How to get all matches from a string using regex?
I have a string:
".+(.cpp$|.cxx$|.d$|.h$|.hpp$)"
and I would like to get only the cpp cxx d h and hpp parts.
EDIT:
So basically I would like to construct regex which would match any string of characters starting with dot and ending with $.
I've tried the pattern: "\\.[^$+]+" which is supposed to match dot and everything else except $ and plus one or more times but this gets just the first .cpp part and I need all of them
Since you mention Qt in your question, here is how you would do it using QRegExp:
#include <QtCore>
#include <QtDebug>
int main(int argc, char **argv) {
QCoreApplication app(argc, argv);
QString target(".+(.cpp$|.cxx$|.d$|.h$|.hpp$)");
QRegExp pattern("\\.(\\w+)\\$");
QStringList matches;
int pos = 0;
while ((pos = pattern.indexIn(target, pos)) != -1) {
matches << pattern.cap(1);
pos += pattern.matchedLength();
}
qDebug() << matches; // "cpp", "cxx", "d", "h", "hpp"
return app.exec();
}
There's no generic solution as it really depends on how your regex implementation works and how it can be called - and considering there's no standard one for C++ (yet), you should mention which one you're using.
First of all you have to escape ., if it's meant to match a . and not just "any character". Also, I'd change the regex: "\.(d|[ch](?:pp|xx)?)$". This way you keep the dot as well as the line ending outside your match.
For the actual call (which will depend on your implementation) you'll have to use some kind of MATCH_ALL or GLOBAL_MATCH flag or simply loop over your input string, always starting after the previous match. Considering the line ending, you might simply use it once per input line (as I don't know your input data).
Find the location of the last "." and test the remaining string against all the suffixes you're interested in.
Since you are only interested in the elements between the punctuation marks, you can use them as separator to split the string with QStringList::split:
QString target = ".+(.cpp$|.cxx$|.d$|.h$|.hpp$)";
QStringList extensions = target.split(QRegExp("\\W+"), QString::SkipEmptyParts);
qDebug() << extensions; // ("cpp", "cxx", "d", "h", "hpp")
Related
So, I would like to change all words in a string except one, that stays in the middle.
#include <boost/algorithm/string/replace.hpp>
int main()
{
string test = "You want to join player group";
string find = "You want to join group";
string replace = "This is a test about group";
boost::replace_all(test, find, replace);
cout << test << endl;
}
The output was expected to be:
This is a test about player group
But it doesn't work, the output is:
You want to join player group
The problem is on finding out the words, since they are a unique string.
There's a function that reads all words, no matter their position and just change what I want?
EDIT2:
This is the best example of what I want to happen:
char* a = "This is MYYYYYYYYY line in the void Translate"; // This is the main line
char* b = "This is line in the void Translate"; // This is what needs to be find in the main line
char* c = "Testing - is line twatawtn thdwae voiwd Transwlate"; // This needs to replace ALL the words in the char* b, perserving the MYYYYYYYYY
// The output is expected to be:
Testing - is MYYYYYYYY is line twatawtn thdwae voiwd Transwlate
You need to invert your thinking here. Instead of matching "All words but one", you need to try to match that one word so you can extract it and insert it elsewhere.
We can do this with Regular Expressions, which became standardized in C++11:
std::string test = "You want to join player group";
static const std::regex find{R"(You want to join (\S+) group)"};
std::smatch search_result;
if (!std::regex_search(test, search_result, find))
{
std::cerr << "Could not match the string\n";
exit(1);
}
else
{
std::string found_group_name = search_result[1];
auto replace = boost::format("This is a test about %1% group") % found_group_name;
std::cout << replace;
}
Live Demo
To match the word "player" I used a pretty simply regular expression (\S+) which means "match one or more non-whitespace characters (greedily) and put that into a group"
"Groups" in regular expressions are enclosed by parentheses. The 0th group is always the entire match, and since we only have one set of parentheses, your word is therefore in group 1, hence the resulting access of the match result at search_result[1].
To create the regular expression, you'll notice I used the perhaps-unfamiliar string literal syntaxR"(...)". This is called a raw string literal and was also standardized in C++11. It was basically made for describing regular expressions without needing to escape backslashes. If you've used Python, it's the same as r'...'. If you've used C#, it's the same as #"..."
I threw in some boost::format to print the result because you were using Boost in the question and I thought you'd like to have some fun with it :-)
In your example, find is not a substring of test, so boost::replace_all(test, find, replace); has no effect.
Removing group from find and replace solves it:
#include <boost/algorithm/string/replace.hpp>
#include <iostream>
int main()
{
std::string test = "You want to join player group";
std::string find = "You want to join";
std::string replace = "This is a test about";
boost::replace_all(test, find, replace);
std::cout << test << std::endl;
}
Output: This is a test about player group.
In this case, there is just one replace of the beginning of the string because the end of the string is already the right one. You could have another call of replace_all to change the end if needed.
Some other options:
one is in the other answer.
split the strings into a vector (or array) of words, then insert the desired word (player) at the right spot of the replace vector, then build your output string from it.
I use a various regexes to parse a C source file, line by line. First i read all the content of file in a string:
ifstream file_stream("commented.cpp",ifstream::binary);
std::string txt((std::istreambuf_iterator<char>(file_stream)),
std::istreambuf_iterator<char>());
Then i use a set of regex, which should be applied continusly until the match found, here i will give only one for example:
vector<regex> rules = { regex("^//[^\n]*$") };
char * search =(char*)txt.c_str();
int position = 0, length = 0;
for (int i = 0; i < rules.size(); i++) {
cmatch match;
if (regex_search(search + position, match, rules[i],regex_constants::match_not_bol | regex_constants::match_not_eol))
{
position += ( match.position() + match.length() );
}
}
But it don't work. It will match the comment not in the current line, but it will search whole string, for the first match, regex_constants::match_not_bol and regex_constants::match_not_eol should make the regex_search to recognize ^$ as start/end of line only, not end start/end of whole block. So here is my file:
commented.cpp:
#include <stdio.h>
//comment
The code should fail, my logic is with those options to regex_search, the match should fail, because it should search for pattern in the first line:
#include <stdio.h>
But instead it searches whole string, and immideatly finds //comment. I need help, to make regex_search match only in current line. The options match_not_bol and match_not_eol do not help me. Of course i can read a file line by line in a vector, and then do match of all rules on each string in vector, but it is very slow, i have done that, and it take too long time to parse a big file like that, that's why i want to let regex deal with new lines, and use positioning counter.
If it is not what you want please comment so I will delete the answer
What you are doing is not a correct way of using a regex library.
Thus here is my suggestion for anyone that wants to use std::regex library.
It only supports ECMAScript that somehow is a little
poor than all modern regex library.
It has bugs as many as you like ( just I found ):
the same regex but different results on Linux and Windows only C++
std::regex and ignoring flags
std::regex_match and lazy quantifier with strange behavior
In some cases (I test specifically with std::match_results ) It is 200 times slower in comparison to std.regex in d language
It has very confusing flag-match and almost it does not work (at least for me)
conclusion: do not use it at all.
But if anyone still demands to use c++ anyway then you can:
use boost::regex about Boost library because:
It is PCRE support
It has less bug ( I have not seen any )
It is smaller in bin file ( I mean executable file after compiling )
It is faster then std::regex
use gcc version 7.1.0 and NOT below. The last bug I found is in version 6.3.0
use clang version 3 or above
If you have enticed (= persuade) to NOT use c++ then you can use:
Use d regular expression link library for large task: std.regex and why:
Fast Faster Command Line Tools in D
Easy
Flexible drn
Use native pcre or pcre2 link that have been written in c
Extremely fast but a little complicated
Use perl for a simple task and specially Perl one-liner link
#include <stdio.h>
//comment
The code should fail, my logic is with those options to regex_search, the match should fail, because it should search for pattern in the first line:
#include <stdio.h>
But instead it searches whole string, and immideatly finds //comment. I need help, to make regex_search match only in current line.
Are you trying to match all // comments in a source code file, or only the first line?
The former can be done like this:
#include <iostream>
#include <fstream>
#include <regex>
int main()
{
auto input = std::ifstream{"stream_union.h"};
for(auto line = std::string{}; getline(input, line); )
{
auto submatch = std::smatch{};
auto pattern = std::regex(R"(//)");
std::regex_search(line, submatch, pattern);
auto match = submatch.str(0);
if(match.empty()) continue;
std::cout << line << std::endl;
}
std::cout << std::endl;
return EXIT_SUCCESS;
}
And the later can be done like this:
#include <iostream>
#include <fstream>
#include <regex>
int main()
{
auto input = std::ifstream{"stream_union.h"};
auto line = std::string{};
getline(input, line);
auto submatch = std::smatch{};
auto pattern = std::regex(R"(//)");
std::regex_search(line, submatch, pattern);
auto match = submatch.str(0);
if(match.empty()) { return EXIT_FAILURE; }
std::cout << line << std::endl;
return EXIT_SUCCESS;
}
If for any reason you're trying to get the position of the match, tellg() will do that for you.
I'm writing a program that use QRegularExpression and MultilineOption, I wrote this code but matching stop on first line. Why? Where am I doing wrong?
QString recv = "AUTH-<username>-<password>\nINFO-ID:45\nREG-<username>-<password>-<name>-<status>\nSEND-ID:195-DATE:12:30 2/02/2015 <esempio>\nUPDATEN-<newname>\nUPDATES-<newstatus>\n";
QRegularExpression exp = QRegularExpression("(SEND)-ID:(\\d{1,4})-DATE:(\\d{1,2}):(\\d) (\\d{1,2})\/(\\d)\/(\\d{2,4}) <(.+)>\\n|(AUTH)-<(.+)>-<(.+)>\\n|(INFO)-ID:(\\d{1,4})\\n|(REG)-<(.+)>-<(.+)>-<(.+)>-<(.+)>\\n|(UPDATEN)-<(.+)>\\n|(UPDATES)-<(.+)>\\n", QRegularExpression::MultilineOption);
qDebug() << exp.pattern();
QRegularExpressionMatch match = exp.match(recv);
qDebug() << match.lastCapturedIndex();
for (int i = 0; i <= match.lastCapturedIndex(); ++i) {
qDebug() << match.captured(i);
}
Can someone help me?
The answer is you should use .globalMatch method rather than .match.
See QRegularExpression documentation on that:
Attempts to perform a global match of the regular expression against
the given subject string, starting at the position offset inside the
subject, using a match of type matchType and honoring the given
matchOptions. The returned QRegularExpressionMatchIterator is
positioned before the first match result (if any).
Also, you can remove the QRegularExpression::MultilineOption option as it is not being used.
Sample code:
QRegularExpressionMatchIterator i = exp.globalMatch(recv);
while (i.hasNext()) {
QRegularExpressionMatch match = i.next();
// ...
}
Actually I google'd this question having similar issue, but I couldn't agree completely with an answer, as I think most of the questions about multi-line matching with new QRegularExpression can be answered as following:
use QRegularExpression::DotMatchesEverythingOption option which allows (.) to match newline characters. Which is extremely useful then porting from QRegExp
you got an or Expression and the first one is true, job is done.
you need to split the string and loop the array to compare with this Expression will work i think.
If the data every times have the same struct you can use something like this:
"(AUTH)-<([^>]+?)>-<([^>]+?)>\\nINFO-ID:(\\d+)\\n(REG)-<([^>]+?)>-<([^>]+?)>-<([^>]+?)>-<([^>]+?)>\\n(SEND)-ID:(\\d+)-DATE:(\\d+):(\\d+) (\\d+)/(\\d+)/(\\d+) <([^>]+?)>\\n(UPDATEN)-<([^>]+?)>\\n(UPDATES)-<([^>]+?)>"
21 Matches
for those asking, the {0} allows selection of any one block within the sResult string separated by the | 0 is the first block
it needs to be dynamic for future expansion as that number will be configurable by users
So I am working on a regex to extract 1 portion of a string, however while it matches the results return are not what is expected.
std::string sResult = "MATCH_ME|BUT|NOT|ANYTHNG|ELSE";
std::regex pattern("^(?:[^|]+[|]){0}([^|;]+)");
std::smatch regMatch;
std::regex_search(sResult, regMatch, pattern);
if(regMatch[1].matched)
{
for( int i = 0; i < regMatch.size(); i++)
{
//SUBMATCH 0 = "MATCH_ME|BUT|NOT|ANYTHNG|ELSE"
//SUBMATCH 1 = "BUT|NOT|ANYTHNG|ELSE"
std::ssub_match sm = regMatch[i];
bValid = strcmp(regMatch[i].str().c_str(), pzPoint->_ptrTarget->_pzTag->szOPCItem);
}
}
For some reason I cannot figure out the code to get me just the MATCH_ME back so I can compare it to expected results list on the C++ side.
Anyone have any ideas on where I went wrong here.
It seems you're using regular expressions for what they haven't been designed for. You should first split your string at the delimiter | and apply regular expressions on the resulting tokens if you want to check them for validity.
By the way: The std::regex implementation in libstdc++ seems to be buggy. I just did some tests and found that even simple patterns containing escaped pipe characters like \\| failed to compile throwing a std::regex_error with no further information in the error message (GCC 4.8.1).
The following code example shows how to do what you are after - you compile this, then call it with a single numerical argument to extract that element of the input:
#include <iostream>
#include <cstring>
#include <regex>
int main(int argc, char *argv[]) {
char pat[100];
if (argc > 1) {
sprintf(pat, "^(?:[^|]+[|]){%s}([^|;]+)", argv[1]);
std::string sResult = "MATCH_ME|BUT|NOT|ANYTHNG|ELSE";
std::regex pattern(pat);
std::smatch regMatch;
std::regex_search(sResult, regMatch, pattern);
if(regMatch[1].matched)
{
std::ssub_match sm = regMatch[1];
std::cout << "The match is " << sm << std::endl;
//bValid = strcmp(regMatch[i].str().c_str(), pzPoint->_ptrTarget->_pzTag->szOPCItem);
}
}
return 0;
}
Creating an executable called match, you can then do
>> match 2
The match is NOT
which is what you wanted.
The regex, it turns out, works just fine - although as a matter of preference I would use \| instead of [|] for the first part.
Turns out the problem was on the C side in extracting the match, it had to be done more directly, below is the code that gets me exactly what I wanted out of the string so I can use it later.
std::string sResult = "MATCH_ME|BUT|NOT|ANYTHNG|ELSE";
std::regex pattern("^(?:[^|]+[|]){0}([^|;]+)");
std::smatch regMatch;
std::regex_search(sResult, regMatch, pattern);
if(regMatch[1].matched)
{
std::string theMatchedPortion = regMatch[1];
//the issue was not with the regex but in how I was retrieving the results.
//theMatchedPortion now equals "MATCH_ME" and by changing the number associated
with it I can navigate through the string
}
I have a regex which I hope means any file with extension listed:
((\\.cpp$)|(\\.cxx$)|(\\.c$)|(\\.hpp$)|(\\.h$))
How to compare it in Qt against selected file?
Your actual RegEx itself doesn't have double backslashes (just when you fit it into a string literal). And you'll need some kind of wildcard if you want to use it to match full filenames. There's a semantic issue of whether you want a file called just ".cpp" to match or not. What about case sensitivity?
I'll assume for the moment that you want at least one other character in the beginning and use .+:
.+((\.cpp$)|(\.cxx$)|(\.c$)|(\.hpp$)|(\.h$))
So this should work:
QRegExp rx (".+((\\.cpp$)|(\\.cxx$)|(\\.c$)|(\\.hpp$)|(\\.h$))");
bool isMatch = rx.exactMatch(filename);
But with the expressive power of a whole C++ compiler at your beck and call, it can be a bit stifling to use regular expressions. You might have an easier time adapting code if you write it more like:
bool isMatch = false;
QStringList fileExtensionList;
fileExtensionList << "CPP" << "CXX" << "C" << "HPP" << "H";
QStringList splitFilenameList = filename.split(".");
if(splitFilenameList.size() > 1) {
QString fileExtension = splitFilenameList[splitFilenameList.size() - 1];
isMatch = fileExtensionList.contains(fileExtension.toUpper()));
}