regular expression to find meta value

Question

i am trying to read from a webpage and get the last modified date from meta. for example

<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta http-equiv="last-modified" content="Mon, 17 Sep 2012 13:57:35 SGT" />
</head>

i am reading line by line, how can i build the regex in this case? I am fairly new to the regex. i have tried

line.matches("<meta http-equiv=\"last-modified\" content=\"(\w)*\" /> ");

but do not think it is correct.

Usually people will say regex is not the right tool for HTML, but in this case, there should be no nested tags, so it should be fine. `/\/` something like that. — Orbling, Sep 27 '12 at 17:11
b) [Parsing HTML is not a task for regexes](http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/1732454#1732454) — Martin Ender, Sep 27 '12 at 17:12
Don't use regex as it is an overkill for this job. Just find the matching tag, and read after `content="` — nullpotent, Sep 27 '12 at 17:12
@Orbling the attributes could still be in a different order. And you can't be sure that the tags will always be on their own line. — Martin Ender, Sep 27 '12 at 17:12
It's fine in this case to use regex, it's just plucking attributes out of a tag. — Orbling, Sep 27 '12 at 17:12
@m.buettner: The attributes being in alternate order can be handled if needed. The content might be in a regular layout anyhow. — Orbling, Sep 27 '12 at 17:13
Sure... as can be lots of things in HTML. I'm usually the first one to check out whether a **specific** HTML problem can't be solved with regex. But still it's fair to note, that a 100% working version with regex isn't as easy as you'd think at first glance. — Martin Ender, Sep 27 '12 at 17:14
@m.buettner: Aye, which is why I caveated my comment with "in this case", regex is frequently not the best candidate for this sort of task. But parsing a full DOM structure can be overkill too. — Orbling, Sep 27 '12 at 17:15
@user1275129: the problem with your attempt is, that \w only matches `[a-zA-Z0-9_]` ... but you also need `,:` and whitespace — Martin Ender, Sep 27 '12 at 17:16

score 1 · Accepted Answer · edited May 23 '17 at 12:18

1

While you should never use regex to parse html, if you insist upon it, heres a regex option

Pattern metaPattern = Pattern.compile("meta .*\"last-modified\" content="(.*)");
Matcher metaMatch = metaPattern.matcher(sampleString);
if metaMatch.matches()
{
    System.out.println(metaMatch.group(1));
}

edited May 23 '17 at 12:18

Community

1
1

answered Sep 27 '12 at 17:25

Tadgh

1,999
10
23

ty, i also found out this String metaRegex=""; final Pattern metapa = Pattern.compile(metaRegex, Pattern.DOTALL); final Matcher metamatch = metapa.matcher(html); String lastmodified=null; if (metamatch.find()) { lastmodified=metamatch.group(1); } – onegun Sep 27 '12 at 17:43

score 0 · Answer 2 · answered Sep 27 '12 at 17:20

0

You can't use \w only for your group, since your target information contains non-word characters.

Try something like:

String line = "<meta http-equiv=\"last-modified\" content=\"Mon, 17 Sep 2012 13:57:35 SGT\" />";

Pattern p = Pattern.compile("<meta .*last-modified.*content=\"(.*)\".*");
Matcher m = p.matcher(line);
if (m.matches())
    System.out.println(m.group(1));

Output:

Mon, 17 Sep 2012 13:57:35 SGT

answered Sep 27 '12 at 17:20

pb2q

58,613
19
146
147

Even if he only gets one line at a time, you should probably make that `.*` ungreedy. – Martin Ender Sep 27 '12 at 17:21
ty, because Tadgh answered earlier, so i picked his, but your answer is good too – onegun Sep 27 '12 at 17:44

score 0 · Answer 3 · answered Sep 27 '12 at 18:27

And here's a solution with no regex.

Of course, you would have to be careful using this and do some checks beforehand.

String data = "<head>" +  
              "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=windows-1252\">" +
              "<meta http-equiv=\"last-modified\" content=\"Mon, 17 Sep 2012 13:57:35 SGT\" />" + 
              "</head>";

String key =  "<meta http-equiv=\"last-modified\" content=\"";

int from = data.lastIndexOf(key);
String tag = data.substring(from + key.length());
int to = tag.indexOf("\"");
String date = tag.substring(0, to);
System.out.println(date);

regular expression to find meta value

3 Answers3