用Pos和Copy配合使用。
eg:
function ReplaceWordFromFile(....):String;
var
mFs:TFileStream;
mOldWord:String;
mNewWord:String;
S,RS:String;
Begin
mFS:=TFileStream.Create(YourFileName,fmOpenRead);//Open the File
SetLength(S,mFS.Size);//Important
mFS.Read(PChar(S)^,mFS.Size);//Type Cast and Read the Content
RS:=Copy(S,1,Pos(mOldWord,S)-1);
RS:=RS+mNewWord;
RS:=RS+Copy(S,Pos(mOldWord,S)+Length(mOldWord),Length(S)-Pos(mOldWord,S)+Length(mOldWord)+1);
mFs.Free;
mFS:=TFileStream.Create(YourFileName,fmCreate);
mFS.Write(PChar(Result)^,Length(Result));//保存文件
mFS.Free;
end;