Help building a regex

Question

I need to build a regular expression that finds the word "int" only if it's not part of some string.

I want to find whether int is used in the code. (not in some string, only in regular code)

Example:

int i;  // the regex should find this one.
String example = "int i"; // the regex should ignore this line.
logger.i("int"); // the regex should ignore this line. 
logger.i("int") + int.toString(); // the regex should find this one (because of the second int)

thanks!

The regex should work in Java or do you apply the expression on Java code? — Felix Kling, Jun 26 '11 at 14:39
Is it require to parse file for check GRAMMAR of program in that case it is easy - just ignore int if it is started with 'String' token and ended by ';' — Kamahire, Jun 26 '11 at 14:46
http://stackoverflow.com/questions/731015/is-there-a-way-using-regular-expressions-to-match-a-pattern-for-text-outside-of — Martijn Courteaux, Jun 26 '11 at 14:54
http://stackoverflow.com/questions/1443360/regex-for-matching-a-character-but-not-when-its-enclosed-in-quotes — Martijn Courteaux, Jun 26 '11 at 14:55
http://stackoverflow.com/questions/1060616/how-can-regex-ignore-escaped-quotes-when-matching-strings — Martijn Courteaux, Jun 26 '11 at 14:57
@Martijn Courteaux: It looks like 'close as duplicate' would be appropriate (rather than just listing the related questions). — phooji, Jun 27 '11 at 03:08
@Martijn Courteaux: Fair enough. I guess none of them are 100% overlapping anyway. — phooji, Jun 28 '11 at 18:22

Bohemian · Accepted Answer · 2011-06-27T03:00:53.823

It's not going to be bullet-proof, but this works for all your test cases:

(?<=^([^"]*|[^"]*"[^"]*"[^"]*))\bint\b(?=([^"]*|[^"]*"[^"]*"[^"]*)$)

It does a look behind and look ahead to assert that there's either none or two preceding/following quotes "

Here's the code in java with the output:

    String regex = "(?<=^([^\"]*|[^\"]*\"[^\"]*\"[^\"]*))\\bint\\b(?=([^\"]*|[^\"]*\"[^\"]*\"[^\"]*)$)";
    System.out.println(regex);
    String[] tests = new String[] { 
            "int i;", 
            "String example = \"int i\";", 
            "logger.i(\"int\");", 
            "logger.i(\"int\") + int.toString();" };

    for (String test : tests) {
        System.out.println(test.matches("^.*" + regex + ".*$") + ": " + test);
    }

Output (included regex so you can read it without all those \ escapes):

(?<=^([^"]*|[^"]*"[^"]*"[^"]*))\bint\b(?=([^"]*|[^"]*"[^"]*"[^"]*)$)
true: int i;
false: String example = "int i";
false: logger.i("int");
true: logger.i("int") + int.toString();

Using a regex is never going to be 100% accurate - you need a language parser. Consider escaped quotes in Strings "foo\"bar", in-line comments /* foo " bar */, etc.

score 0 · Answer 2 · answered Jun 26 '11 at 14:44

0

Not exactly sure what your complete requirements are but

$\s*\bint\b

perhaps

answered Jun 26 '11 at 14:44

MeBigFatGuy

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score 0 · Answer 3 · answered Jun 26 '11 at 14:57

0

Assuming input will be each line,

^int\s[\$_a-bA-B\;]*$

it follows basic variable naming rules :)

answered Jun 26 '11 at 14:57

Ratna Dinakar

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score 0 · Answer 4 · answered Jun 26 '11 at 15:12

If you think to parse code and search isolated int word, this works:

(^int|[\(\ \;,]int)

You can use it to find int that in code can be only preceded by space, comma, ";" and left parenthesis or be the first word of line.

You can try it here and enhance it http://www.regextester.com/

PS: this works in all your test cases.

score 0 · Answer 5 · answered Jun 26 '11 at 15:57

0

$[^"]*\bint\b

should work. I can't think of a situation where you can use a valid int identifier after the character '"'. Of course this only applies if the code is limited to one statement per line.

answered Jun 26 '11 at 15:57

jzilla

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Help building a regex

5 Answers5