查找并替换文件行

Question

I have a text file with over 12,000 lines. In that file I need to replace certain lines. Some lines begin with a ; , some have random words, some start with space. However, I am only concerned with the two types of lines I describe below.

I have a line like

  SET    avariable:0      ;Comments

and I need to replace it to look like

  set    aDIFFvariable:0      :Integer      // comments

The only CASE that is necessary is in the word Integer I needs to be capitalized.

I also have

  String aSTRING(7)      ;Comment

that needs to look like

  STRING aSTRING(7)           :array [0..7] of AnsiChar;      // Comments  

I need to keep all the spacing the same.

Here is what I have so far

static void Main(string[] args)
    {
        string text = File.ReadAllText("C:\\old.txt");
        text = text.Replace("old text", "new text");
        File.WriteAllText("C:\\new.txt", text);
    }

I think I need to use REGEX, which I have tried to make for my first example:

\\s\\s[set]\\s*{4}.*[:0]\\s*[;].* <-- I now know this is invalid - please advise

I need help with properly setting up my program to find and replace those lines. Should I read one line at a time and if it matches then do something? I am confused really as to where to start.

BRIEF pseudo code of what I want to do

//open file
//step through file
//if line == [regex] then add/replace as needed
//else, go to next line
//if EOF, close file

Answer 1

Taking a stab at this separately because each line is so radically different that capturing both in the same expression will be a nightmare.

To match your first example and replace it:

String input = "SET    avariable:0      ;Comments";
if (Regex.IsMatch(input, @"\s?(set)\s*(\w+):?(\d)\s+;?(.*)?"))
{
    input = Regex.Replace(input, @"\s?(set)\s*(\w+):?(\d)\s+;?(.*)?", "$1 $2:$3     :Integer // $4";
}

Give that a shot (Play with it here: http://regex101.com/r/zY7hV2 )

To match your second example and replace it:

String input = "String aSTRING(7)      ;Comments";
if (Regex.IsMatch(input, @"\s?(string)\s*(\w+)\((\d)\)\s*;(.*)"))
{
    input = Regex.Replace(input, @"\s?(string)\s*(\w+)\((\d)\)\s*;(.*)", "$1 $2($3) :array [0..$3] of AnsiChar; // $4";
}

And play around with this one here: http://regex101.com/r/jO5wP5