题
有没有办法检查Delphi中的ReWrite是否已打开文件?
代码会是这样的:
AssignFile(textfile, 'somefile.txt');
if not textFile.IsOpen then
Rewrite(textFile);
解决方案
您可以获取文件模式。 (有一刻,我会创建一个例子)。
TTextRec(txt).Mode为您提供模式:
55216 = closed
55217 = open read
55218 = open write
fmClosed = $D7B0;
fmInput = $D7B1;
fmOutput = $D7B2;
fmInOut = $D7B3;
在系统单元中搜索TTextRec以获取更多信息。
其他提示
试试这个:
function IsFileInUse(fName: string) : boolean;
var
HFileRes: HFILE;
begin
Result := False;
if not FileExists(fName) then begin
Exit;
end;
HFileRes := CreateFile(PChar(fName)
,GENERIC_READ or GENERIC_WRITE
,0
,nil
,OPEN_EXISTING
,FILE_ATTRIBUTE_NORMAL
,0);
Result := (HFileRes = INVALID_HANDLE_VALUE);
if not(Result) then begin
CloseHandle(HFileRes);
end;
end;
这很好用:
function IsOpen(const txt:TextFile):Boolean;
const
fmTextOpenRead = 55217;
fmTextOpenWrite = 55218;
begin
Result := (TTextRec(txt).Mode = fmTextOpenRead) or (TTextRec(txt).Mode = fmTextOpenWrite)
end;
I found it easier to keep a boolean variable as a companion; example: bFileIsOpen
. Wherever the file is opened, set bFileIsOpen := true
then, whenever you need to know if the file is open, just test this variable; example: if (bFileIsOpen) then Close(datafile);
Joseph's answer works perfectly - I called the function filenotopen
and changed the line if
Result := (HFileRes = INVALID_HANDLE_VALUE);
to
Result := NOT (HFileRes = INVALID_HANDLE_VALUE);
I also removed the line 'if not(Result) then begin' (and the 'end') so that it ALWAYS closes the handle or subsequent assignments and reads give errors
I now call it like this
if filenotopen(filename) then
begin
assignfile(f,filename);
reset(f)
etc;
end
else
message('file open by a different program')
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