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 fol-
     lows:

          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.