CODEWITHSUNDEEP
c#.net
nxfi777
nxfi777

Reputation: 91

Directory string interpolation for file creation

I have created something that has flash drive insertion and removal events to generate a key to use for a USB drive authenticator.

Everything works perfectly upto when I try to create the key, I can't seem to interpolate the drive label.

string BID = Sys.GetBaseboardID();
string CID = Sys.GetMachineGuID();
string k = "32 char string"; // this is where my 256 bit key goes
string iv = "16 char string"; // this is where my 128 bit key goes
string bencr = AES.Encrypt(BID, k, iv); //sorry for my strange variable names
string cencr = AES.Encrypt(CID, k, iv);
string keydir = "{dName}:\b4nk.key"; // <-- Here is the problem

StreamWriter w_r;
w_r = File.CreateText(@keydir);
w_r.WriteLine("WARNING: TOUCHING THIS FILE WILL REMOVE YOUR AUTHENTICATION\n");
w_r.WriteLine(bencr);
w_r.WriteLine(cencr);
w_r.Close();
File.SetAttributes(@keydir, FileAttributes.Hidden | FileAttributes.ReadOnly);

As you can most likely imagine, the output of the keydir string is the following: {dName}:4nk.key

There are a couple problems:

  1. \b seems to act similarly to \n (I assume it is used for 'break' or something)
  2. I need it to be a directory, so it requires the @ character at the start.
  3. If I try to do something like: string keydir = dName + ":\b4nk.key" although it works, the \b problem remains.

Solution

thanks to @Joshua Robinson I have learned something really interesting, my recent usage of python had me confused here.

to fix this you can combine the $ and @ characters to get an interpolated, verbatim string literal:

string keydir = $@"{dName}:\b4nk.key";

Upvotes: 2

Views: 1337

Answers (3)

MakePeaceGreatAgain
MakePeaceGreatAgain

Reputation: 37113

You´re mixing two things here: string-interpolation and a verbatim string.

The first one is indicated using the $ infront:

var myString = $"{ data }whateverComesNext";

The verbatim simply escapes any slahes. As you already assumed \b is an escape-sequence. You have to escape that sequence, e.g. by using \\b. Alternativly use both verbatim and interpolation:

var myString = $@"{ data }\banyothertext"`.

Upvotes: 2

Joshua Robinson
Joshua Robinson

Reputation: 3547

Check out the documentation on string interpolation.

The $ special character identifies a string literal as an interpolated string. An interpolated string is a string literal that might contain interpolation expressions. When an interpolated string is resolved to a result string, items with interpolation expressions are replaced by the string representations of the expression results. This feature is available starting with C# 6.

So, in order to get an interpolated string, your string literal needs to begin with the $ character.

string keydir = $"{dName}:\b4nk.key";

You should also check out the documentation on verbatim strings. Specifically, the second item in the list which describes verbatim string literals.

To indicate that a string literal is to be interpreted verbatim. The @ character in this instance defines a verbatim string literal. Simple escape sequences (such as "\" for a backslash), hexadecimal escape sequences (such as "\x0041" for an uppercase A), and Unicode escape sequences (such as "\u0041" for an uppercase A) are interpreted literally. Only a quote escape sequence ("") is not interpreted literally; it produces one double quotation mark. Additionally, in case of a verbatim interpolated string brace escape sequences ({{ and }}) are not interpreted literally; they produce single brace characters. The following example defines two identical file paths, one by using a regular string literal and the other by using a verbatim string literal. This is one of the more common uses of verbatim string literals.

It appears you've added the special @ character to the name of your variable, keydir. Using the @ character at the beginning of a variable name would allow you to use a keyword as a variable name, for example if you wanted a variable named class you could name it @class. Placing @ at the start of the variable name will not cause it to be interpreted literally if it is a string, you have to place it at the front of the string literal.

You can combine the $ and @ characters to get an interpolated, verbatim string literal:

string keydir = $@"{dName}:\b4nk.key";

Upvotes: 2

dommilosz
dommilosz

Reputation: 127

If you mean to have in file {dName}:\b4nk.key not {dName}:4nk.key you can replace all '\' chars to '\\'. \ breaks another \ and it remains \ but without it's function or simply add @ before string

string a = "asdak\\nsa\\b"

Or string a = @"asdak\nsa\b";

I hope it helps

Upvotes: -1

Related Questions