Regular expressions and input streams
Hello,
I am trying to find a way to read characters from a stream and find matches in them with regular expressions. The problem is that the stream may contain a big amount of characters, so I can't read all of them, keep them in a big string, and then perform the searches. Is there a way to perform searches while I read the characters? I scanned the documentation of Pattern and Matcher and found nothing that can help.
Any ideas?
Thanks.
Looking at the method
public Matcher Pattern.matcher(CharSequence input);
one could be excused for assuming that one could turn an InputStream into a CharSequence object since a 'stream' implies sequencial access and CharSequence sounds like it provides sequential access.
This would just require the implementation of 4 method of which two (toString() and subSequence()) could probably be ignored BUT the method you wouild have to implement are charAt() and length() which imply random access rather than sequencial access!
Using the built in regex your problem looks difficult. If you are just looking for 'equality' matches (simple searching) then you could use Knuth-Morris-Pratt algorithm or the Boyer-Moore algorithm.
Similar Messages
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I have working regular expressions and a working sql connection, but I don�t know how to stop the info from getting into the database when input doesent match the regular expression.
For instans, you put in an e-mail without an "@" and my program writes and error message. But the info still gets in to the database.
Any help would be much apreciated as I dont know where to start. If you have links or code examples that would be great to.
Thanx.Well, the obvious answer is "only write the data to the database if the input doesn't match the regular expression."
Presumably you're really asking how to do that - but it depends upon how your application is structured in the first place, and you haven't told us anything at all about that. -
Juniper MX Regular expressions and user permissions ACS 5.4
Hi everyone!
Im having some trouble with regular expressions and permissions on our Juniper MX routers through ACS 5.4, and i would like some insight/help/poitners!!
We have a team of engineers that should only have read only permissions (important: show configuration) and also be able to just change the description on interfaces.
Thus far with the following regular expressions set for the shell profile they are going through i have managed the above, however the problem is when an engineer inputs "Show configuration", only the interfaces descriptions configuration is shown! The rest of the configuration will not be printed.
deny-commands1=.*.
allow-commands1=configure
deny-configuration1=.*.
allow-commands2=interfaces .*. description .*$
allow-configuration1=interfaces .*. description .*$
allow-commands2=show configuration.*
allow-commands3=show configuration
(some of these regex i know that are not needed, i was just playing around to check everything before posting)
Any pointers as to why or how to resolve this?
example output with the above:
show configuration
## Last commit: 2014-01-09 09:34:44 EET by someone
interfaces {
xe-0/0/0 {
xe-0/0/1 {
description xxxx;
xe-0/1/0 {
description xxxx;
xe-0/1/1 {
description xxxx;
xe-0/2/0 {
disable;
xe-0/2/1 {
description xxxx;
xe-0/3/0 {
description xxxx;
xe-0/3/1 {
description xxxx;
ae0 {
description "xxxx";
ae1 {
description xxxx;
demux0 {
lo0 {
{master}
Thanks in advance!
SpyrosYou are absolutely right!! I was doing research online after posting the above. The correct RADIUS attribute to use is actually CVPN3000/ASA/PIX7.x-Group-Based-Address-Pools. Then create the pool in ASA, and call that pool's name in ACS under that RADIUS attribute. Someone explained this perfectly in this community before. Much appreciate your answer!
Here's from another post last year:
ACS 5 does not have the feature of IP pools. Logically its always good to setup pools locally on vpn server and if you want user to pick ip from specific local pool you can configure acs to push that attribute.
On ACS Go to > Policy Elements -> Network Access -> Authorization Profiles -> Create ->
Name of the Policy ->Dictionary Type: Radius-Cisco VPN 3000/ASA/PIX7.x
Attribute Type : CVPN3000/ASA/PIX7.x-Group-Based-Address-Pools
Attribute Type: String
Attribute Value : Static MYPOOL (Name of the Pool which is defined on the ASA)
Access Policies ->Default Network Access -> Authorization -> Create -> Under result section call the Authorization p -
"Match Regular Expression" and "Match Pattern" vi's behave differently
Hi,
I have a simple string matching need and by experimenting found that the "Match Regular Expression" and "Match Pattern" vi's behave somewhat differently. I'd assume that the regular expression inputs on both would behave the same. A difference I've discovered is that the "|" character (the "vertical bar" character, commonly used as an "or" operator) is recognized as such in the Match Regular Expression vi, but not in the Match Pattern vi (where it is taken literally). Furthermore, I cannot find any documentation in Help (on-line or in LabVIEW) about the "|" character usage in regular expressions. Is this documented anywhere?
For example, suppose I want to match any of the following 4 words: "The" or "quick" or "brown" or "fox". The regular expression "The|quick|brown|fox" (without the quotes) works for the Match Regular Expression vi but not the Match Pattern vi. Below is a picture of the block diagram and the front panel results:
The Help says that the Match Regular Expression vi performs somewhat slower than the Match Pattern vi, so I started with the latter. But since it doesn't work for me, I'll use the former. But does anyone have any idea of the speed difference? I'd assume it is negligible in such a simple example.
Thanks!
Solved!
Go to Solution.Yep-
You hit a point that's frustrated me a time or two as well (and incidentally, caused some hair-pulling that I can ill afford)
The hint is in the help file:
for Match regular expression "The Match Regular Expression function gives you more options for matching
strings but performs more slowly than the Match Pattern function....Use regular
expressions in this function to refine searches....
Characters to Find
Regular Expression
VOLTS
VOLTS
A plus sign or a minus sign
[+-]
A sequence of one or more digits
[0-9]+
Zero or more spaces
\s* or * (that is, a space followed by an asterisk)
One or more spaces, tabs, new lines, or carriage returns
[\t \r \n \s]+
One or more characters other than digits
[^0-9]+
The word Level only if it
appears at the beginning of the string
^Level
The word Volts only if it
appears at the end of the string
Volts$
The longest string within parentheses
The first string within parentheses but not containing any
parentheses within it
\([^()]*\)
A left bracket
A right bracket
cat, cag, cot, cog, dat, dag, dot, and dag
[cd][ao][tg]
cat or dog
cat|dog
dog, cat
dog, cat cat dog,cat
cat cat dog, and so on
((cat )*dog)
One or more of the letter a
followed by a space and the same number of the letter a, that is, a a, aa aa, aaa aaa, and so
on
(a+) \1
For Match Pattern "This function is similar to the Search and Replace
Pattern VI. The Match Pattern function gives you fewer options for matching
strings but performs more quickly than the Match Regular Expression
function. For example, the Match Pattern function does not support the
parenthesis or vertical bar (|) characters.
Characters to Find
Regular Expression
VOLTS
VOLTS
All uppercase and lowercase versions of volts, that is, VOLTS, Volts, volts, and so on
[Vv][Oo][Ll][Tt][Ss]
A space, a plus sign, or a minus sign
[+-]
A sequence of one or more digits
[0-9]+
Zero or more spaces
\s* or * (that is, a space followed by an asterisk)
One or more spaces, tabs, new lines, or carriage returns
[\t \r \n \s]+
One or more characters other than digits
[~0-9]+
The word Level only if it begins
at the offset position in the string
^Level
The word Volts only if it
appears at the end of the string
Volts$
The longest string within parentheses
The longest string within parentheses but not containing any
parentheses within it
([~()]*)
A left bracket
A right bracket
cat, dog, cot, dot, cog, and so on.
[cd][ao][tg]
Frustrating- but still managable.
Jeff -
Regular Expression and PL/SQL help
I am using Oracle 9i, does 9i support regular expression? What functions are there?
My problem is the birth_date column in my database comes from teleform ( a scan program that reads what people wrote on paper), so the format is all jacked up.... 50% of them are 01/01/1981, 10% are 5/14/1995, 10% are 12/5/1993, 10% are 1/1/1983, 10% are 24-JUL-98. I have never really used regular expression and pl/sql, can anybody help me convert all of them to 01/01/1998?
Does Oralce 9i support regular expression? What can I do if oralce 9i does not support regular expression? Thank you very much in advance.9i doesn't support regular expressions (at least not in the 10g regular expressions sense. There is an OWA_PATTERN_MATCH package that has some facilities for regular expressions). But it doesn't look like this is a regular expressions problem.
Instead, this is probably a case where you need to
- enumerate the format masks you want to try
- determine the order you want to try them
- write a small function that tries each format mask in succession until one matches.
Of course, there is no guarantee that you'll ever be able to convert the data to the date that the user intended because some values will be ambiguous. For example, 01/02/03 could mean Feb 1, 2003 or Jan 2, 2003 or Feb 3, 2001 depending on the person who entered the data.
Assuming you can define the order, your function would just try each format mask in turn until one generated a valid date, i.e.
BEGIN
BEGIN
l_date := TO_DATE( p_string_value, format_mask_1 );
RETURN l_date;
EXCEPTION
WHEN OTHERS THEN
NULL;
END;
BEGIN
l_date := TO_DATE( p_string_value, format_mask_2 );
RETURN l_date;
EXCEPTION
WHEN OTHERS THEN
NULL;
END;
BEGIN
l_date := TO_DATE( p_string_value, format_mask_3 );
RETURN l_date;
EXCEPTION
WHEN OTHERS THEN
NULL;
END;
BEGIN
l_date := TO_DATE( p_string_value, format_mask_N );
RETURN l_date;
EXCEPTION
WHEN OTHERS THEN
NULL;
END;
RETURN NULL;
END;Justin -
Regular expressions and backreference
Hello!
I am trying to use backreferences in REGEXP in the PERL-style, where I want to match my regular expression and later refer to the grouped values. I can read that those are referecenced with \1 .. \9, but I simply cant get it to work. Here is an example in PL/SQL:
SELECT REGEXP_SUBSTR(l_users.adresse,'([A-Z]+)\s+(\d+)')
INTO l_dummy_varchar2
FROM dual;
OR I could do things like:
l_dummy_varchar2 := REGEXP_SUBSTR(l_users.adresse,'([A-Z]+)\s+(\d+)');
It seems to work, but I cant figure out how to get the backreferenced value.
I would love to do things like:
dbms_output.put_line('my value ='||\1)
but this doesnt work.
Help is very much appreciated.
Best regards
DannieLikewise you can extract things using the
REGEXP_SUBSTR, but you don't need back
referencing...backreferencing is better than additional function (ltrim) use, and BTW be careful with this "ltrims":
SQL> set serveroutput on
SQL>
SQL> DECLARE
2 v_txt VARCHAR2(100);
3 BEGIN
4 v_txt := ltrim(regexp_substr('HERE IS AN ASCII CHARACTER', 'IS AN [[:alnum:]]*'),'IS AN ');
5 DBMS_OUTPUT.PUT_LINE('Word after IS AN: '||v_txt);
6 END;
7 /
Word after IS AN: CII
PL/SQL procedure successfully completed
SQL>
SQL> DECLARE
2 v_txt VARCHAR2(100);
3 BEGIN
4 v_txt := regexp_replace('HERE IS AN ASCII CHARACTER', 'IS AN ([[:alnum:]]*)|.','\1');
5 DBMS_OUTPUT.PUT_LINE('Word after IS AN: '||v_txt);
6 END;
7 /
Word after IS AN: ASCII
PL/SQL procedure successfully completed
SQL> -----------
VB
http://volder-notes.blogspot.com/ -
Can somebody help me in getting some good material for Regular Expressions and IP Community list
can somebody help me in getting some good material for Regular Expressions and IP Community list
I'm not sure what you mean by "IP Community list", but here are 3 reference sites for Regular Expressions:
Regular Expression Tutorial - Learn How to Use Regular Expressions
http://www.regular-expressions.info/tutorial.html
Regular Expressions Cheat Sheet by DaveChild
http://www.cheatography.com/davechild/cheat-sheets/regular-expressions/
Regular Expressions Quick Reference
http://www.autohotkey.com/docs/misc/RegEx-QuickRef.htm -
Hello,
I have an XML file containing regular expressions and i parse the file, extract the pattern from it and search for it using java regex package. The problem is it works fine when patterns are words but when the pattern is something like
write \\d+ (write followed by a space followed by one or mre digits) it doesn't work.
I wrote the same code but with the pattern embedded in it,ie. without using XML and it worked. But when extracting with XML it fails.
Also if the pattern is write[0-9] it only extracts write[0-9 and gives an error of no closing bracket.
Could anyone please tell me what i am missing out
Thank youthank you for your replies. Well i have still no got over the problem so i am posting my code here and hoping it can get solved
import org.xml.sax.*;
import org.xml.sax.helpers.*;
import java.io.*;
import java.util.regex.*;
class textextractor extends DefaultHandler{
boolean regex=false;
public void startElement(String namespaceURI,String localName,String qn,Attributes attr)
if(localName.equals("REGEX"))
regex=true;
public void characters(char [] text,int start,int length)throws SAXException {
String t=new String(text,start,length);
boolean flag=false;
if(regex==true)
Pattern pattern;
String w=new String(t);
pattern = Pattern.compile(w);
Matcher matcher;
matcher=pattern.matcher("there is a bat read write 13 error at line ");
while(matcher.find())
flag=true;
System.out.println("I found the text \"" + matcher.group() +"\" starting at index "
+ matcher.start() +"and ending at index " + matcher.end() + ".");
if(!flag)
System.out.println("not found");
regex=false;
public class saxt2 {
public static void main(String args[]) {
try {
XMLReader parser= XMLReaderFactory.createXMLReader();
ContentHandler handler=new textextractor();
parser.setContentHandler(handler);
parser.parse("d:\\regex.xml");
}catch (Exception e) {
System.err.println(e);
}The xml file is
<RegularExpression>
<REGEX>write</REGEX>
<REGEX>write \\d+</REGEX>
<REGEX>read[0-9]</REGEX>
</RegularExpression>by running the code you can see that write is found,write \\d+ doesn't match write 13 in the string and read[0-9] gives and error.
Any help will be greatly appreciated -
Find text using regular expression and add highlight annotation
Hi Friends
Is it possible to find text using regular expression and add highlight annotation using pluginA plugin can use the PDWordFinder to get a list of the words on a page, and their location. That's all that the API offers for searching. Of course, you can use a regular expression library to work with that word list.
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Regular expression and output format
hi all,
i have following scenario-
regular expression: [0-9]{3}-[0-9]{3}-[0-9]{4}
generated value by the above regular expression: 123-234-6789
output format to display the generated above value: xxx-xxx-$1
now i need to display the generated value (123-234-6789) in the specified output format (xxx-xxx-$1) and the final output will be xxx-xxx-6789
how is it possible?
Note: here regular expression and output format can vary
br,
basharHi, Bashar
You can solve this problem by using the Data Masking Technique.
Masking data means replacing certain fields with a Mask character (such as an X). This effectively disguises the data content while preserving the same formatting on front end screens and reports. For example, a column of credit card numbers might look like:
4346 6454 0020 5379
4493 9238 7315 5787
4297 8296 7496 8724
and after the masking operation the information would appear as:
4346 XXXX XXXX 5379
4493 XXXX XXXX 5787
4297 XXXX XXXX 8724
The masking characters effectively remove much of the sensitive content from the record while still preserving the look and feel. Take care to ensure that enough of the data is masked to preserve security.
It would not be hard to regenerate the original credit card number from a masking operation such as: 4297 8296 7496 87XX since the numbers are generated with a specific and well known checksum algorithm.
Best Regards,
Mahfuz Khan -
Assistance with Regular Expression and Tcl
Assistance with Regular Expression and Tcl
Hello Everyone,
I recently began learning Tcl to develop scripts for automating network switch deployments.
In my script, I want to name the device with a location and the last three octets of the base mac address.
I can get the Base MAC address by :
show version | include Base
Base ethernet MAC Address : 00:00:00:DB:CE:00
And I can get the last three octets of the MAC address using the following regular expression.
([0-9a-f]{2}[:-]){2}([0-9a-f]{2}$)
But I have not been able to figure out how to call the regular expression in the tcl script.
I have checked several resources but have not been able to figure it out. Suggestions?
Ultimately, I want to set the last three octets to a variable (something like below) and then call the variable when I name the switch.
set mac [exec "sh version | i Base"] (include the regular expression)
ios_config "hostname location$mac"
Thanks for any assistance in advance.
ChrisThis worked for me.
Switch_1(tcl)#set result [exec show ver | inc Base]
Base ethernet MAC Address : 00:1B:D4:F8:B1:80
Switch_1(tcl)#regexp {([0-9A-F:]{8}\r)} $result -> mac
1
Switch_1(tcl)#puts $mac
F8:B1:80
Switch_1(tcl)#ios_config "hostname location$mac"
%Warning! Hostname should contain at least one alphabet or '-' or '_' character
locationF8:B1:80(tcl)# -
Regular expressions and limiting matched input
Hi everyone :) I am trying to put together a regular expression that matches strings that contain elements of the form;
{<some text>}
However, each piece of text may contain multiple embedded instances of this pattern. I want to ensure that I am always getting the first (or outermost) instance.
So, if I had;
{OneStart}{TwoStart}{TwoEnd}{OneEnd}
I want to make sure that I get 'One' first and 'Two' second. So I have to place a stipulation in my regular expression to match this pattern only if it has not located the patten previously.
At the moment, I have this -
([^\\{]*?)(\\{TagStart\\})(.*?)(\\{TagEnd\\})(.*)
What I think that I have to do is modify the first capture group '([^\\{]*?)' which at the moment only does not match if a preceding '{' is found to match only if a preceding '{<text>}' sequence is not found.
Anyone got any idea how to do this?
Thanks in advance.
BenDoesn't it work anyway, since you're using greedy operators? If not, won't it work if you remove the .* at the end and use find() rather than matches()? And finally, what's the (.*?) supposed to match? Looks to me like that should be .*
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Regular expressions and capture groups
Hi everyone :)
Is there a way to override the default behaviour of capture groups in regular expressions? More specifically I want to override this:
"The captured input associated with a group is always the subsequence that the group most recently matched."
For example, if I have a string that is this:
* <comment one>
* <comment two>
<some text>
I have a pattern of the form "(.*)(/\\*.*\\*/)(.*)" which will match multi-line comments. I have also specified the flag DOTALL so that the predefined character class '.' matches over line-breaks.
If I apply this pattern to the above string I get comment two being captured, not comment one. This is because of the stipulation that I cited above.
I need to be able to capture only the first match, and prevent the capture group from being overwritten by more recent matches.
Is this possible? Any ideas?
Thanks in advance.
Kind regards,
Ben DeanyIs there a way to override the default behaviour of
capture groups in regular expressions? More
specifically I want to override this:No, but you don't need to.
I have a pattern of the form "(.*)(/\\*.*\\*/)(.*)"
which will match multi-line comments.Comment two is captured by the second group because comment one is eaten by the first group. Use the reluctant quantifier "*?" on the . in the first group instead of the greedy quantifier "*" to get what is apparently the behavior you want. Then the first group will contain nothing, the second group will contain comments one and two, and the third group will contain the following text.
.* is a very powerful thing to use. It will match everything in its path, guzzling text like moonshine at Mardi Gras. The only reason it doesn't match comment two as well is because then the expression as a whole would not match.
The parentheses surrounding the first and third groups are not needed (unless you want to use group methods on them too). -
Regular Expressions and Collections
Is it possible to use refular expressions when validating collection items?
I have a loop that checks collection values for null, not null etc. I would also like to validate the format of some text fields in the same collection loop.
i.e.
for i in 1..htmldb_application.g_f02.count
loop
if
replace(htmldb_application.g_f07(i), 'NULL',NULL) is null
and TO_NUMBER(NVL(htmldb_application.g_f02(i), 0)) > 0
THEN
return 'A Demand Quantity Value Must Be Specified.';
elsif
-- check htmldb_application.g_f07(i) is correctly formatted using Reg Expressions
then
return 'Reg Expression error text goes here';
end if;
end loop;
Regards
DuncanWell, the obvious answer is "only write the data to the database if the input doesn't match the regular expression."
Presumably you're really asking how to do that - but it depends upon how your application is structured in the first place, and you haven't told us anything at all about that. -
Whats the different between regular strems and buffered streams?
Hum , Hey.
Whats the different between regular streams(un buffered) and buffered streams?
When should I use buffered streams and when should I use buffered streams?
Thanks in advance !Gonen wrote:
CeciNEstPasUnProgrammeur wrote:
Heck, I often asked myself that, too. If only there were any documentation for those classes one could read...
The buffer allows the stream to read a whole chunk of data, even though your program requests it one byte at a time. Reading larger chunks from a file e.g. is much faster than trying to read single bytes. Especially considering that usually, a whole cluster is read and you'd discard all but one byte, and then repeat the same...so if the buffered is faster . why there is un buffered streams?Lots of reasons. Maybe you're sure you're going to send or receive all the data in one transaction, so you don't want to waste memory on another buffer. Maybe you're sending data to a device that requires real-time input, like a robotic arm.
Maybe you are looking for
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Fonts in Safari & Chrome are outlined
http://imgur.com/Jobwo Message was edited by: William Chamberlin