Regex search for Text then match elements

Question

I would like to install a condition. I have already tried a lot but without success. Would someone be so kind and would help me?

My goal: if SharedKeys true then match elements(A B C D).

SharedKeys = "A","B","C","D"

Regex: (?!\")[A-Z]*?(?=\")

Match elements: A B C D

Update: (SharedKeys)?(?(1)|(?!\")[A-Z]*?(?=\"))

Match elements: SharedKeys A B C D

Link: https://regex101.com/r/WFxZh4/1

I think i have now what i needed, maybe helps others.

SharedKeys = "A","B","C","D"

BlaBla = "B", "B", "C"

Result: (SharedKeys|BlaBla)?(?(1)|(?!\")[A-Z]*?(?=\"))

Match elements: SharedKeys A B C D BlaBla B B C

Result for c++: [A-Za-z]+|(?!\")[A-Z]*?(?=\") (std::regex)

some times it's easier to match 'Sendkeys = ....' and then match elements inside the recent matched string, in two steps @Lendoria — MohaMad, Jul 04 '17 at 15:20
read [C++: what regex library should I use](https://stackoverflow.com/questions/181624/c-what-regex-library-should-i-use) and [Comparison of regular expression engines](https://en.wikipedia.org/wiki/Comparison_of_regular_expression_engines) — MohaMad, Jul 04 '17 at 16:07
`C++` does not support **if else** condition. So your pattern is fail. It support by default: `ECMAScript 262` — Shakiba Moshiri, Jul 04 '17 at 16:24
Instead of `std:::regex` that is buggy and poor, you can use: `boost::regex` — Shakiba Moshiri, Jul 04 '17 at 16:26

Shakiba Moshiri · Accepted Answer · 2017-07-04T16:52:24.697

with std::regex:

std::string s1( R"(SharedKeys = "A","B","C","D")" );
std::regex rx( "(SharedKeys)?(?(1)|[A-Z](?=\\\"))" );
std::match_results< std::string::const_iterator > mr;

while( std::regex_search( s1, mr, rx ) ){
    std::cout << mr.str() << '\n';
    s1 = mr.suffix().str();
}

the output:

terminate called after throwing an instance of 'std::regex_error'  
what():  Invalid special open parenthesis. Aborted (core dumped)

with boost::regex:

std::string s1( R"(SharedKeys = "A","B","C","D")" );
boost::regex rx( "(SharedKeys)?(?(1)|[A-Z](?=\\\"))" );
boost::match_results< std::string::const_iterator > mr;

while( boost::regex_search( s1, mr, rx ) ){
    std::cout << mr.str() << '\n';
    s1 = mr.suffix().str();
}

the output:

SharedKeys
A
B
C
D

here you can see the difference between this two flavors:

source of the screenshot

Note. The std::regex is buggy especially with gcc version 6.3.0 and lower versions

Thanks for your description! I use only std:regex so i have write another algorythm. In futur maybe i add Boost:regex. Thank you! — Lendoria, Jul 04 '17 at 16:53
@Lendoria. you are welcome. It is faster and richer and safer — Shakiba Moshiri, Jul 04 '17 at 16:54

Regex search for Text then match elements

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