Create regex from glob expression

Question

i write program that parse text with regular expression. Regular expression should be obtained from user. I deside to use glob syntax for user input, and convert glob string

Answer 1

I'm not sure I fully understand the requirements. If I assume the users want to find text "entries" where their search matches then I think this brute way would work as a start.

First escape everything regex-meaningful. Then use non-regex replaces for replacing the (now escaped) glob characters and build the regular expression. Like so in Python:

regexp = re.escape(search_string).replace(r'\?', '.').replace(r'\*', '.*?')

For the search string in the question, this builds a regexp that looks like so (raw):

foo\..\ bar.*?

Used in a Python snippet:

search = "foo.? bar*"
text1 = 'foo bar'
text2 = 'gazonk foo.c bar.m m.bar'

searcher = re.compile(re.escape(s).replace(r'\?', '.').replace(r'\*', '.*?'))

for text in (text1, text2):
  if searcher.search(text):
    print 'Match: "%s"' % text

Produces:

Match: "gazonk foo.c bar.m m.bar"

Note that if you examine the match object you can find out more about the match and use for highlighting or whatever.

Of course, there might be more to it, but it should be a start.

Answer 2

In R, there's the glob2rx function included in the base distribution:

http://stat.ethz.ch/R-manual/R-devel/library/utils/html/glob2rx.html

Answer 3

Jakarta ORO has an implementation in Java.

Answer 4

jPaq's RegExp.fromWildExp function does something similar to this. The following is taken from the example that is on the front page of the site:

// Find a first substring that starts with a capital "C" and ends with a
// lower case "n".
alert("Where in the world is Carmen Sandiego?".findPattern("C*n"));

// Finds two words (first name and last name), flips their order, and places
// a comma between them.
alert("Christopher West".replacePattern("(<*>) (<*>)", "p", "$2, $1"));

// Finds the first number that is at least three numbers long.
alert("2 to the 64th is 18446744073709551616.".findPattern("#{3,}", "ol"));

Answer 5

I write my own function, using c++ and boost::regex

std::string glob_to_regex(std::string val)
{
    boost::trim(val);
    const char* expression = "(\\*)|(\\?)|([[:blank:]])|(\\.|\\+|\\^|\\$|\\[|\\]|\\(|\\)|\\{|\\}|\\\\)";
    const char* format = "(?1\\\\w+)(?2\\.)(?3\\\\s*)(?4\\\\$&)";
    std::stringstream final;
    final << "^.*";
    std::ostream_iterator<char, char> oi(final);
    boost::regex re;
    re.assign(expression);
    boost::regex_replace(oi, val.begin(), val.end(), re, format, boost::match_default | boost::format_all);
    final << ".*" << std::ends;
    return final.str();
}

it looks like all works fine

Answer 6

no need for incomplete or unreliable hacks. there's a function included with python for this

>>> import fnmatch
>>> fnmatch.translate( '*.foo' )
'.*\\.foo$'
>>> fnmatch.translate( '[a-z]*.txt' )
'[a-z].*\\.txt$'