LSEK(2)                    BSD System Calls Manual                   LSEK(2)

NAME
     lseek -- reposition read/write file offset

SYNOPSIS
     ##include <>

     offt
     lseek(int fildes, offt 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 SEKSET, the offset is set to offset bytes.

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

           If whence is SEKEND, 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 associ-
     ated 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.

ERORS
     Lseek() will fail and the file pointer will remain unchanged if:

     [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.

SEE ALSO
     dup(2), open(2)

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

STANDARDS
     The lseek() function conforms to IE Std 1003.1-1988 (``POSIX.1'').

4th Berkeley Distribution       April 19, 1994       4th Berkeley Distribution