FreeBSD Man Pages

lseek(2)

NAME

     lseek -- reposition read/write file offset

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

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

DESCRIPTION

     The lseek() system call 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.  The lseek() system call
     repositions the file position pointer associated with the file descriptor
     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() system call 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.

ERRORS

     The lseek() system call will fail and the file position pointer will
     remain unchanged if:

     [EBADF]		The fildes argument is not an open file descriptor.

     [EINVAL]		The whence argument is not a proper value or the
			resulting file offset would be negative for a non-
			character special file.

     [EOVERFLOW]	The resulting file offset would be a value which can-
			not be represented correctly in an object of type
			off_t.

     [ESPIPE]		The fildes argument is associated with a pipe, socket,
			or FIFO.

     The lseek() system call is expected to conform to ISO/IEC 9945-1:1990
     (``POSIX.1'').

HISTORY

     The lseek() function appeared in Version 7 AT&T UNIX.

FreeBSD 5.4			April 19, 1994			   FreeBSD 5.4

SPONSORED LINKS