I have this code:
std::smatch m;
std::string dataType = "type = struct A {\nint a;\nint b;\nint c; }";
std::regex_search(dataType, m, std::regex("(= )(.*)( [{]|\n|$)"));
std::cout << m.str(2) << std::endl;
The problem is that it returns the longest match, but I need the smallest.
The output is:
struct A {\n
int a;\n
int b;\n
int c; }
But it needs to be:
struct A
How can I get the result I want?
You could change .* to .*?.
Read up on greediness.
(Did you really mean to put a literal newline in the regex? You probably want to make that \\n.)
To get "struct A" from your text, the regex to be used is:
\=\s(\w+\s\w+)
if you have other cases, please give more specifications or examples of your input and how your output should look like.
Edit:
thanks to user3259253, the correct solution is:
\\=\\s(\\w+(\\s\\w+)?)
Right, use this:
std::regex_search(dataType, m, std::regex("(= )(.*)([\\{]|\\n)$"));
However, if you only what to capture what's between the = sign and the curly bracket/end of line, you don't need so many () groups. This would be enough:
std::regex_search(dataType, m, std::regex("= (.*)[\\{]|\\n$"));
std::cout << m.str(1) << std::endl;
Note that here we're catching the text as the first entry, m.str(1), instead of the second, because we have eliminated "(= )"
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'm trying to recognise certain phrases within a user defined string but so far have only been able to get a single word.
For example, if I have the sentence:
"What do you think of stack overflow?"
is there a way to search for "What do you" within the string?
I know you can retrieve a single word with the find function but when attempting to get all three it gets stuck and can only search for the first.
Is there a way to search for the whole string in another string?
Use str.find()
size_t find (const string& str, size_t pos = 0)
Its return value is the starting position of the substring. You can test if the string you are looking for is contained in the main string by performing the simple boolean test of returning str::npos:
string str = "What do you think of stack overflow?";
if (str.find("What do you") != str::npos) // is contained
The second argument can be used to limit your search from certain string position.
The OP question mentions it gets stuck in the attempt to find a three word string. Actually, I believe you are misinterpreting the return value. It happens that the return for the single word search "What" and the string "What do you" have coincidental starting positions, therefore str.find() returns the same. To search for individual words positions, use multiple function calls.
Use regular expressions
#include <iostream>
#include <string>
#include <regex>
int main ()
{
std::string s ("What do you think of stack overflow?");
std::smatch m;
std::regex e ("\\bWhat do you think\\b");
std::cout << "The following matches and submatches were found:" << std::endl;
while (std::regex_search (s,m,e)) {
for (auto x:m) std::cout << x << " ";
std::cout << std::endl;
s = m.suffix().str();
}
return 0;
}
Also you can find wildcards implementing with boost (regex in std library was boost::regex library before c++11) there
I'm failing to create a pattern for the stl regex_match function and need some help understanding why the pattern I created doesn't work and what would fix it.
I think the regex would have a hit for dl.boxcloud.com but it does not.
****still looking for input. I updated the program reflect suggestions. There are two matches when I think should be one.
#include <string>
#include <regex>
using namespace std;
wstring GetBody();
int _tmain(int argc, _TCHAR* argv[])
{
wsmatch m;
wstring regex(L"(dl\\.boxcloud\\.com|api-content\\.dropbox\\.com)");
regex_search(GetBody(), m, wregex(regex));
printf("%d matches.\n", m.size());
return 0;
}
wstring GetBody() {
wstring body(L"ABOUTLinkedIn\r\n\r\nwall of textdl.boxcloud.com/this/file/bitbyte.zip sent you a message.\r\n\r\nDate: 12/04/2012\r\n\r\nSubject: RE: Reference Ask\r\n\r\nOn 12/03/12 2:02 PM, wall of text wrote:\r\n--------------------\r\nRuba,\r\n\r\nI am looking for a n.");
return body;
}
There is no problem with the code itself. You mistake m.size() for the number of matches, when in fact, it is a number of groups your regex returns.
The std::match_results::size reference is not helpful with understanding that:
Returns the number of matches and sub-matches in the match_results object.
There are 2 groups (since you defined a capturing group around the 2 alternatives) and 1 match all in all.
See this IDEONE demo
#include <regex>
#include <string>
#include <iostream>
#include <time.h>
using namespace std;
int main()
{
string data("ABOUTLinkedIn\r\n\r\nwall of textdl.boxcloud.com/this/file/bitbyte.zip sent you a message.\r\n\r\nDate: 12/04/2012\r\n\r\nSubject: RE: Reference Ask\r\n\r\nOn 12/03/12 2:02 PM, wall of text wrote:\r\n--------------------\r\nRuba,\r\n\r\nI am looking for a n.");
std::regex pattern("(dl\\.boxcloud\\.com|api-content\\.dropbox\\.com)");
std::smatch result;
while (regex_search(data, result, pattern)) {
std::cout << "Match: " << result[0] << std::endl;
std::cout << "Captured text 1: " << result[1] << std::endl;
std::cout << "Size: " << result.size() << std::endl;
data = result.suffix().str();
}
}
It outputs:
Match: dl.boxcloud.com
Captured text 1: dl.boxcloud.com
Size: 2
See, the captured text equals the whole match.
To "fix" that, you may use non-capturing group, or remove grouping at all:
std::regex pattern("(?:dl\\.boxcloud\\.com|api-content\\.dropbox\\.com)");
// or
std::regex pattern("dl\\.boxcloud\\.com|api-content\\.dropbox\\.com");
Also, consider using raw string literal when declaring a regex (to avoid backslash hell):
std::regex pattern(R"(dl\.boxcloud\.com|api-content\.dropbox\.com)");
You need to add another "\" before each ".". I think that should fix it. You need to use escape character to represent "\" so your regex looks like this
wstring regex(L"(dl\\.boxcloud\\.com|api-content\\.dropbox\\.com)");
Update:
As #user3494744 also said you have to use
std::regex_search
instead of
std::regex_match.
I tested and it works now.
The problem is that you use regex_match instead of regex_search. To quote from the manual:
Note that regex_match will only successfully match a regular expression to an entire character sequence, whereas std::regex_search will successfully match subsequences
This fix will give a match, but too many since you also have to replace \. by \\. as shown before my answer. Otherwise the string "dlXboxcloud.com" will also match.
Say I have strings like these:
bunch of other html<a href="http://domain.com/133742/The_Token_I_Want.zip" more html and stuff
bunch of other html<a href="http://domain.com/12345/another_token.zip" more html and stuff
bunch of other html<a href="http://domain.com/0981723/YET_ANOTHER_TOKEN.zip" more html and stuff
What is the regular expression to match The_Token_I_Want, another_token, YET_ANOTHER_TOKEN?
Appendix B of RFC 2396 gives a doozy of a regular expression for splitting a URI into its components, and we can adapt it for your case
^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*/([^.]+)[^?#]*)(\?([^#]*))?(#(.*))?
#######
This leaves The_Token_I_Want in $6, which is the “hashderlined” subexpression above. (Note that the hashes are not part of the pattern.) See it live:
#! /usr/bin/perl
$_ = "http://domain.com/133742/The_Token_I_Want.zip";
if (m!^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*/([^.]+)[^?#]*)(\?([^#]*))?(#(.*))?!) {
print "$6\n";
}
else {
print "no match\n";
}
Output:
$ ./prog.pl
The_Token_I_Want
UPDATE: I see in a comment that you're using boost::regex, so remember to escape the backslash in your C++ program.
#include <boost/foreach.hpp>
#include <boost/regex.hpp>
#include <iostream>
#include <string>
int main()
{
boost::regex token("^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*"
"/([^.]+)"
// ####### I CAN HAZ HASHDERLINE PLZ
"[^?#]*)(\\?([^#]*))?(#(.*))?");
const char * const urls[] = {
"http://domain.com/133742/The_Token_I_Want.zip",
"http://domain.com/12345/another_token.zip",
"http://domain.com/0981723/YET_ANOTHER_TOKEN.zip",
};
BOOST_FOREACH(const char *url, urls) {
std::cout << url << ":\n";
std::string t;
boost::cmatch m;
if (boost::regex_match(url, m, token))
t = m[6];
else
t = "<no match>";
std::cout << " - " << m[6] << '\n';
}
return 0;
}
Output:
http://domain.com/133742/The_Token_I_Want.zip:
- The_Token_I_Want
http://domain.com/12345/another_token.zip:
- another_token
http://domain.com/0981723/YET_ANOTHER_TOKEN.zip:
- YET_ANOTHER_TOKEN
/a href="http://domain.com/[0-9]+/([a-zA-Z_]+).zip"/
Might want to add more characters to [a-zA-Z_]+
You can use:
(http|ftp)+://[[:alnum:]./_]+/([[:alnum:]._-]+).[[:alnum:]_-]+
([[:alnum:]._-]+) is a group for the matched pattern, and in your example its value will be The_Token_I_Want. to access this group, use \2 or $2, because (http|ftp) is the first group and ([[:alnum:]._-]+) is the second group of the matched pattern.
Try this:
/(?:f|ht)tps?:/{2}(?:www.)?domain[^/]+.([^/]+).([^/]+)/i
or
/\w{3,5}:/{2}(?:w{3}.)?domain[^/]+.([^/]+).([^/]+)/i
First, use an HTML parser and get a DOM. Then get the anchor elements and loop over them looking for the hrefs. Don't try to grab the token straight out of a string.
Then:
The glib answer would be:
/(The_Token_I_Want.zip)/
You might want to be a little more precise then a single example.
I'm guessing you are actually looking for:
/([^/]+)$/
m/The_Token_I_Want/
You'll have to be more specific about what kind of token it is. A number? A string? Does it repeat? Does it have a form or pattern to it?
It's probably best to use something smarter than a RegEx. For example, if you're using C# you could use the System.Uri class to parse it for you.
I have this simple piece of code in c++:
int main(void)
{
string text = "http://www.amazon.com";
string a,b,c,d,e,f;
pcrecpp::RE re("^((\\w+):\\/\\/\\/?)?((\\w+):?(\\w+)?#)?([^\\/\\?:]+):?(\\d+)?(\\/?[^\\?#;\\|]+)?([;\\|])?([^\\?#]+)?\\??([^#]+)?#?(\\w*)");
if(re.PartialMatch(text, &a,&b,&c,&d,&e,&f))
{
std::cout << "match: " << f << "\n";
// should print "www.amazon.com"
}else{
std::cout << "no match. \n";
}
return 0;
}
When I run this it doesn't find a match.
I pretty sure that the regex pattern is correct and my code is what's wrong.
If anyone familiar with pcrecpp can take a look at this Ill be grateful.
EDIT:
Thanks to Dingo, it works great.
another issue I had is that the result was at the sixth place - "f".
I edited the code above so you can copy/paste if you wish.
The problem is that your code contains ??( which is a trigraph in C++ for [. You'll either need to disable trigraphs or do something to break them up like:
pcrecpp::RE re("^((\\w+):\\/\\/\\/?)?((\\w+):?(\\w+)?#)?([^\\/\\?:]+):?(\\d+)?(\\/?[^\\?#;\\|]+)?([;\\|])?([^\\?#]+)?\\??" "([^#]+)?#?(\\w*)");
Please do
cout << re.pattern() << endl;
to double-check that all your double-slashing is done right (and also post the result).
Looks like
^((\w+):///?)?((\w+):?(\w+)?#)?([^/\?:]+):?(\d+)?(/?[^\?#;\|]+)?([;\|])?([^\?#]+)?\??([^#]+)?#?(\w*)
The hostname isn't going to be returned from the first capture group, why are you using parentheses around for example \w+ that you aren't wanting to capture?