Iterating over lines in a string?

Question

I am trying to do something like this:

BOOST_FOREACH (const std::string& line, allLinesOf(someFileLoadedIntoString))
{
   ...
}

I wonder how to implement the allLinesOf function? Thanks!

UPDATE: Thanks for the answers. Sorry but I forgot to mention one important detail: in my case the newlines are \r\n.

Duplicate of [Is there a C++ iterator that can iterate over a file line by line?](http://stackoverflow.com/questions/2291802/is-there-a-c-iterator-that-can-iterate-over-a-file-line-by-line) (though, Jerry's answer to [How do I iterate over `cin` line by line in C++?](http://stackoverflow.com/questions/1567082/how-do-i-iterate-over-cin-line-by-line-in-c) is better than that exact duplicate). — James McNellis, Nov 21 '10 at 17:16

score 5 · Accepted Answer · edited Jul 25 '17 at 18:04

5

You can use std::getline.

std::string line;
while(std::getline(file, line)) {
    // Ohai!
}

edited Jul 25 '17 at 18:04

craymichael

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answered Nov 21 '10 at 17:24

Puppy

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Will it work with "\r\n" newlines? The string is loaded from a text file on Windows. – Alex Jenter Nov 21 '10 at 18:28
@Alex: You can specify a separator, from memory, and in addition, I believe that the MSVC STL automatically converts "\r\n" to "\n" when loading in text mode. – Puppy Nov 21 '10 at 18:31
2

The I/O Streams library performs newline translation, so when you open a file stream in text mode, it will automatically translate the platform line ending (which may be `\r\n` or something else) into the C++ line ending (`\n`). – James McNellis Nov 22 '10 at 03:25

score 2 · Answer 2 · answered Nov 21 '10 at 17:16

2

Um, you can write a custom iterator for std::string that would iterate over string segments separated by newlines and pass a std::pair of such iterators to BOOST_FOREACH

answered Nov 21 '10 at 17:16

Kirill V. Lyadvinsky · Answer 3 · 2010-11-21T17:37:08.457

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You can use boost::tokenizer with \n token to iterate over lines.

edited Nov 21 '10 at 17:37

answered Nov 21 '10 at 17:16

Kirill V. Lyadvinsky

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Would it be possible to pack it into one allLinesOf function? – Alex Jenter Nov 21 '10 at 17:18
Might not be a good idea in some cases. Look here: http://www.codinghorror.com/blog/2010/01/the-great-newline-schism.html – Aamir Nov 21 '10 at 17:23
Or BOOST_FOREACH in conjunction with boost::split :) – asdfjklqwer Nov 21 '10 at 17:34
@Aamir, `\n` in not necessarily is `0x0A`. The Standard guarantees that `\n` is the line end independently of the OS used. – Kirill V. Lyadvinsky Nov 21 '10 at 17:41

Iterating over lines in a string?

3 Answers3