| LSEEK(2) | System Calls Manual | LSEEK(2) | 
lseek, seek —
#include <unistd.h>
off_t
  
  lseek(int
    fildes, off_t
    offset, int
    whence);
lseek() function repositions the offset of the file
  descriptor fildes to the argument
  offset according to the directive
  whence. The argument fildes must
  be an open file descriptor. lseek() repositions the
  file pointer fildes as follows:
SEEK_SET, the
      offset is set to offset bytes.SEEK_CUR, the
      offset is set to its current location plus offset
      bytes.SEEK_END, the
      offset is set to the size of the file plus offset
      bytes.The lseek() function allows the file
    offset to be set beyond the end of the existing end-of-file of the file. If
    data is later written at this point, subsequent reads of the data in the gap
    return bytes of zeros (until data is actually written into the gap).
Some devices are incapable of seeking. The value of the pointer associated with such a device is undefined.
lseek() returns the
  resulting offset location as measured in bytes from the beginning of the file.
  Otherwise, a value of -1 is returned and errno is set to
  indicate the error.
lseek() will fail and the file pointer will remain
  unchanged if:
lseek() function conforms to IEEE
  Std 1003.1-1990 (“POSIX.1”).
seek() function appeared in
  Version 1 AT&T UNIX, later renamed into
  lseek() for “long seek” due to a larger
  offset argument type.
| September 2, 2019 | NetBSD 10.0 |