lseek(2) [redhat man page]

LSEEK(2)							   System calls 							  LSEEK(2)

NAME

       lseek - reposition read/write file offset

SYNOPSIS

       #include <sys/types.h>
       #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 as fol-
       lows:

       SEEK_SET
	      The offset is set to offset bytes.

       SEEK_CUR
	      The offset is set to its current location plus offset bytes.

       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).

RETURN VALUE

       Upon  successful completion, lseek returns the resulting offset location as measured in bytes from the beginning of the file.  Otherwise, a
       value of (off_t)-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.

CONFORMING TO

       SVr4, POSIX, BSD 4.3

RESTRICTIONS

       Some devices are incapable of seeking and POSIX does not specify which devices must support it.

       Linux specific restrictions: using lseek on a tty device returns ESPIPE.  Other systems return the  number  of  written	characters,  using
       SEEK_SET to set the counter.  Some devices, e.g. /dev/null do not cause the error ESPIPE, but return a pointer which value is undefined.

NOTES

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

       When converting old code, substitute values for whence with the following macros:

	old	  new
       0	SEEK_SET
       1	SEEK_CUR
       2	SEEK_END
       L_SET	SEEK_SET
       L_INCR	SEEK_CUR
       L_XTND	SEEK_END

       SVR1-3 returns long instead of off_t, BSD returns int.

       Note that file descriptors created by dup(2) or fork(2) share the current file position pointer, so seeking on such files may be subject to
       race conditions.

SEE ALSO

       dup(2), fork(2), open(2), fseek(3)

Linux								    2001-09-24								  LSEEK(2)

Check Out this Related Man Page

LSEEK(2)						      BSD System Calls 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 actually 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

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

     [EBADF]		Fildes is not an open file descriptor.

     [EINVAL]		Whence is not a proper value.

     [EINVAL]		The seek location (calculated from offset and whence) is negative.

     [EOVERFLOW]	The seek location is too large to be stored in an object of type off_t.

     [ESPIPE]		Fildes is associated with a pipe, socket, or FIFO.

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 IEEE Std 1003.1-1988 (``POSIX.1'').

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

Linux and UNIX Man Pages

lseek(2) [redhat man page]

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