regress/sys/kern/write_append/write_append.c

   1 #include <err.h>
   2 #include <unistd.h>
   3 #include <fcntl.h>
   4
   5 static const char fn[] = "/tmp/write-test.txt";
   6 static const char str[] = "Test write() append\n";
   7 static size_t len = sizeof(str) - 1;
   8
   9 int
  10 main(void)
  11 {
  12         int fd;
  13         off_t off;
  14
  15         if ((fd = open(fn, O_CREAT | O_RDWR, 0600)) == -1)
  16                 err(1, "Cannot open `%s'", fn);
  17         if (write(fd, str, len) != (ssize_t)len)
  18                 err(1, "Write failed");
  19         if (close(fd) == -1)
  20                 err(1, "Close failed");
  21         if ((fd = open(fn, O_WRONLY | O_APPEND)) == -1)
  22                 err(1, "Cannot open `%s'", fn);
  23         if ((off = lseek(fd, (off_t) 0, SEEK_SET)) != (off_t)0)
  24                 err(1, "Seek failed");
  25         if (write(fd, str, 0) != 0)
  26                 err(1, "Write failed");
  27         if ((off = lseek(fd, (off_t) 0, SEEK_CUR)) != (off_t)0)
  28                 errx(1, "bad seek offset %lld\n", (long long)off);
  29         if (close(fd) == -1)
  30                 err(1, "Close failed");
  31         if (unlink(fn) == -1)
  32                 err(1, "Unlink failed");
  33         return 0;
  34 }