17 replies to this topic

[jasonalien]

Hi. I need to read a text file which is divided line by line and the lines are divided by 5 tabspaces. I need to group the parts between tabspaces. How can I read this kind of file tab by tab and line by line

[Orjan]

I suggest you read line by line and deal with the tabs per line

[gregwarner]

strtok(str, "\t") will be useful to you here.

[kernelcoder]

Yeah, if you are working with C, you can use strtok.

But if you are working with C++, you can use getline method to get a line and to parse all the string in a line you can use istringstream class. Here is a hint.

ifstream file("example.txt");

if (file.is_open()) {
  while (!file.eof() ) {
    string line;
    getline (file,line); // reads a line
    cout << line << endl;
    istringstream iss(line);
    do {
       string sub;
       iss >> sub; // parting the each string in the line
       cout << "part-string: " << sub << endl;
    } 
    while (iss);
  }
  file.close();
}

[jasonalien]

Well I succeeded in reading line by line, now I need to extract the 3rd and 4th elements in the string. The elements are seperated by tabs. There are are 6 elements in total per line. Can you help me with that please?

I'm coding in C and the other elements are not used.

[gregwarner]

Look at the documentation for strtok:
http://cplusplus.com...cstring/strtok/

In the first call to strtok, you pass in your string pointer and a literal string containing your delimiters (\t in your case). Then, every subsequent call to strtok, while passing in null instead of your string pointer, will return the next token in the string. strtok returns null when there are no more tokens in the string to parse.

If you want to retrieve specific tokens in the string by their position, I would suggest implementing a while loop like the example code does in the documentation above, but also keep and increment an index variable each time the loop runs, and use that variable to store the parsed token into an array of string pointers. This way, each time the loop iterates, it points the next string pointer in your array to the next token. When you're all done, the 3rd and 4th elements will be accessible through the pointers at the array indices 2 and 3, respectively.

[dargueta]

What are you using, C or C++? It dramatically changes the answer.

[jasonalien]

I'm using C++

[dargueta]

In that case don't use strtok(). Can your file contain regular spaces in the fields as long as the fields are separated by tabs?

[jasonalien]

the file is like this:
word1--tab--word2--tab--word3--tab--word4--tab--word5--newline
word1--tab--word2--tab--word3--tab--word4--tab--word5--newline
word1--tab--word2--tab--word3--tab--word4--tab--word5--newline

[dargueta]

So the words cannot contain spaces? In that case, do as kernelcoder suggested.

[jasonalien]

words don't contain any spaces