Regex doesn't match in c but works with online interpreter - c

Question

I have a regex that I have tested with https://regexr.com/, where it works correctly. But in c it doesn't find any match.
My code is below; I have removed everything unnecessary.
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <regex.h>
int main ()
{
char * str = "<sql db=../serverTcp/Testing.db query=SELECT * From BuyMarsians;\>";
char * regex = "<sql\s+db=(.+)\s+query=(.+;)\s*\\>";
regex_t regexCompiled;
if (regcomp(&regexCompiled,regex,REG_EXTENDED))
{
printf("Could not compile regular expression.\n");
fflush(stdout);
};
if (!regexec(&regexCompiled,str, 0, NULL, 0)) {
printf("matched");
fflush(stdout);
}
regfree(&regexCompiled);
return 0;
}

Answer 1

You need to escape your backslashes. Change
char * regex = "<sql\s+db=(.+)\s+query=(.+;)\s*\\>";
to
char * regex = "<sql\\s+db=(.+)\\s+query=(.+;)\\s*\\\\>";
Note that this is extremely inefficient. A much more efficient regex uses non-greedy quantification, with ?:
<sql\s+db=(.+?)\s+query=(.+;)\s*\\>
// ^ key change
That becomes:
char * regex = "<sql\\s+db=(.+?)\\s+query=(.+;)\\s*\\\\>";
Also note: Your string to be matched also includes \. You need to escape it there, too:
char * str = "<sql db=../serverTcp/Testing.db query=SELECT * From BuyMarsians;\\>";
Here's a working demo of your corrected code.