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Std::regex_iterator function in C++

In this article, you will learn about the std::regex_iterator in C++ with its syntax and examples.

What is the std::regex_iterator?

A C++ Standard Library class called std::regex_iterator represents an iterator for paging over a string sequence that matches a regular expression. It is a component of the regular expression support added to the C++ Standard Library in C++11. Use the std::regex_iterator function to locate and iterate over matches of a common expression pattern within a given input text.


Let us take an example to demonstrate the usage of std::regex_iterator in C++:


Std::regex_iterator function in C++


  • Using std::regex function, we build a regular expression pattern to match one or more digits (\\d+).
  • We construct a std::regex_iterator to iterate over matches in the text string. It requires the regular expression pattern and the text's start and end iterators.
  • A while loop is used to iterate over the matches, and iter->str() is used to output each match. The iterator is incremented to go to the following match.
  • The std::regex_iterator is a helpful tool for information extraction and parsing from strings that fit a specific pattern. It can be used in situations like extracting numbers, email addresses, or other structured data, where you must locate and handle every instance of a regular expression in the text. It offers an easy and standardized approach to iterate over matches, which streamlines the work with regular expressions in C++.

Benefits of Std::regex_iterator function

In C++, std::regex_iterator provides several advantages for text processing and regular expression operations. The following are some benefits of using std::regex_iterator:

Text Pattern Matching: std::regex_iterator makes pattern matching in text easier. Creating a regular expression pattern is simple, and you can use the iterator to locate every instance of the pattern in the input text.

Flexibility: It offers you a choice of different actions when it comes to iterating over matches, including finding all matches, finding the first match, and iterating with custom increments.

Iteration: It eliminates the need for complicated loop structures and manual string index management by allowing you to iterate over several matches in a text. It makes it easier to parse structured data from text.

Standard Library Integration: It is widely accessible and consistent across many platforms and C++ compilers because it is a component of the C++ Standard Library. Working with regular expressions in C++ does not require external libraries.

Type Safety: It guarantees that you are using the right types for matches, iterators, and pattern matching while working with regular expressions.

Robustness: std::regex_iterator is a robust tool for text parsing because it is made to handle several edge situations and corner circumstances connected to regular expression matching.

Upgraded Readability: It can result in more readable and maintainable code that is easier to understand by abstracting away many of the low-level intricacies associated with regex matching.

Compatibility: Integrating std::regex_iterator into existing C++ programs is made easier by its compatibility with other C++ Standard Library parts and data structures.

API standardization: For C++ developers, the standardization of std::regex_iterator makes regex operations easier to understand and apply by offering a standardized and well-defined API.

Performance: It is a performant alternative for regex matching in C++ programs since it is optimized for efficiency.


Std::regex_iterator is an effective and practical utility for working with regular expressions in C++ overall. It facilitates locating and analyzing textual matches, making working with textual and structured data in your C++ applications easier.

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