ABC HHHH fetID_3141 ProID_1045
The above is a string, I need to extract fetID_3141 and ProID_1045, mainly I need the numbers 3141 and 1045, how can I use C++ to do regular matching?
You can use std::regex for this.
#include <iostream>
#include <regex>
int main()
{
std::regex r("[a-zA-Z]+_([0-9]+)");
std::smatch m;
std::string s = "ABC HHHH fetID_3141 ProID_1045";
while (std::regex_search(s, m, r))
{
std::cout << m[1] << std::endl;
s = m.suffix().str();
}
}
Related
I have created this c++ to extract digits from mixed strings limited by xxx and yyy
Here is my code
#include <iostream>
#include <regex>
using namespace std;
int main() {
string text = "xxx1111yyy xxxrandomstring2222yyy";
string start_delimiter = "xxx";
string end_delimiter = "yyy";
regex pattern(start_delimiter + "([0-9]+)" + end_delimiter);
smatch match;
while (regex_search(text, match, pattern)) {
cout << match[1] << endl;
text = match.suffix().str();
}
return 0;
}
I expect the output:
1111
2222
But I'm getting in output only: 1111
Where is my fault ?
As I understand, delimiters xxx and yyyy are statics, randomstring isn't static so it can be any random string.
So the error simply is in your regex pattern.
it should something like this:
regex pattern("xxx.*?(\\d+).*?yyy");
The whole code could be like this:
#include <iostream>
#include <regex>
#include <string>
int main() {
std::string text =
"xxxrandomstring2222yyy xxx1111yyy";
std::regex pattern("xxx.*?(\\d+).*?yyy");
std::smatch match;
while (regex_search(text, match, pattern)) {
std::cout << match[1] << std::endl;
text = match.suffix().str();
}
return 0;
}
It is supposed to match "abababab" since "ab" is repeated more than two times consecutively but the code isn't printing any output.
Is there some other trick in using regex in C++.
I tried with other languages and it works just fine.
#include<bits/stdc++.h>
int main(){
std::string s ("xaxababababaxax");
std::smatch m;
std::regex e ("(.+)\1\1+");
while (std::regex_search (s,m,e)) {
for (auto x:m) std::cout << x << " ";
std::cout << std::endl;
s = m.suffix().str();
}
return 0;
}
Your problem is your backslashes are escaping the '1''s in your string. You need to inform std::regex to treat them as '\' 's. You can do this by using a raw string R"((.+)\1\1+)", or by escaping the slashes, as shown here:
#include <regex>
#include <string>
#include <iostream>
int main(){
std::string s ("xaxababababaxax");
std::smatch m;
std::regex e ("(.+)\\1\\1+");
while (std::regex_search (s,m,e)) {
for (auto x:m) std::cout << x << " ";
std::cout << std::endl;
s = m.suffix().str();
}
return 0;
}
Which produces the output
abababab ab
I need to get sentences with regex from String with word "walk". Now I am trying just to get sentences
std::string s ("Hello world! My name is Mike. Why so serious?");
std::smatch m;
std::regex e ("^\\s+[A-Za-z,;'\"\\s]+[.?!]$"); // matches words beginning by "sub"
while (std::regex_search (s,m,e)) {
for (auto w:m)
std::cout << w << "\n" ;
}
And this doesn't work.
Apart from start and end of the string in regex, you are forgetting to update the 's' with the suffix.
#include <iostream>
#include <regex>
int main()
{
std::string s ("Hello world! My name is Mike. Why so serious?");
std::smatch m;
std::regex e ("\\s?[A-Za-z,;'\"\\s]+[.?!]");
while(std::regex_search (s,m,e))
{
std::cout << m.str() << "\n" ;
s = m.suffix();
}
return 0;
}
What regex expression should I use to search all occurrences that match:
Start with 55 or 66
followed by a minimum 8 characters in the range of [0-9a-fA-F] (HEX numbers)
Ends with \r (a carriage return)
Example string: 0205065509085503400066/r09\r
My expected result:
5509085503400066\r
5503400066\r
My current result:
5509085503400066\r
Using
(?:55|66)[0-9a-fA-F]{8,}\r
As you can sie, this finds onlny the first result but not the second one.
Edit clarification
I search the string using Regex. It'll select the message for further parsing. The target string can start anywhere in the string. The target string is only valid if it only contains base-16 (HEX) numbers, and ends with a carriage return.
[start] [information part minimum 8 chars] [end symbol-carigge return]
I'm using the std::regex library in c++11 with the flag ECMAScript
Edit
I have created an alternative solution that gives me the expected result. But this is not pure regex.
#include <iostream>
#include <string>
#include <regex>
int main()
{
// repeated search (see also
std::regex_iterator)
std::string log("0055\r0655036608090705\r");
std::regex r("(?:55|66)[0-9a-fA-F]{8,}\r");
std::smatch sm;
while(regex_search(log, sm, r))
{
std::cout << sm.str() << '\n';
log = sm.str();
log += sm.suffix();
log[0] = 'a' ;
}
}
** Edit: Working regex solution based on comments **
#include <iostream>
#include <string>
#include <regex>
int main()
{
// repeated search (see also
std::regex_iterator)
std::string s("0055\r06550003665508090705\r0970");
std::regex r("(?=((?:55|66)[0-9a-fA-F]{8,}\r))");
auto words_begin =
std::sregex_iterator(s.begin(), s.end(), r);
auto words_end = std::sregex_iterator();
std::cout << "Found "
<< std::distance(words_begin, words_end)
<< " words:\n";
for (std::sregex_iterator i = words_begin; i != words_end; ++i) {
std::smatch match = *i;
std::string match_str = s.substr(match.position(1), match.length(1) - 1); //-1 cr
std::cout << match_str << " =" << match.position(1) << '\n';
}
}
Your are actually looking for overlapping matches. This can be achieved using a regex lookahead like this:
(?=((?:55|66)[0-9a-fA-F]{8,}\/r))
You will find the matches in question in group 1. The full-match, however, is empty.
Regex Demo (using /r instead of a carriage return for demonstration purposes only)
Sample Code:
#include <iostream>
#include <string>
#include <regex>
using namespace std;
int main() {
std::string subject("0055\r06550003665508090705\r0970");
try {
std::regex re("(?=((?:55|66)[0-9a-fA-F]{8,}\r))");
std::sregex_iterator next(subject.begin(), subject.end(), re);
std::sregex_iterator end;
while (next != end) {
std::smatch match = *next;
std::cout << match.str(1) << "\n";
next++;
}
} catch (std::regex_error& e) {
// Syntax error in the regular expression
}
return 0;
}
See also: Regex-Info: C++ Regular Expressions with std::regex
Using std::regex I want to create a function that takes, for example, a string
and creates a RegEx using that string, but with every char of the string matched literally.
For example, lets say s("[ds-aa]"); I want to create a RegEx using that string but literally so that the RegEx will match "\[ds\-aa\]".
Assuming you are using std::regex, and the default ECMA regex flavor, you just need to escape
. * + ? ^ $ { } ( ) | [ ] \
So, you can use
#include <regex>
#include <string>
#include <iostream>
using namespace std;
std::string regexEscape(std::string str) {
return std::regex_replace(str, std::regex(R"([.^$|()[\]{}*+?\\])"), R"(\$&)");
}
int main()
{
std::cout << "Test escaped pattern: " << regexEscape("[da-d$\\]") << std::endl; // = > \[da-d\$\\\]
std::string key = "\\56";
string input = "John\\56 Fred\\12";
std::regex rx(R"((\w+))" + regexEscape(key));
smatch m;
if (std::regex_search(input, m, rx)) {
std::cout << "Who has \\56? - " << m[1].str() << std::endl;
}
}
See IDEONE demo
Results:
Test escaped pattern: \[da-d\$\\\]
Who has \56? - John