suzanne.soy/racket
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

docs: correct description of file-position

Browse Source 
Explain more when a file's size is changed by `file-position`.
This commit is contained in:
Matthew Flatt 2019-06-24 15:28:22 -06:00
parent 0d3d0d7d86
commit 87673902dc
1 changed files with 10 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
pkgs/racket-doc/scribblings/reference/port-buffers.scrbl
View File

@ -99,11 +99,16 @@ called with a position argument on such a @tech{file-stream port}, the
@exnraise[exn:fail:filesystem]. @exnraise[exn:fail:filesystem].
When @racket[file-position] sets the position @racket[pos] beyond the When @racket[file-position] sets the position @racket[pos] beyond the
current size of an output file or (byte) string, the file/string is enlarged current size of an output file or (byte) string, the file/string is
to size @racket[pos] and the new region is filled with @racket[0] enlarged to size @racket[pos] and the new region is filled with
bytes. If @racket[pos] is beyond the end of an input file or (byte) string, @racket[0] bytes; in the case of a file. In the case of a file output
then reading thereafter returns @racket[eof] without changing the port, the file might not be enlarged until more data is written to the
port's position. file; in that case, beware that writing to a file opened in
@racket['append] mode on Unix and Mac OS will reset the file pointer
to the end of a file @emph{before} each write, which defeats file
enlargement via @racket[file-position]. If @racket[pos] is beyond the
end of an input file or (byte) string, then reading thereafter returns
@racket[eof] without changing the port's position.
When changing the file position for an output port, the port is first When changing the file position for an output port, the port is first
flushed if its buffer is not empty. Similarly, setting the position flushed if its buffer is not empty. Similarly, setting the position