nbsp; Rewrite(F);
Write(F,Rec);
Rec.pp_No:=''''0002'''';
Rec.pp_Sum:=58.2;
Write(F,Rec);
Rec.pp_No:=''''0003'''';
Rec.pp_Sum:=258.242;
Write(F,Rec);
seek(F,1);
Read(F,Rec2);
seek(F,1);
Truncate(F); {删除,只剩第0笔}
Canvas.TextOut(5,10,Rec2.pp_No);
Canvas.TextOut(5,30,Rec2.pp_Name);
Canvas.TextOut(5,50,Format(''''%d'''',[Rec2.pp_Age]));
Canvas.TextOut(5,70,Format(''''%f'''',[Rec2.pp_Sum]));
CloseFile(F);
end;
结果 pp_No存入6 Bytes
pp_Name存入11 Bytes
pp_Age存入4 Bytes(Integer 4 Bytes)
pp_Sum存入8 Bytes(Double 8 Bytes)
整个Record以16的倍数存档.
EXAMPLE
var F: TextFile;
begin
AssignFile(F, ''''NEWFILE.$$$'''');
Rewrite(F);
Writeln(F, ''''Just created file with this text in it...'''');
CloseFile(F);
end;
-----------------------------------------------------------------------------
Seek 移动档案指标.
-----------------------------------------------------------------------------
Unit System
函数原型 procedure Seek(var F; N: Longint);
说明 Seek从0开始.
Example
var
f: file of Byte;
size : Longint;
S: string;
y: Integer;
begin
if OpenDialog1.Execute then
begin
AssignFile(f, OpenDialog1.FileName);
Reset(f);
size := FileSize(f);
S := ''''File size in bytes: '''' + IntToStr(size);
y := 10;
Canvas.TextOut(5, y, S);
y := y + Canvas.TextHeight(S) + 5;
S := ''''Seeking halfway into file...'''';
Canvas.TextOut(5, y, S);
y := y + Canvas.TextHeight(S) + 5;
Seek(f,size div 2);
S := ''''Position is now '''' + IntToStr(FilePos(f));
Canvas.TextOut(5, y, S);
CloseFile(f);
end;
end;
## FileSize, Seek, FilePos Example
-----------------------------------------------------------------------------
Truncate 将目前档案指标位置之後的档案内容全部删除.
-----------------------------------------------------------------------------
Unit System
函数原型 procedure Truncate(var F);
范例
var
f: file of Integer;
i,j: Integer;
begin
AssignFile(f,''''TEST.INT'''');
Rewrite(f);
for i := 1 to 6 do
Write(f,i);
Writeln(''''File before truncation:'''');
Reset(f);
while not Eof(f) do
begin
Read(f,i);
Writeln(i);
end;
Reset(f);
for i := 1 to 3 do
Read(f,j); { Read ahead 3 records }
Truncate(f); { Cut file off here }
Writeln;
Writeln(''''File after truncation:'''');
Reset(f);
while not Eof(f) do
begin
Read(f,i);
Writeln(i);
end;
CloseFile(f);
Erase(f);
end;
-----------------------------------------------------------------------------
FilePos 传回目前档案的位置.
-----------------------------------------------------------------------------
Unit System
函数原型 function FilePos(var F): Longint
说明 F 不可为 Text File
档头 :FilePos(F):=0;
档尾 :Eof(F):=True;
范例 var
f: file of Byte;
S: string;
begin
S:= ''''c:\ka\abc.txt'''';
AssignFile(f, S);
Reset(f);
Seek(f,1);
Label1.Caption := ''''现在位置 : '''' + IntToStr(FilePos(f));
end;
Example
var
f: file of Byte;
size : Longint;
S: string;
y: Integer;
begin
if OpenDialog1.Execute then
begin
AssignFile(f, OpenDialog1.FileName);
Reset(f);
size := FileSize(f);
S := ''''File size in bytes: '''' + IntToStr(size);
y := 10;
Canvas.TextOut(5, y, S);
y := y + Canvas.TextHeight(S) + 5;
S := ''''Seeking halfway into file...'''';
Canvas.TextOut(5, y, S);
y := y + Canvas.TextHeight(S) + 5;
Seek(f,size div 2);
S := ''''Position is now '''' + IntToStr(FilePos(f));
Canvas.TextOut(5, y, S);
CloseFile(f);
end;
end;
##FileSize, Seek, FilePos Example
-----------------------------------------------------------------------------
FileSize 档案长度.
-----------------------------------------------------------------------------
Unit System
函数原型 function FileSize(var F): Integer;
说明 F 不可为 Text File
如果F为record file,则传回record数,
否则传回Byte数.
## FileSize, Seek, FilePos Example
-----------------------------------------------------------------------------
Eof 测试档案是否结束.
-----------------------------------------------------------------------------
Unit System
函数原型 function Eof(var F): Boolean;
函数原型 function Eof [ (var F: Text) ]: Boolean;
范例 var
F1, F2: TextFile;
Ch: Char;
begin
if OpenDialog1.Execute then
begin
AssignFile(F1, OpenDialog1.Filename);
Reset(F1);
if SaveDialog1.Execute then
begin
AssignFile(F2, OpenDialog1.Filename);
Rewrite(F2);
while not Eof(F1) do
begin
Read(F1, Ch);
Write(F2, Ch);
end;
CloseFile(F2);
end;
CloseFile(F1);
end;
end;
Example
var
F1, F2: TextFile;
Ch: Char;
begin
if OpenDialog1.Execute then begin
AssignFile(F1, OpenDialog1.Filename);
Reset(F1);
if SaveDialog1.Execute then begin
AssignFile(F2, SaveDialog1.Filename);
Rewrite(F2);
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