Answer by Toby Speight for How do I check if a C++ std::string starts with a...
From C++23 onwards, you can use std::ranges::starts_with(), which works on any sequence type, including std::string and std::string_view, in any combination:#include <algorithm>#include...
View ArticleAnswer by TarmoPikaro for How do I check if a C++ std::string starts with a...
C++20, use s.starts_with(), see link for examples:https://en.cppreference.com/w/cpp/string/basic_string/starts_with
View ArticleAnswer by Guss for How do I check if a C++ std::string starts with a certain...
C++20 update :Use std::string::starts_withhttps://en.cppreference.com/w/cpp/string/basic_string/starts_withstd::string str_value = /* smthg */;const auto starts_with_foo =...
View ArticleAnswer by CM777 for How do I check if a C++ std::string starts with a certain...
In C++20 now there is starts_with available as a member function of std::string defined as:constexpr bool starts_with(string_view sv) const noexcept;constexpr bool starts_with(CharT c) const...
View ArticleAnswer by Sam Kumar for How do I check if a C++ std::string starts with a...
Starting with C++20, you can use the starts_with method.std::string s = "abcd";if (s.starts_with("abc")) { ...}
View ArticleAnswer by Melroy van den Berg for How do I check if a C++ std::string starts...
With C++11 or higher you can use find() and find_first_of()Example using find to find a single char:#include <string>std::string name = "Aaah";size_t found_index = name.find('a');if (found_index...
View ArticleAnswer by Parker for How do I check if a C++ std::string starts with a...
In case you need C++11 compatibility and cannot use boost, here is a boost-compatible drop-in with an example of usage:#include <iostream>#include <string>static bool starts_with(const...
View ArticleAnswer by alextoind for How do I check if a C++ std::string starts with a...
Since C++11 std::regex_search can also be used to provide even more complex expressions matching. The following example handles also floating numbers thorugh std::stof and a subsequent cast to...
View ArticleAnswer by Roi Danton for How do I check if a C++ std::string starts with a...
With C++17 you can use std::basic_string_view& with C++20 std::basic_string::starts_with or std::basic_string_view::starts_with. The benefit of std::string_view in comparison to std::string -...
View ArticleAnswer by Macsinus for How do I check if a C++ std::string starts with a...
text.substr(0, start.length()) == start
View ArticleAnswer by Shital Shah for How do I check if a C++ std::string starts with a...
I use std::string::compare wrapped in utility method like below:static bool startsWith(const string& s, const string& prefix) { return s.size() >= prefix.size() && s.compare(0,...
View ArticleAnswer by mois for How do I check if a C++ std::string starts with a certain...
std::string text = "--foo=98";std::string start = "--foo=";if (text.find(start) == 0){ int n = stoi(text.substr(start.length())); std::cout << n << std::endl;}
View ArticleAnswer by Ludovic Aubert for How do I check if a C++ std::string starts with...
Use rfind overload that takes the search position pos parameter, and pass zero for it:std::string s = "tititoto";if (s.rfind("titi", 0) == 0) { // pos=0 limits the search to the prefix // s starts with...
View ArticleAnswer by Marcelo Cantos for How do I check if a C++ std::string starts with...
Given that both strings —argv[1] and "--foo"— are C strings, @FelixDombek's answer is hands-down the best solution.Seeing the other answers, however, I thought it worth noting that, if your text is...
View ArticleAnswer by Carl Cook for How do I check if a C++ std::string starts with a...
Why not use gnu getopts? Here's a basic example (without safety checks):#include <getopt.h>#include <stdio.h>int main(int argc, char** argv){ option long_options[] = { {"foo",...
View ArticleAnswer by matiu for How do I check if a C++ std::string starts with a certain...
Nobody used the STL algorithm/mismatch function yet. If this returns true, prefix is a prefix of 'toCheck':std::mismatch(prefix.begin(), prefix.end(), toCheck.begin()).first == prefix.end()Full example...
View ArticleAnswer by szx for How do I check if a C++ std::string starts with a certain...
You can also use strstr:if (strstr(str, substr) == substr) { // 'str' starts with 'substr'}but I think it's good only for short strings because it has to loop through the whole string when the string...
View ArticleAnswer by Huseyin Yagli for How do I check if a C++ std::string starts with a...
Code I use myself:std::string prefix = "-param=";std::string argument = argv[1];if(argument.substr(0, prefix.size()) == prefix) { std::string argumentValue = argument.substr(prefix.size());}
View ArticleAnswer by razvanco13 for How do I check if a C++ std::string starts with a...
Using STL this could look like:std::string prefix = "--foo=";std::string arg = argv[1];if (prefix.size()<=arg.size() && std::equal(prefix.begin(), prefix.end(), arg.begin())) {...
View ArticleAnswer by Felix Dombek for How do I check if a C++ std::string starts with a...
Just for completeness, I will mention the C way to do it:If str is your original string, substr is the substring you want to check, then strncmp(str, substr, strlen(substr))will return 0 if str starts...
View ArticleAnswer by Nils for How do I check if a C++ std::string starts with a certain...
Ok why the complicated use of libraries and stuff? C++ String objects overload the [] operator, so you can just compare chars.. Like what I just did, because I want to list all files in a directory and...
View ArticleAnswer by Tom for How do I check if a C++ std::string starts with a certain...
At the risk of being flamed for using C constructs, I do think this sscanf example is more elegant than most Boost solutions. And you don't have to worry about linkage if you're running anywhere that...
View ArticleAnswer by blwy10 for How do I check if a C++ std::string starts with a...
if(boost::starts_with(string_to_search, string_to_look_for)) intval = boost::lexical_cast<int>(string_to_search.substr(string_to_look_for.length()));This is completely untested. The principle is...
View ArticleAnswer by Thomas for How do I check if a C++ std::string starts with a...
You would do it like this:std::string prefix("--foo=");if (!arg.compare(0, prefix.size(), prefix)) foo_value = std::stoi(arg.substr(prefix.size()));Looking for a lib such as Boost.ProgramOptions that...
View ArticleAnswer by Ferruccio for How do I check if a C++ std::string starts with a...
If you're already using Boost, you can do it with boost string algorithms+boost lexical cast:#include <boost/algorithm/string/predicate.hpp>#include <boost/lexical_cast.hpp>try { if...
View ArticleHow do I check if a C++ std::string starts with a certain string, and convert...
How do I implement the following (Python pseudocode) in C++?if argv[1].startswith('--foo='): foo_value = int(argv[1][len('--foo='):])(For example, if argv[1] is --foo=98, then foo_value is 98.)Update:...
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