RTEMS 4.7.99.2 On-Line Library

Input and Output Primitives Manager lseek - Reposition read/write file offset

RTEMS POSIX API User's Guide

5.4.8: lseek - Reposition read/write file offset

CALLING SEQUENCE:

#include <sys/types.h>
#include <unistd.h>

int lseek(
  int    fildes,
  off_t  offset,
  int    whence
);

STATUS CODES:

EBADF: Fildes is not an open file descriptor.
ESPIPE: Fildes is associated with a pipe, socket or FIFO.
EINVAL: Whence is not a proper value.

DESCRIPTION:

The 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:

If whence is SEEK_SET, the offset is set to offset bytes.
If whence is SEEK_CUR, the offset is set to its current location plus offset bytes.
If whence is 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.

NOTES:

NONE

RTEMS POSIX API User's Guide