How does getline work with cin?
I feel like there are a lot of similar questions, so I'm really sorry if this is a duplicate. I couldn't find the answer to this specific question, though.
I am confused as to how getline works when cin is passed to it, because my understanding is that it should be calling cin each time it is called. When working with code that was in a book I'm reading though, getline is called several times yet only one input is sent. The cin object is not called from anywhere except for within these getline calls.
What's going on here? When getline is reached does the program simply stop in its tracks and wait for the input stream to pass a value including the desired delimiter? If this is the case, do the subsequent getline calls just not have to wait because the input stream already has data including their respective delimiters? I ran a couple tests that would suggest this could be the case.
Here is the code:
string firstName;
getline(cin,firstName,',');
string lastName;
getline(cin,lastName,',');
string job;
getline(cin,job,'n');
cout<<firstName<<" "<<lastName<<" is a "<<job<<endl;;
Sorry again if this is a stupid question, but I looked around and genuinely could not find the answer. Thanks in advance for any help that can be provided!
Clarification:
This code outputs "First Last is a Job" for the console input "First,Last,Jobn"
A call to a function using cin is not actually a request for user input (at least not directly). It is a request for characters from the standard input. In normal program operation (where standard input is not being directed from a file or other source) standard input is stored in a buffer. If the standard input buffer is empty, and cin is requesting more characters, then your system will request input from the user via the terminal. (ie the keyboard). This input which the terminal requests is generally line oriented. That is, it waits for you to press the Enter key, then sends all the data to be stored in the standard input buffer. If cin gets all the characters it needs before the input buffer is empty, those characters remain until the next request.
So, for example, when you make this call:
getline(cin,firstName,',');
and the input buffer is empty, Let's say the user inputs this:
Benjamin, Lindley, Software DeveloperEnter
First, the following string is stored in the input buffer:
"Benjamin, Lindley, Software Developern"
Then getline causes "Benjamin," to be read from the input buffer (but discards the comma).
" Lindley, Software Developern"
remains in the buffer for any future operations with cin .
getline does not "call" cin at all. cin is an object. Objects contain data. The data in cin is the information needed by input functions to read the standard input stream. If you wanted to read from a file, for instance, you'd open the file and pass the file object to getline instead.
When getline is called, the program reads whatever is in the input buffer. If the input buffer already contains the delimiter then getline will return right away. Otherwise it will wait.
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