ceph/qa/workunits/fs/test_o_trunc.c

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

int main(int argc, char *argv[])
{
        int fd, ret;
        char obuf[32], ibuf[1024];
        int n, max = 0;

	if (argc > 2)
		max = atoi(argv[2]);
	if (!max)
		max = 600;

        memset(obuf, 0xff, sizeof(obuf));

        for (n = 1; n <= max; ++n) {
                fd = open(argv[1], O_RDWR | O_CREAT | O_TRUNC, 0644);
                printf("%d/%d: open fd = %d\n", n, max, fd);

                ret = write(fd, obuf, sizeof(obuf));
                printf("write ret = %d\n", ret);

                sleep(1);

                ret = write(fd, obuf, sizeof(obuf));
                printf("write ret = %d\n", ret);

                ret = pread(fd, ibuf, sizeof(ibuf), 0);
                printf("pread ret = %d\n", ret);

                if (memcmp(obuf, ibuf, sizeof(obuf))) {
                        printf("mismatch\n");
                        break;
                }
                close(fd);
        }
        return 0;
}