Strings and reading from files

[ahammad]

Hello,

I need to write a small console application that reads in individual lines of text from a specified file. Every line of text looks like this:

<CODE> = <COMMAND>

I want to be able to read in that line, split it in two at the equals sign (for all intents and purposes, the equals sign is just there to separate the text, kind of like a semicolon), and use the CSMapStringToString to store every command, with the code as the key.

What are ways to easily implement this?

Edit: my supervisor suggested that I use the CString class to get the data from the file...unfortunately he went on vacation and he won't be back to help me for another 3 weeks.

Also note that this isn't an assignment, it's for work. I jsut saw the student assignment thread and I thought I'll clarify this.

[AdrianH]

Use scanf("%<buffersize>[^=]= %<buffersize>[^\n]%*[\n\r]", left, right);
where <buffersize> is the size of the respective buffer.

The first will have an extra space at the end (you put a space between the equal sign and the left and right sides) that you may have to get rid of. If spaces are illegal on the left side add a space and other whitespace characters to the first character class. For more info, read up on scanf format strings.


Adrian

[weaknessforcats]

Try this:

ifstream input("record.txt");
string code;
string command;
char ch;
   //do this for each record of the file.
   while ((ch = input.get()) != '=')
   {
      code += ch;
   }
   while ((ch = input.get()) != '\n')
   {
      command += ch;
   }
 

If can use CString you are in C++. scanf() is for C.

[AdrianH]

Try this:

ifstream input("record.txt");
string code;
string command;
char ch;
   //do this for each record of the file.
   while ((ch = input.get()) != '=')
   {
      code += ch;
   }
   while ((ch = input.get()) != '\n')
   {
      command += ch;
   }
 

If can use CString you are in C++. scanf() is for C.

Oh come on wfc, CString is for if you want to limit yourself to a MFC framework. string is for general C++. You should know better. ;)

While I agree with your code (well under UNIX it would be fine but if you ran this under Windows or a Mac, you would either get a '\r' at the end of you command string or at the beginning of your code string), it is inefficient (not a problem if speed is not an issue and the file you have to parse is relatively small and not parsed often). The reason is that you are constantly reallocating memory each time you use the '+=' operator. This can also lead to memory fragmentation.

I've written a parsing document that can be looked at here. It is written for C (C++ has access to these functions as well). I will try and write one for C++ as well in the future.


Adrian

[ahammad]

Adrian, your way seems to work, but I guess something is wrong with my syntax. I'm still trying to figure it out.

I also tried the other way using CString, but once I type the filename, it seems to just stop running forever because I don't get a "done" message that I put in there.

Edit: I can't seem to figure out what I did wrong so here is the relevant output and code:

Adrian, I tried your method and this is what I end up with:

Please enter the filename: test.cpf
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
done
Press any key to continue . . .

Here are the relevant parts of the code that I used to do this:

char filename[100], code[999], command[999];
FILE *pFile;
 
pFile = fopen(filename, "r");
 
    for (int k = 0; k < 17; k++){
 
 
        fscanf(pFile, "%999[^=]= %999[^\n]%*[\n\r]", code, command);
 
        cout << code[k] << " = " << command[k] << endl;
}

What am I doing wrong here? Something tells me that I am not really understanding the <buffersize> that I should put in there.

Thanks

[AdrianH]

Adrian, I tried your method and this is what I end up with:

Please enter the filename: test.cpf
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
╠ = ╠
done
Press any key to continue . . .

Hmmm, well that doesn't look right. ;)

Here are the relevant parts of the code that I used to do this:

char filename[100], code[999], command[999];
FILE *pFile;
 
pFile = fopen(filename, "r");
 
    for (int k = 0; k < 17; k++){
 
 
        fscanf(pFile, "%999[^=]= %999[^\n]%*[\n\r]", code, command);
 
        cout << code[k] << " = " << command[k] << endl;
}

What am I doing wrong here? Something tells me that I am not really understanding the <buffersize> that I should put in there.

Thanks

Close make declaration code[1000], command[1000];, set the last element to '\0' in each and don't use indicies on code and command when outputing unless you ment to make code and command a 2d array. What you are telling it to do is output a character at index k, not the entire character string.


Adrian