LSEEK(2)            Linux Programmer's Manual            LSEEK(2)


NAME
       lseek - reposition read/write file offset

SYNOPSIS
       #include <unistd.h>

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

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 actu-
       ally written into the gap).

       Some devices are incapable of seeking.  The value  of  the
       pointer associated with such a device is undefined.

RETURN VALUES
       Upon  successful  completion,  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.

ERRORS
       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.

CONFORMS TO
       POSIX, BSD 4.3

BUGS
       This  document's  use  of whence is incorrect English, but
       maintained for historical reasons.





Linux 1.2.9                10 June 1995                         1





LSEEK(2)            Linux Programmer's Manual            LSEEK(2)

SEE ALSO

dup, open, fseek,

Linux 1.2.9                10 June 1995                         2