What is a Regular Expression?

I have been programming for a couple of years, and I keep hearing people talk about regular expressions and perl like regular excpression. Java has an api for regular expression's, and I would just like some one to lay down the facts and explain to me what they are and how they are used.
Thanks. :)

http://developer.java.sun.com/developer/technicalArticles/releases/1.4regex/

Similar Messages

What is the regular expression for "__" ?

I just read through String and Pattern API, can't figure it out.
I want to go:
String.replaceFirst("__", "_");
i.e., replace the first 'double under-score' with a single underscore.
But it "__" is now a regular expression. Please help ! Thanks.

My mistake was I though it would change the
string...
text.replace(...)
should be
text = text.replace(...)A frequent mistake. I didn't notice, since I was focused on the regex aspect of the question.
� {�

What is the regular expression for the end of a story?

Forgive me if this is wrong forum for asking this, but I'm trying to use the Find command using GREP and I need to know the regular expression for the end of a story. (Or, the last character of a story.) Thanks in advance.

I'd try search for .\z (that's a dot in front) which ought to find the very last character in the story, and replace with $0 and your additional text.
You know you can use a keyboard shortcut to move your cursor to the end of any story, right? Ctrl + End on Windows, Cmd + End, I think, on Mac. Unless you want to do this to every single story in the document, I would think you might be just as well off to put your text on the clipboard, put the cursor in the story and hit the key combo followed by Ctrl/Cmd + V to paste.

Regular expressions in ActionScript??

I have been looking at the Adobe publication Programming Action Script (pdf) and it
specifies ECMA-262 3rd edition specification. But the specification don't seem to
state exactly what type of regular expression engine and version is used.
Is it POSIX, or PERL compatible regular expressions (or both)?
I have read and used the classic O'Reilly text Mastering Regular Expressions
and coded regular expressions in javascript/php/etc (anywhere regular expressions
could be use, Apache configuration file, other server config files, etc etc etc)
There is a difference in the type of engine used, where as performance is
concerned, as well as the range of syntax valid in a particular implementation.
Thank You
JK

http://www.regular-expressions.info/javascript.html

A regular expression

var wgCurRevisionId = "167969518";
I want to get
String s = "167969518";
while ((line=br.readLine())!=null){
                String s2 = line.replaceAll("\\s+[a-zA-Z]+\\s[a-zA-Z]+\\s=\\s+(\\d+),$1");
            }Can you point out what is wrong in my code?
Thanks!

Thanks, it works well in my code I posted in the forum.
I am parsing another line
<li>(cur) (<a href="/w/index.php?title=Spallation&diff=165653968&oldid=165464706" title="Spallation">last</a>) <input type="radio{code}
and to get a number
{code}165653968{code}
What is the regular expression?

String.split() regular expression

Regular expression escapes me. I have a line of a CSV file that looks like this:
1,,3,2,45.00,"This & That, LLC",0
I want the string split by commas but the problem with the line above is there's a comma in the name of the company...I obviously don't want the company name split in half...what would the regular expression be that I would provide to the split method to ensure that only commas not found in between double quotes are used to split the string into an array of Strings? is this possible?
Thanks in advance!
Rob

Telling someone to google might be deserved, but it is mean and unhelpful.
If you want to find a regex for CSV's see O'Reilly's "Mastering Regular Expressions" Section 8.4.4.3. Either buy the book - it's worth it - or subscribe to safari.

What's wrong with the regular expression?

Hi all,
For the life of me I can not figure out what is wrong with this regular expression
.*\bA specific phrase\.\b.*
This is just an example the actual phrase can be an specific phrase. My problem comes when the specific phrase ends in a period. I've escaped the period but it still gives me an error. The only time I don't get an error is when I take off the end boundry character which will not suffice as a solution. I need to be able to capture all the text before and after said phrase. If the phrase doesn't have a period it would look like this...
.*\bA specific phrase\b.*
which works fine. So what is it about the \.\b combination that is not matching?
I've been banging my head on this for a while and I'm getting nowhere.
The application highlights text that comes from a server. The user builds custom highlights that have some options. Highlight entire line, match partial word, and ignore case. The code that builds my pattern is here
String strHighlight = _strHighlight;
        strHighlight = strHighlight.replaceAll("\\*", "\\\\*");
        strHighlight = strHighlight.replaceAll("\\.", "\\\\.");
        String strPattern = strHighlight;
        if(_bEntireParagraph)
            if(_bPartialWord)
                strPattern = ".*" + strHighlight + ".*";
            else
                strPattern = ".*\\b" + strHighlight + "\\b.*";
        else
            if(_bPartialWord)
                strPattern = strHighlight;
            else
                strPattern = "\\b" + strHighlight + "\\b";
        if(_bIgnoreCase)
            _patHighlight = Pattern.compile(strPattern, Pattern.CASE_INSENSITIVE);
        else
            _patHighlight = Pattern.compile(strPattern);So for example I matching the phrase: The dog ate the cat. And that phrase came over in the following text: Look there's a dog. The dog ate the cat. "Oh my!"
And my user has the entire line and ignore case options selected then my regex woud look like this: .*\bThe dog ate the cat\b.*
That should get highlighted, but for some reason it doesn't. Correct me if I'm wrong but doesn't the regex read as follows:
any characters
word boundry
The dog ate the cat[period]
word boundry
any characters until newline.
Any help will be much appreciated

A word boundary (in the context of regexes) is a position that is either followed by a word character and not preceded by one (start of word) or preceded by a word character and not followed by one (end of word). A word character is defined as a letter, a digit, or an underscore. Since a period is not a word character, the only way the position following it could be a word boundary is if the next character is a letter, digit or underscore. But a sentence-ending period is always followed by whitespace, if anything, so it makes no sense to look for a word boundary there. I think, instead of \b, you should use negative lookarounds, like so: strPattern = ".*(?<!\\w)" + strHighlight + "(?!\\w).*";

Match Regular Expression does not match what Match Pattern does

I have read through a lot of posts about how Match Pattern does not match what Match Regular Expression will due to not processing some characters.
However, I found a problem with the other way. A simple Reg-Ex that works in Match Pattern but not Match Regular Expression.
What I have here is just an example. I want to use Match Regular Expression so I can specify some sub-matches.
The reg-ex is for: one or more non-numeric characters, a space, one or more numeric characters. At the start of the string.
How can I get this working in Match Regular Expression? I am working in LabVIEW 2010f2 32 bit. Here is the code snippet and the results:
Rob
Solved!
Go to Solution.

Robert Cole wrote:
I think I prefer the ~ for negation since ^ is also used for beginning of the string. But we work with what we have.
Let me offer you a tip and perhaps defend the honor of the regex a little bit. One of my favorite features of regexes is the ability to specify character classes (and their negation). One of the reasons I have to think about the ~ versus ^ is that I rarely use ^ in a regex alternative.
Some examples:
[0-9] = \d (digit)
[^0-9] = \D (not a digit)
The equivalent regex for your case is: \D+ \d+

What is regular expression for cheking a set operation

I want a regular expression for checking the syntax of the set operation given as input
ex:
the input should be
[1,2,3]+[2,3] or [1,2]-[2] or [1,2,3]*[1,2]
is should check the square bracket and the operator between two set operands

I think you should code that from scratch. When you validate input, you usually want to tell the user what they did wrong, but a regex will only tell you whether it matches or not.

What regular expression

I have a problem with a regular expression. The objective is to find each word that does not begin with a capital letter. I don't know what regex to use. So far I have this:
[a-z]+but that cuts off the first (capital) letter and returns also such cut words. I appreciate all help.
PR.

Aardenon wrote:
I have a problem with a regular expression. The objective is to find each word that does not begin with a capital letter. I don't know what regex to use. So far I have this:
[a-z]+
You need to read up on "boundary" meta-characters. Try [url http://download.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html#sum]here for starters; although you'd probably be even better to go through [url http://download.oracle.com/javase/tutorial/essential/regex/]the tutorial.
Winston

What, no regular expressions?

I was porting a CGI to use Oracle as a backend instead of
PostgreSQL. When I couldn't find any regular expression
facilities in Oracle, I reconsidered and ended up waiting for the
next release of PostreSQL.
Still, Oracle was startlingly fast and can do things PostgreSQL
can't (a VIEW based on a UNION ALL, and a column based on a
subselect).
Maybe Sybase has regexps, but I won't find out till I have some
more spare time.
null

JoeD. wrote:
> Greetings all. I'm having a heckofa problem and I was
hoping someone on these
> boards may be able to help. I have 1000s links that I
need to process and I
> dread doing this by hand.
Why don't you simplify your request?
This is what I have: <a
href="xxx.php?blah">text</a>
This is what I want: <a href="xxx.html">text</a>
It's my guess that this would be very easy, but give us
examples of
before and after.
Mick
Many of the links are now bad links?and they are
> 'bad' in a very predictable way as they call contain
'php?title=' ? so I want
> to search for the bad link code and simply strip the
<anchor> tag and leave the
> containing text as is. My guess is that this shouldn't
be as difficult as it
> is, but I could be very wrong here. So, I've done the
following in the
> Find/Replace dialog: Search: Specific Tag Selected Tag:
A With Attribute:
> HREF Here is where I get confused. The 'with attribute'
option has '=, <, >,
> !=' as the optoins. So I tried the equality operator
using both regular
> expressoins (*php\?title\=*) and without regular
expressions(php?title), but no
> matter what I do, none of the links are being found. I'm
very new to regex so
> maybe maybe my code here is bad. I wish there was a
'containing' option that
> with attribute exposed, but there isn't. So: do any of
y'all DW gurus have
> any ideas about this? I'm pulling what little hair I
have left out over this.
> Thanks, Joe
>

Help in regular expression matching

I have three expressions like
1) [(y2009)(y2011)]
2) [(y2008M5)(y2011M3)] or [(y2009M5)(y2010M12)]
3) [(y2009M1d20)(y2011M12d31)]
i want regular expression pattern for the above three expressions
I am using :
REGEXP_LIKE(timedomainexpression, '???[:digit:]{4}*[:digit:]{1,2}???[:digit:]{4}*[:digit:]{1,2}??', 'i');
but its giving results for all above expressions while i want different expression for each.
i hav used * after [:digit:]{4}, when i am using ? or . then its giving no results. Please help in this situation ASAP.
Thanks

I dont get your question Can you post your desired output? and also give some sample data.
Please consider the following when you post a question.
1. New features keep coming in every oracle version so please provide Your Oracle DB Version to get the best possible answer.
You can use the following query and do a copy past of the output.
select * from v$version 2. This forum has a very good Search Feature. Please use that before posting your question. Because for most of the questions
that are asked the answer is already there.
3. We dont know your DB structure or How your Data is. So you need to let us know. The best way would be to give some sample data like this.
I have the following table called sales
with sales
as
      select 1 sales_id, 1 prod_id, 1001 inv_num, 120 qty from dual
      union all
      select 2 sales_id, 1 prod_id, 1002 inv_num, 25 qty from dual
select *
from sales 4. Rather than telling what you want in words its more easier when you give your expected output.
For example in the above sales table, I want to know the total quantity and number of invoice for each product.
The output should look like this
Prod_id   sum_qty   count_inv
1         145       2 5. When ever you get an error message post the entire error message. With the Error Number, The message and the Line number.
6. Next thing is a very important thing to remember. Please post only well formatted code. Unformatted code is very hard to read.
Your code format gets lost when you post it in the Oracle Forum. So in order to preserve it you need to
use the {noformat}{noformat} tags.
The usage of the tag is like this.
<place your code here>\
7. If you are posting a *Performance Related Question*. Please read
   {thread:id=501834} and {thread:id=863295}.
   Following those guide will be very helpful.
8. Please keep in mind that this is a public forum. Here No question is URGENT.
   So use of words like *URGENT* or *ASAP* (As Soon As Possible) are considered to be rude.

Bracket in Regular Expression constant?

I am a bit puzzled by the behavior I am experiencing in LV 2011. I hope to get some light from experts out there.
I am trying to parse a messy ASCII header file and after having split it into individual lines (strings), I use the "Match Regular Expression" function to remove some of the info before the substantial information.
Some of the strings include square brackets ([, ]), which are special characters for the function, therefore, as documented in the help, one needs to precede them with a backslash.
Example:
I want to parse the following line:
#PR [PR_DEV,I,2]
One way (which I am using because of considerations related to the rest of the header) is the the following:
Note that the first string constant is using "Code Display" whereas the second one is using "Normal Display".
Why did I not put a backslash in front of the bracket in the first string, you may ask? Well, I did, but it disappeared after I typed the other characters. And reverting to "Normal Display" did not restore it.
Of course, the first version does not parse the input string correctly, whereas the second one does it fine.
In other words, the custom display string (which is convenient for cryptic codes such as \s* or to distinguish between space and tab...or simply ENTER tabs!) seems to mess up with the \[ combo (likewise with the \] one).
It is not a huge deal. I can use the "Normal Display" mode, but I tend to think that this qualifies as a hidden "feature". And again, it is still a pain in the ... when dealing with special characters such as tabs, etc...
Solved!
Go to Solution.

I think that [ is a special character which needs to be preceded by a backslash, but it is not one of the defined backslash characters (like \s). So, you need to put in two \\ to get one \ while in '\' Codes Display.
You can put in any character by using \xx where the xx is a hex character using only upper case letters for A..F. I converted the strings to byte arrays and tried to see what made the arrays match and the Match work.
Lynn

Help with Regular Expression for field validation

I'm fairly new to using regular expressions and using Acrobat. This is probably a simple question, but I've been unable to figure it out.
I have a text field on a PDF that I would like to be 9 characters in length. The first 2 characters can only be alphanumeric, the last 7 characters can only be numeric.
At first I was using the following, which allows all the characters to be alphanumeric:
var re = /^[A-Za-z0-9 :\\_]$/;
if (event.change.length >0) {
if (event.willCommit == false) {
    if (!re.test(event.change)) {
        event.rc = false
That works fine, but it's not quite what I needed. With some assistance I changed it (see below) to fit what I was looking for. However, this didn't work; it prevents anything from being entered in the field:
var re = /^[A-Za-z0-9]{2}\d{7}$/;
if (event.change.length >0) {
if (event.willCommit == false) {
    if (!re.test(event.change)) {
        event.rc = false
Any help would be greatly appreciated.
Thanks...

Here's a function you can call form the field's custom Format script. It should be placed in a document-level JavaScript:
function custom_ks1() {
    // Define non-commited regular expression
    var re = /^[A-Za-z0-9]{0,2}([0-9]{0,7})?$/;
    // Get all of the characters the user has entered
    var value = AFMergeChange(event);
    // Allow field to be cleared
    if(!value) return;
    if (event.willCommit) {
        // Define commited regular expression
        var re = /^[A-Za-z0-9]{2}[0-9]{7}$/;
        if (!re.test(value)) { // If final value doesn't match, alert user
            app.alert("Your error message goes here.");
            // event.rc = false
    } else { // not commited
        // Only allow characters that match the regular expression
        event.rc = re.test(value);
Call it like this:
// Custom Keystroke script
custom1_ks();

Unix Log Monitoring regular expression not picking up alerts

Hi,
We are moving our unix monitoring to SCOM 2012 SP1 rollup 4.
What I have got working is indvidual alert logging of Unix Log alerts by exporting the MP and changing the <IndividualAlerts> value to true and removing the suppression xml section then reimporting the MP.
What I am trying to do is use the regular expression to peform the suppression of specific event (such as event codes).
The expression is:
((?i:warning)(?!(.*1222)|(.*1001)))
ie Search the log for "warning" (not case sensitive) then check if events 1222 or 1001 exist if so return no match, if they dont exist then return true.
I use the built in test function in SCOM when creating the rule and the tests come back as expected but when I inject test lines into the unix log, no alerts get generted.
I suspect it could be the syntax not being accepted on the system (its running RedHat 6 )
I have tested this with regex tools and works.
When I try and test it on the server i get:
[root@bld02 ~]# grep ((?i:Warning)(?!(.*1222)|(.*1001))) /var/log/messages
-bash: !: event not found
[root@bld02 ~]# tail /var/log/messages
Nov 13 15:07:26 bld02 root: SCOM Test Warning Event ID 1001 Round 18
Nov 13 15:07:29 bld02 root: SCOM Test Warning Event ID 1000 Round 18
Nov 13 15:07:35 bld02 root: SCOM Test Warning Event ID 1002 Round 18
So I am expecting 2 alerts to be generated.
SCOM tests to show expression working:
Test 1 Matching
Test 2 to exclude
Need some help with this, Thankyou in advance :)

Hello,
Here's an example of modifying the MP to exclude particular events. Firstly, I created a log file rule using the MP template that is fairly inclusive - matching the string Warning (with either a lower or upper case W).
I then exported the MP, and modified the rule. I set the IndividualAlerts = true and removed the AlertSuppression element, so that every matched line will fire a unique alert. You don't have to remove the AlertSuppression, but you should use
Individual alerts so that the exclusion logic doesn't exclude concurrent events that you actually want to match.
Implementing the exclusion logic involves the addition of a System.ExpressionFilter definition in the rule. This will use a conditional evaluation of the //row element of the data item. Here's an example of a dataitem matching an individual row:
<DataItem type="System.Event.Data"time="2013-11-15T10:33:14.8839662-08:00"sourceHealthServiceId="667FF365-70DD-6607-5B66-F9F95253B29F">
<EventOriginId>{86AB962D-2F44-29FD-A909-B99FF6FEB2C5}</EventOriginId>
<PublisherId>{EC7EA4B1-0EA5-7E8E-701F-82FEF3367BC4}</PublisherId>
<PublisherName>WSManEventProvider</PublisherName>
<EventSourceName>WSManEventProvider</EventSourceName>
<Channel>WSManEventProvider</Channel>
<LoggingComputer/>
<EventNumber>0</EventNumber>
<EventCategory>3</EventCategory>
<EventLevel>0</EventLevel>
<UserName/>
<RawDescription>Detected Entry: warning 1002</RawDescription>
<CollectDescription Type="Boolean">true</CollectDescription>
<EventData>
<DataItem type="SCXLogProviderDataSourceData"time="2013-11-15T10:33:14.8839662-08:00"sourceHealthServiceId="667FF365-70DD-6607-5B66-F9F95253B29F">
<SCXLogProviderDataSourceData>
<row>warning 1002</row>
</SCXLogProviderDataSourceData>
</DataItem>
</EventData>
<EventDisplayNumber>0</EventDisplayNumber>
<EventDescription>Detected Entry: warning 1002</EventDescription>
</DataItem>
Here is the rule in the MP XML. The <ConditionDetection>...</ConditionDetection> content was what I added to do the exclusion filtering:
<Rule ID="LogFileTemplate_66b86eaded094c309ffd2631b8367a32.Alert" Enabled="false" Target="Unix!Microsoft.Unix.Computer" ConfirmDelivery="false" Remotable="true" Priority="Normal" DiscardLevel="100">
<Category>EventCollection</Category>
<DataSources>
<DataSource ID="EventDS" TypeID="Unix!Microsoft.Unix.SCXLog.VarPriv.DataSource">
<Host>$Target/Property[Type="Unix!Microsoft.Unix.Computer"]/PrincipalName$</Host>
<LogFile>/tmp/test</LogFile>
<UserName>$RunAs[Name="Unix!Microsoft.Unix.ActionAccount"]/UserName$</UserName>
<Password>$RunAs[Name="Unix!Microsoft.Unix.ActionAccount"]/Password$</Password>
<RegExpFilter>warning</RegExpFilter>
<IndividualAlerts>true</IndividualAlerts>
</DataSource>
</DataSources>
<ConditionDetection TypeID="System!System.ExpressionFilter" ID="Filter">
<Expression>
<RegExExpression>
<ValueExpression>
<XPathQuery Type="String">//row</XPathQuery>
</ValueExpression>
<Operator>DoesNotContainSubstring</Operator>
<Pattern>1001</Pattern>
</RegExExpression>
</Expression>
</ConditionDetection>
<WriteActions>
<WriteAction ID="GenerateAlert" TypeID="Health!System.Health.GenerateAlert">
<Priority>1</Priority>
<Severity>2</Severity>
<AlertName>Log File Alert: ExclusionExample</AlertName>
<AlertDescription>$Data/EventDescription$</AlertDescription>
</WriteAction>
</WriteActions>
</Rule>
I traced this with the Workflow Analyzer as I tested, which shows the logic being applied. Here is the exclusion happening:
Here's more info on the definition of an ExpressionFilter:
http://msdn.microsoft.com/en-us/library/ee692979.aspx
And more information on Regular Expressions in MPs:
http://support.microsoft.com/kb/2702651/en-us
You can also have multiple Expressions in the ExpressionFilter joined by OR or AND operators.
Also, if you are comfortable with the MP authoring, you can just skip the step of creating the rules in the MP template and just author your own MP with the VSAE tool:
http://social.technet.microsoft.com/wiki/contents/articles/18085.scom-2012-authoring-unixlinux-log-file-monitoring-rules.aspx
www.operatingquadrant.com

What is a Regular Expression?

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