CODEWITHSUNDEEP
c#regex
JoseRivas1998
JoseRivas1998

Reputation: 553

Replace content in first set of quotes found in string c#

I am working on a project that involves having to manipulate a bat file based on certain user produced parameters. The bat files themselves are created manually, with a static format. A basic example of a bat file would be:

cd \some\predefined\bat
start run_some_script "user_generated_argument" [other pre-defined arguments]

The "user_generated_argument" bit of the bat file is manipulated in C# by the following code:

string bat_text = File.ReadAllText(bat_path);
Regex regex = new Regex("(.*?)\".*\"(.*)");
string new_argument = "A new argument";
string new_bat = regex.Replace(bat_text , "$1\"" + new_argument + "\"$2", 1);

And that would produce the following:

cd \some\predefined\bat
start run_some_script "A new argument" [other pre-defined arguments]

which is the expected output.

However, the problem lies when one of the other pre-defined arguments after the first quoted argument is also in quotes when that is the case, it seems that the second quoted argument disappears. For example, if the bat file looks like:

cd \some\predefined\bat
start run_some_script "user_generated_argument" "a_predefined_quoted_argument" [other pre-defined arguments]

Running the same C# code from above would produce the following:

cd \some\predefined\bat
start run_some_script "A new argument" [other pre-defined arguments]

The "a_predefined_quoted_argument" would no longer be in the string.

I may be doing this completely wrong. How would I make the predefined quoted argument not disappear?

Upvotes: 0

Views: 58

Answers (2)

nico boey
nico boey

Reputation: 389

the problem is that your expression \".*\" is eager or greedy, taking everything between the first quote and the last quote it finds. To make it lazy or reluctant, put a ? after the * like so (I used VB, which escapes double quotes by double double quotes)

Dim batfile As String = "cd \some\predefined\bat" & vbCrLf & "start run_some_script ""user_generated_argument"" ""a_predefined_quoted_argument"" [other pre-defined arguments]"
Dim regex As Regex = New Regex("(.*?)"".*?""(.*)")
Dim new_argument As String = "A new argument"
Dim new_bat As String = regex.Replace(batfile, "$1""" + new_argument + """ $2", 1)

It will now take everything between the first quote, and the next quote.

Upvotes: 1

Flurin
Flurin

Reputation: 129

Instead of using Regex you could also read the lines with File.ReadAllLines(), take the desired line and split it with string.Split() and replace them in that way.

Something like:

string[] lines = File.ReadAllLines(fileName);
string commandLine = lines.Where(d => d.StartsWith("start")).Single();
string[] arguments = commandLine.Split(' ');

foreach (var argument in arguments)
{
    if (argument.StartsWith("\""))
    {
        // do your stuff and reassemble
    }
}

Upvotes: 0

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