lseek(2)lseek(2)NAMElseek - move read/write file pointer; seek
sets the file pointer associated with the file descriptor as follows:
· If whence is the pointer is set to offset bytes.
· If whence is the pointer is set to its current location plus
· If whence is the pointer is set to the size of the file plus
These symbolic constants are defined in
When completes successfully, it returns an integer, which is the
resulting file offset as measured in bytes from the beginning of the
file. Otherwise, a value of is returned and is set to indicate the
For all files that are not character or block special files, the inte‐
ger returned on successful completion is non-negative. For character
or block special files that correspond to disk sections larger than 2
gigabytes, a non-negative integer is returned for successful seeks
beyond 2 gigabytes. This value is the resulting file offset as mea‐
sured in bytes from the beginning of the file, when taken as an
unsigned value. always indicates an error return, even when encoun‐
tered on greater than 2 gigabyte disk sections. The call succeeds for
NFS directories even if the resulting file offset becomes negative.
fails and the file offset remains unchanged if one or more of the fol‐
lowing is true:
[EBADF] fildes is not an open file descriptor.
[ESPIPE] fildes is associated with a pipe, socket, or FIFO.
[EINVAL] whence is not one of the supported values.
[EINVAL] The resulting file offset would be negative.
[EINVAL] The resulting file offset would be a value which cannot
be represented correctly in an object of type
Some devices are incapable of seeking. The value of the file offset
associated with such a device is undefined.
Using with a whence of on device special files is not supported and the
results are not defined.
SEE ALSOcreat(2), dup(2), fcntl(2), lseek64(2), open(2), unistd(5).