preg_match question

wanaka

any idea why it return nothing as it suppose to return myserver.esc

<?php
$str="PROBLEM esc_mon myserver.esc: File System Full: /tmp on esc_mon (Newmon for ESC)";
function string_cut($string,$cut_size)
{
$StringArray=explode(" ",$string);
for($i=0;$i<$cut_size;$i++)
{
$string_cut.=" "."$StringArray[$i]";
}
return "$string_cut";
}
$string="";

$str = string_cut($str,3);

if ((preg_match("/esc_mon/i", $str)) == true)
{
if ((preg_match("/.esc:/", $str)) == true)
{
$pattern = "§.esc_mon\s(.?)\s§i";
$found = preg_match($pattern,$str,$matches);
if($found > 0) $hostname = $matches[1];
echo "$hostname";
echo "Get it";
}
else
{
$hostname = "esc_mon";
}
}
else {
$pattern = "§problem\s(.*?)\s§i";
$found = preg_match($pattern,$str,$matches);
if ($found > 0) $hostname = $matches[1];
echo "$hostname";
}

BuzzLY

Try this pattern instead:

$pattern = "§esc_mon\s([\S]*)§i";

That will work whether you use your string_cut function or not.

You should try to keep your discussions in one thread. I realize I did not answer your other thread right away, but creating a new thread with the same question is not the correct way to get your questions answered.

I strongly recommend you take the time to learn regular expressions. If you knew even a little about them, you would have realized that \s is a modifier that means "whitespace." Since you cut your string, it wasn't finding your text, because there was no whitespace after the text it was looking for.

I'm not chastising you for your lack of knowledge. I'm simply recommending you learn a little about regexp if you plan on using them extensively. Otherwise, you will be in here asking for patterns every time your requirements change, and that can be frustrating for you as well as annoying for anyone answering your queries.

Start with these:

http://www.amk.ca/python/howto/regex/
http://sitescooper.org/tao_regexps.html
http://www.english.uga.edu/humcomp/perl/regex2a.html
http://www.english.uga.edu/humcomp/perl/regexps.html
http://www.english.uga.edu/humcomp/perl/regular_expressions.HTML
http://www.english.uga.edu/humcomp/perl/
http://java.sun.com/docs/books/tutorial/extra/regex/
http://gnosis.cx/publish/programming/regular_expressions.html
http://www.zvon.org/other/PerlTutorial/Books/Book1/
http://it.metr.ou.edu/regex/
http://www.regular-expressions.info/

wanaka

Hi ,

Thanks for your help. Just wondering the regexp that you mention what is the meaning of [\S]*

BuzzLY

PCRE Pattern Syntax

"§esc_mon\s([\S]*)§i" broken down:

§ - delimiter (open)
esc_mon - the term after which you want to find a word
\s - whitespace character (space, in your case)
() - grouping for backreference
[] - character class (for example, [a-z] matches any lower case letter
\S - opposite of \s, or any character EXCEPT whitespace
* - match 0 or more occurances of previous term, in this case [\S]
§ - delimiter (close)
i - case insensitive match. Not really needed in this case, but I use it as a matter of habit.

Hope that helps... now USE THE MANUAL 😉

wanaka

Hi,

I have noticed that if str is like "PROBLEM esc_mon.ESC 10.30.6.134: Interface 3 down (Newmon for ESC)" it will return the IP address correctly. But if the str is "PROBLEM esc_mon 10.30.6.134: Interface 3 down (Newmon for ESC)" it will return nothing at all.

$hostname=findhost($str);
echo $hostname;

I try put this three line and it return the ip address correctly. I was very curios is it something to do with my if condition

$pattern = "§esc_mon\s([\S]*)§i";
$found = preg_match($pattern,$str,$matches);
echo "$matches[1]";

BuzzLY

Make sure you always enclose your code with [php] and [/php] tags. It's MUCH easier to read that way.

Your problem is probably this:

else ((preg_match("§esc_mon.esc\s([\S]*)§i", $str)) == true); 

   //  should be: 

else if (preg_match("§esc_mon.esc\s([\S]*)§i", $str));

FYI, preg_match returns either 0 (for no match found), or the number of matches found (always 1, since it stops after finding the first match). It does not return TRUE or FALSE.

It is true that 0 is equal to FALSE, and 1 is equal to TRUE. However, they are not identical, and it is not good coding practice to treat them the same. If a function returns a 0 or 1, then test for 0 or 1, don't test for TRUE or FALSE.

I will sometimes use a shortcut, like above, "if($condition) {" -- if $condition is TRUE, or any value above 1, the condition is satisfied. But if $condition returns a number, I never compare it to TRUE, because even though that would evaluate properly, they are not identical.

When testing for an actual TRUE or FALSE condition, use the Identical operator (===). Sometimes a function like strpos() will return 0 to indicate that it found the character at the beginning of the string. If you use the shortcut "if(!strpos($string, $needle)) {" it will incorrectly skip your code if your $needle is found at the beginning of string. Instead, use "if(strpos($string, $needle) === FALSE) {"