How can I use stringstream to keep a quotation mark in a string?

Question

I have a vector of strings that contain numbers, words, spaces, and even weird characters like quotation marks. I am trying to read it all in using a stringstream so I can separate the doubles from strings.

When I do this:

stringstream contains

4165 This package contains 12 1/2" Screws

Code:

stringstream >> mydouble 
stringstream >> mystring

mydouble contains

Then the only thing that gets read into mystring is

This package contains 12 1/2

How can I let it keep the entire line?

Sometimes my file contains this:

4165 This package contains 2 1/2" Screws

65 This package contains 12> 1/2" Screws

This package contains 1 screw

What is mystring's type? The way you have it, if that's a std::string or a char array, the only thing in there should be "This". — Benjamin Lindley
– Benjamin Lindley, Commented Jun 1, 2012 at 4:53

thb · Accepted Answer · 2012-06-01 05:00:35Z

3

Regrettably, the stream extraction operator >> is not good at the kind of thing you wish it to do. The right way to do what you want is to fetch the whole line by

std::getline(stringstream, myline);

then to write code to parse the line.

How to parse the line? Five options come to mind:

Write your own code to do it without relying on special tools.
Use Lex/Flex and Yacc/Bison.
Use Boost Spirit.
Use POSIX <regex.h>.
Use C++11 <regex> or TR1 <tr1/regex>.

None of these however is entirely trivial. If you want to know, for your application, I'd probably go with choice 1, choice 3 or choice 5. Whatever you choose to do, good luck to you.

If you don't know where to start, why don't you look up std::getline(), presented in <string>, and std::atoi(), presented in <cstdlib>? These should afford you some ideas as to where to go next.

edited Jun 1, 2012 at 5:00

answered Jun 1, 2012 at 4:54

thb

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1 Comment

thb Over a year ago

Correction: An earlier version of the answer referred to std::getline() as presented in <iostream>. That was the wrong header. There are two, distinct std::getline() functions in the standard library, and you want the other one, the one presented in <string>. I have corrected the answer above accordingly.

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