Splitting C strings using a Delimiter-CodePudding

Okay, So I've looked around on StackOverflow and I've stumbled across a way of splitting C via delimiters.

So far, I've looked at these, and I still don't understand it.

From my understanding, I need to use a delimiter, using a variable that houses the delimiter, and then use the substr() method/function, but I don't understand the whole thing.

For instance, I saw this one example where it was referencing pos and npos, I don't understand that. And my other issue is, I wouldn't know how to do it with a string with multiple copies of the same delimiter.

My goal is to take a date like this: "29/01/2022 • 05:25:01" to split it into a struct for date and time, eg:

struct Date
{
    int day;           //Integer for days
    int month;         //Integer for months
    int year;          //Integer for years
};

struct Time 
{
    int hour;           //Integer for hour of drop
    int minute;         //Integer for minute of drop
    int second;         //Integer for second of drop
    int milisecond;     //Integer for milisecond of drop
};

I've also looked at https://www.cplusplus.com/reference/, however I want to split it up so that they are stored in their own variables, eg:

string example
{
    struct Date D;
    struct Time T;

    D.Day = 29;
    D.Month = 01;
    D.Year = 2022;

    T.Hour = 5;
    T.Minute = 25;
    T.Second = 01;
}

Would someone be able to explain this to me in a simpler way, or show me a source that explains it easier? The main problem I have is not understanding certain words.

Any help is appreciated, I really am trying to learn, but I don't quite understand these subjects yet.

CodePudding user response：

Let's go step by step, starting with the date:

29/01/2022  -- Day, Month, Year.

Given the following:

unsigned int day = 0u;
std::cin >> day;

The input of an integer skips whitespace until the first number character (for the first number character, also includes ' ' and '-'). The extraction operator keeps reading characters, building a number, until a non-numeric character is reached:

2 --> day. 9 --> day.

The next character is '/', which is not a numeric character so the extraction operator returns the number 29.

The character '/' in this context is known as a delimiter, because it separates the day field from the month field.
Since it's a character, it has to be read using a character variable:

char delimiter = '\0';  
std::cin >> delimiter;

Now, the delimiter is no longer in the buffer. You can check the content of the delimiter variable or move on.

Reading the month is similar:

unsigned int month = 0U;
std::cin >> month;

Edit 1: delimiter and substrings
You could extract the month as a string using a delimiter:

std::string month_as_text;
std::getline(std::cin, month_as_text, '/');

The getline function above reads characters from std::cin, placing into the string month_as_text, until it finds the delimiter character '/'. You can then convert month_as_text into an integer variable.