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BSD 2.11 - man page for lseek (bsd section 2)

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LSEEK(2)										 LSEEK(2)

NAME
       lseek - move read/write pointer

SYNOPSIS
       #include <sys/file.h>

       #define L_SET   0 /* set the seek pointer */
       #define L_INCR  1 /* increment the seek pointer */
       #define L_XTND  2 /* extend the file size */

       pos = lseek(d, offset, whence)
       off_t pos;
       int d;
       off_t offset;
       int whence;

DESCRIPTION
       The  descriptor	d refers to a file or device open for reading and/or writing.  Lseek sets
       the file pointer of d as follows:

	      If whence is L_SET, the pointer is set to offset bytes.

	      If whence is L_INCR, the pointer is set to its current location plus offset.

	      If whence is L_XTND, the pointer is set to the size of the file plus offset.

       Upon successful completion, the resulting pointer  location  as	measured  in  bytes  from
       beginning  of  the file is returned.  Some devices are incapable of seeking.  The value of
       the pointer associated with such a device is undefined.

NOTES
       Seeking far beyond the end of a file, then writing, creates a gap or "hole",  which  occu-
       pies no physical space and reads as zeros.

RETURN VALUE
       Upon  successful  completion,  the  current  file pointer value is returned.  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.

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

       [EINVAL]       Whence is not a proper value.

SEE ALSO
       dup(2), open(2)

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

4th Berkeley Distribution		February 24, 1986				 LSEEK(2)
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