# lseek(2)

## NAME

         lseek - move read/write pointer

## SYNOPSIS

         #include <sys/types.h>
         #include <unistd.h>

         #define SEEK_SET     0      /* offset is absolute */
         #define SEEK_CUR     1      /* relative to current position */
         #define SEEK_END     2      /* relative to end of file */

         off_t lseek(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 SEEK_SET, the pointer is set to offset bytes.

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

              If whence is SEEK_END, 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 occupies 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

         fcntl(2), open(2).

## BUGS

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