projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| ec7838a8 KM |
1 | .\" Copyright (c) 1980 Regents of the University of California. |
| 2 | .\" All rights reserved. The Berkeley software License Agreement | |
| 3 | .\" specifies the terms and conditions for redistribution. | |
| 4 | .\" | |
| 5 | .\" @(#)lseek.2 4.1 (Berkeley) %G% | |
| 6 | .\" | |
| 7 | .TH LSEEK 2 | |
| 8 | .UC 4 | |
| 9 | .SH NAME | |
| 10 | lseek, tell \- move read/write pointer | |
| 11 | .SH SYNOPSIS | |
| 12 | .nf | |
| 13 | .B long lseek(fildes, offset, whence) | |
| 14 | .B long offset; | |
| 15 | .PP | |
| 16 | .B long tell(fildes) | |
| 17 | .fi | |
| 18 | .SH DESCRIPTION | |
| 19 | The file | |
| 20 | descriptor refers to a file open for reading or writing. | |
| 21 | The read (resp. write) pointer for the file is set as follows: | |
| 22 | .IP | |
| 23 | If | |
| 24 | .I whence | |
| 25 | is 0, the pointer is set to | |
| 26 | .I offset | |
| 27 | bytes. | |
| 28 | .IP | |
| 29 | If | |
| 30 | .I whence | |
| 31 | is 1, the pointer is set to its current location plus | |
| 32 | .IR offset . | |
| 33 | .IP | |
| 34 | If | |
| 35 | .I whence | |
| 36 | is 2, the pointer is set to the size of the | |
| 37 | file plus | |
| 38 | .IR offset . | |
| 39 | .PP | |
| 40 | The returned value is the resulting pointer location. | |
| 41 | .PP | |
| 42 | The obsolete function | |
| 43 | .IR tell ( fildes ) | |
| 44 | is identical to | |
| 45 | .IR lseek ( "fildes, 0L, 1" ). | |
| 46 | .PP | |
| 47 | Seeking far beyond the end of a file, then writing, | |
| 48 | creates a gap or `hole', which occupies no | |
| 49 | physical space and reads as zeros. | |
| 50 | .SH "SEE ALSO" | |
| 51 | open(2), creat(2), fseek(3) | |
| 52 | .SH DIAGNOSTICS | |
| 53 | \-1 | |
| 54 | is returned for | |
| 55 | an undefined file descriptor, | |
| 56 | seek on a pipe, | |
| 57 | or seek to a position before the beginning of file. | |
| 58 | .SH BUGS | |
| 59 | .I Lseek | |
| 60 | is a no-op on character special files. | |
| 61 | .SH "ASSEMBLER (PDP-11)" | |
| 62 | (lseek = 19.) | |
| 63 | .br | |
| 64 | (file descriptor in r0) | |
| 65 | .br | |
| 66 | .B sys lseek; offset1; offset2; whence | |
| 67 | .PP | |
| 68 | .I Offset1 | |
| 69 | and | |
| 70 | .I offset2 | |
| 71 | are the high and low words of | |
| 72 | .IR offset ; | |
| 73 | r0 and r1 contain | |
| 74 | the pointer upon return. |