pwrite.c

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

#define BLOCK_SIZE 524288

int main(int argc, char **argv) {
        int64_t s, off;
        char *data;
        int64_t fd, rc, i;

        data = (char *) malloc(sizeof(char) * BLOCK_SIZE);
        if (!data) {
                rc = 2;
                goto err;
        }

        memset(data, 'b', BLOCK_SIZE);

        rc = 0;
        for (i=0; i < 10000; i++) {
                fd = open("/var/lib/mysql/plain_pwrite.werr", O_CREAT | O_RDWR);
                if (fd < 0) {
                        rc = 1;
                        goto err;
                }

                off = lseek(fd, 0, SEEK_END);
                s = pwrite(fd, data, BLOCK_SIZE, off);

                printf("wrote %lld bytes, file offset %lld\n", s, off);

                s = fsync(fd);
                printf("fsync success %lld\n", s);
                close(fd);
        }

err:
        close(fd);
        return rc;
}