Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
LSEEK(2)		  FreeBSD System Calls Manual		      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() 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
     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() 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.

ERRORS
     Lseek() will fail and the file position 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 call is expected to conform to ISO/IEC 9945-1:1990
     (``POSIX.1'').

HISTORY
     A lseek() function	call appeared in Version 7 AT&T	UNIX.

FreeBSD	9.3			April 19, 1994			   FreeBSD 9.3

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | BUGS | STANDARDS | HISTORY

Want to link to this manual page? Use this URL:
<http://www.freebsd.org/cgi/man.cgi?query=lseek&sektion=2&manpath=FreeBSD+4.6-RELEASE>

home | help