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@(#)lseek.2 4.1 (Berkeley) 05/09/85

C 4 lseek, tell - move read/write pointer

 long lseek(fildes, offset, whence)  long offset; 

 long tell(fildes) 

The file descriptor refers to a file open for reading or writing. The read (resp. write) pointer for the file is set as follows: If whence is 0, the pointer is set to offset bytes. If whence is 1, the pointer is set to its current location plus offset . If whence is 2, the pointer is set to the size of the file plus offset .

The returned value is the resulting pointer location.

The obsolete function tell ( fildes ) is identical to lseek ( "fildes, 0L, 1" ).

Seeking far beyond the end of a file, then writing, creates a gap or `hole', which occupies no physical space and reads as zeros.

open(2), creat(2), fseek(3) -1 is returned for an undefined file descriptor, seek on a pipe, or seek to a position before the beginning of file. Lseek is a no-op on character special files. (lseek = 19.)

(file descriptor in r0)

sys lseek; offset1; offset2; whence

Offset1 and offset2 are the high and low words of offset ; r0 and r1 contain the pointer upon return.