        int text_len = getSentence(buf);
        ssize_t nr = write(fd, buf, text_len);
        if (nr == -1)
        {
            printf("ERROR writing to the file!\n");
            break;
        }
    }
    if (close(fd) == -1)
    {
        printf("ERROR closing the file!\n");
        return -2;
    }
    printf("SUCCESS!\n");
    return 0;
}