.TH LSEEK 2 .SH NAME lseek, tell \- move read/write pointer .SH SYNOPSIS .B long lseek(fildes, offset, whence) .br .B long offset; .PP .B long tell(fildes) .SH DESCRIPTION The file descriptor refers to a file open for reading or writing. The read (resp. write) pointer for the file is set as follows: .IP If .I whence is 0, the pointer is set to .I offset bytes. .IP If .I whence is 1, the pointer is set to its current location plus .IR offset . .IP If .I whence is 2, the pointer is set to the size of the file plus .IR offset . .PP The returned value is the resulting pointer location. .PP The obsolete function .IR tell ( fildes ) is identical to .IR lseek ( "fildes, 0L, 1" ). .PP Seeking far beyond the end of a file, then writing, creates a gap or `hole', which occupies no physical space and reads as zeros. .SH "SEE ALSO" open(2), creat(2), fseek(3) .SH DIAGNOSTICS \-1 is returned for an undefined file descriptor, seek on a pipe, or seek to a position before the beginning of file. .SH BUGS .I Lseek is a no-op on character special files. .SH ASSEMBLER (lseek = 19.) .br (file descriptor in r0) .br .B sys lseek; offset1; offset2; whence .PP .I Offset1 and .I offset2 are the high and low words of .IR offset ; r0 and r1 contain the pointer upon return.