Replace line breaks in a STL string

Question

How can I replace \r\n in an std::string?

Um. What do you want to replace them with? And, maybe a little context would help, no? — dmckee --- ex-moderator kitten, Jan 27 '09 at 17:03
As @dmckee---ex-moderatorkitten says: the code can be a lot simpler, if you only intend to replace it with a string of length less than or equal to the original. — user2023370, Feb 11 '23 at 14:48

score 31 · Answer 1 · edited May 27 '20 at 07:52

31

don't reinvent the wheel, Boost String Algorithms is a header only library and I'm reasonably certain that it works everywhere. If you think the accepted answer code is better because its been provided and you don't need to look in docs, here.

#include <boost/algorithm/string.hpp>
#include <string>
#include <iostream>

int main()
{
    std::string str1 = "\r\nsomksdfkmsdf\r\nslkdmsldkslfdkm\r\n";
    boost::replace_all(str1, "\r\n", "Jane");
    std::cout<<str1;
}

edited May 27 '20 at 07:52

Noam M

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answered Jan 27 '09 at 20:00

Hippiehunter

967
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2

or just use standard library functions to avoid the boost dependency: http://stackoverflow.com/questions/1488775/c-remove-new-line-from-multiline-string – Code Abominator Aug 18 '14 at 03:07

score 16 · Accepted Answer · edited May 27 '20 at 07:26

16

Use this :

while ( str.find ("\r\n") != string::npos )
{
    str.erase ( str.find ("\r\n"), 2 );
}

more efficient form is :

string::size_type pos = 0; // Must initialize
while ( ( pos = str.find ("\r\n",pos) ) != string::npos )
{
    str.erase ( pos, 2 );
}

edited May 27 '20 at 07:26

Noam M

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41

answered Jan 27 '09 at 17:36

lsalamon

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1

Don't run the find twice! Store the position found in the conditional and use it in the body: while (size_type pos = str.find(...)) { str.manipulate(pos,...); }; – dmckee --- ex-moderator kitten Jan 27 '09 at 17:56
Hmmm...that still leaves something to be desired. Each iteration of the loop rescans the bit declared safe by the last pass. Define pos outside the loop and make it persistant: size_type pos = 0; while (pos = str.find("..",pos) )... – dmckee --- ex-moderator kitten Jan 27 '09 at 18:24
5

This is an erasure and not a replacement - the question asked was how to replace "\r\n"; they may have needed to replace it with another character. – SteJ Apr 03 '16 at 23:12