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I have a section in file:

[Source]

[Source.Ia32]


[Source.Ia64]

I have created the expression as:

const boost::regex source_line_pattern ("(Sources)(.*?)");

Now, I am trying to match the string, but I am not able to match; it is always returning 0.

if (boost::regex_match ( sToken, source_line_pattern ) )
  return TRUE;

Please note that sToken value is [Source]. [Source.Ia32]... and so on.

Thanks,

rainydaymatt
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user1553605
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2 Answers2

2

There are at least two problems with your code. First, the regular expression you give contains the literal string "Sources", and not "Source", which is what you seem to be trying to match. The second is that boost::regex_match is bound: it must match the entire string. What you seem to want is boost::regex_search. Depending on what you are doing, however, it might be better to try to match the entire string: "\\[Source(?:\\.(\\w+))?\\]\\s*". Which provides for capture of the trailing part, if present (but not the leading "Source"---no point, in general, in capturing something that is a constant).

Note too that the sequence ".*?" is very dubious. Normally, I would expect the regular expression parser to fail if a (non-escaped) '*' is followed by a '?'.

James Kanze
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    `.*?` means non-greedy repeat in Perl regex syntax, which is the default in `boost::regex`: http://www.boost.org/doc/libs/1_34_0/libs/regex/doc/syntax_perl.html – svk Jun 17 '13 at 14:30
  • I have added the regular expression "\\[Source(?:\.(\\w+))?\\]\\s*" but it is still returning 0. – user1553605 Jun 17 '13 at 15:13
  • @svk Ah. I didn't look it up, and just interpreted it as a `*` followed by a `?`, not as a single token `*?`. – James Kanze Jun 17 '13 at 15:41
  • @user1553605 From the string you quote, it doesn't look like you're escaping all of the `'\\'` correctly. (I missed one myself in my original posting---I've fixed that now.) In this particular case, all of the `'\\'` are for `boost::regex`, so all need to be doubled. – James Kanze Jun 17 '13 at 15:43
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The issue is that boost::regex_match only returns true if the entire input string is matched by the regex. So the '[' and ']' are not matched by your current regex, and it will fail.

Your options are either to use boost::regex_search, which will search for a substring of the input that matches your regex, or modify your regex to accept the entire string being passed in.

Dave S
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