I am looking for a pattern to match if a special character was used within a GET variable, for example, in this case, if the character '<' was used by a user at somepoint in the variable 'x'. Currently, I've created the following regex pattern:
^example\.php\?(.*)x=(.*)<(.*)&
So, for example, the following strings would be matched:
example.php?x=abc"def&y=ghi
example.php?x=abcde"f&y=ghi
But with the pattern that I'm currently using, every other GET variable that might be using "<" is also being matched, for example:
example.php?x=abcdef&y=ghi"&z=klm
How should I overcome this so that it matches everything up to the first appeareance of the '&' character (so that it only analyses the 'x' variable)?
I don't know if the question is understandable, if not, I'll try to provide further details.
It took me sometime but I finally discovered what should I do.
I couldn't parse the url and get the value for X because the regex is going to be on a SQL query (As far as I'm aware, that's no easy task).
The answer would be something in the light of:
example\.php\?(.*)x=[^&]*<
I hope that I can help someone
Related
I'm trying to see if its possible to extend an existing arbitrary regex by prepending or appending another regex to match within matches.
Take the following example:
The original regex is cat|car|bat so matching output is
cat
car
bat
I want to add to this regex and output only matches that start with 'ca',
cat
car
I specifically don't want to interpret a whole regex, which could be quite a long operation and then change its internal content to match produce the output as in:
^ca[tr]
or run the original regex and then the second one over the results. I'm taking the original regex as an argument in python but want to 'prefilter' the matches by adding the additional code.
This is probably a slight abuse of regex, but I'm still interested if it's possible. I have tried what I know of subgroups and the following examples but they're not giving me what I need.
Things I've tried:
^ca(cat|car|bat)
(?<=ca(cat|car|bat))
(?<=^ca(cat|car|bat))
It may not be possible but I'm interested in what any regex gurus think. I'm also interested if there is some way of doing this positionally if the length of the initial output is known.
A slightly more realistic example of the inital query might be [a-z]{4} but if I create (?<=^ca([a-z]{4})) it matches against 6 letter strings starting with ca, not 4 letter.
Thanks for any solutions and/or opinions on it.
EDIT: See solution including #Nick's contribution below. The tool I was testing this with (exrex) seems to have a slight bug that, following the examples given, would create matches 6 characters long.
You were not far off with what you tried, only you don't need a lookbehind, but rather a lookahead assertion, and a parenthesis was misplaced. The right thing is: Put the original pattern in parentheses, and prepend (?=ca):
(?=ca)(cat|car|bat)
(?=ca)([a-z]{4})
In the second example (without | alternative), the parentheses around the original pattern wouldn't be required.
Ok, thanks to #Armali I've come to the conclusion that (?=ca)(^[a-z]{4}$) works (see https://regexr.com/3f4vo). However, I'm trying this with the great exrex tool to attempt to produce matching strings, and it's producing matches that are 6 characters long rather than 4. This may be a limitation of exrex rather than the regex, which seems to work in other cases.
See #Nick's comment.
I've also raised an issue on the exrex GitHub for this.
Given this string: hello"C07","73" (quotes included) I want to get "C07". I'm using (?:hello)|(?<=")(?<screen>[a-zA-Z0-9]+)?(?=") to try to do this. However, it consistently matches "73" as well. I've tried ...0-9]+){1}..., but that doesn't work either. I must be misunderstanding how this is supposed to work, but I can't figure out any other way.
How can I get just the first set of characters between quotes?
EDIT: Here's a link to show my problem.
EDIT: Ok, here's exactly what I'm trying to do:
Basically, what I'm trying to get is this: 1) a positive match on "hello", 2) a group named "screen" with, in this case, "C07" in it and 3) a group named "format" with, in this case, "73" in it.
Both the "C07" and "73" will vary. "hello" will always be the same. There may or may not be an extra comma between "hello" and the first double-quote.
For you initial question of how to stop after the first match either removing the global search, or searching from the start of the string would accomplish that.
For the latter question you can name your groups and just keep extending the pattern throughout the line(s).
hello"(?<screen>[^"]+)","(?<format>[^"]+)"
Demo: http://regex101.com/r/PBXe8l/1
Based on your regex example, why not:
^(?:hello)"([a-zA-Z\d]+)"
Regex Demo
I have this regex for email validation (assume only x#y.com, abc#defghi.org, something#anotherhting.edu are valid)
/^[a-zA-Z0-9]+#[a-zA-Z0-9]\.(com)|(edu)|(org)$/i
But #abc.edu and abc#xyz.eduorg are both valid as to the regex above. Can anyone explain why that is?
My approach:
there should be at least one character or number before #
then there comes #
there should be at least one character or number after # and before .
the string should end with either edu, com, or org.
Try this
/^[a-zA-Z0-9]+#[a-zA-Z0-9]+\.(com|edu|org)$/i
and it should become clear - you need to group those alternatives, otherwise you can match any string that has 'edu' in it, or any string that ends with org. To put it another way, your version matches any of these patterns
^[a-zA-Z0-9]+#[a-zA-Z0-9]\.(com)
(edu)
(org)$
It's worth pointing out that the original poster is using this as a regex learning exercise. This would be a terrible regex for actual production use! It's a thorny problem - see Using a regular expression to validate an email address for a lot more depth.
Your grouping parentheses are incorrect:
/^[a-zA-Z0-9]+#[a-zA-Z0-9]+\.(com|edu|org)$/i
Can also just use one case as you're using the i modifier:
/^[a-z0-9]+#[a-z0-9]+\.(com|edu|org)$/i
N.B. you were also missing a + from the second set, I assume this was just a typo...
What you have written is the equivalent of matching something that:
Begins with [a-zA-Z0-9]+#[a-zA-Z0-9].com
contains edu
or ends with org
What you were looking for was:
/^[a-z0-9]+#[a-z0-9]+\.(com|edu|org)$/i
Your regex looks ok.
I guess you are looking using a find function in stead of a match function
Without specifying what you use it is a bit difficult, but in Python you would write
import re
pattern = re.compile ('^[a-zA-Z0-9]+#[a-zA-Z0-9]\.(com)|(edu)|(org)$')
re.match('#abc.edu') # fails, use this to validate an input
re.search('#abc.edu') # matches, finds the edu
Try to use it:
[a-zA-Z0-9]+#[a-zA-Z0-9]+.(com|edu|org)+$
U forget about + modificator if u want to catch any combinations of (com|edu|org)
Upd: as i see second [a-zA-Z0-9] u missed + too
For reference, this is the regex tester I am using:
http://www.rsyslog.com/regex/
How can I modify this regular expression:
[^;]+
to receive multiple sub-matches for the following test string:
;first;second;third;fourth;fifth and sixth;seventh;
I currently only receive one sub-match:
first
Basically I want each sub-match to consist of the content between ; characters, I am hoping for a sub-match list like this:
first
second
third
fourth
fifth and sixth
seventh
Following information given in the comments I discovered that the reason I can't get more than one sub-match is that I need to specify the global modifier - and I can't seem to figure out how to do that in the ryslog regex tester I am using.
However, this did lead me to solve my problem in a slightly different manner. I came up with this regular expression which still only gives one match, but the number near the end acts as the index for the desired match, so for example:
(?:;([^;]+)){5}
matches this from my test string in the question:
fifth and sixth
While this solution allows me to achieve what I wanted - though in a different manner - the true answer to my question is found in HamZa's comments. More specifically:
How can I modify the regular expression to receive multiple
sub-matches?
The answer is, you can't modify the regular expression itself in order to get multiple sub-matches. Setting the global modifier is required in order to do that.
Based on this information I have posted a new question on serverfault targeted specifically to the rsyslog regular expression system.
I am trying to use PSQL, specifically AWS Redshift to parse a line. Sample data follows
{"c.1.mcc":"250","appId":"sx-calllog","b.level":59,"c.1.mnc":"01"}
{"appId":"sx-voice-call","b.level":76,"foreground":9}
I am trying the following regex in order to to extract the appId field, but my query is returning empty fields.
'appId\":\"[\w*]\",'
Query
SELECT app_params,
regexp_substr(app_params, 'appId\":\"[\w*]\",')
FROM sample;
You can do that as follows:
(\"appId\":\"[^"]*\")(?:,)
Demo: http://regex101.com/r/xP0hW3
The first extracted group is what you want.
Your regex was not matching because \w does not match -
Adding this here despite this being an old question since it may help someone viewing this down the road...
If your lines of data are valid json, you can use Redshift's JSON_EXTRACT_PATH_TEXT function to extract the value a given key. Emphasis on the json being valid, as it will fail if even one line cannot be parsed and Redshift will throw a JSON parsing error.
Example using given data:
select json_extract_path_text('{"c.1.mcc":"250","appId":"sx-calllog","b.level":59,"c.1.mnc":"01"}','appId');
returns sx-calllog
This is especially useful since Redshift does not support lookahead/lookbehind (it is POSIX regex) & extract groups.
You can try using some lookahead and look behinds to isolate just the text inside the quotes for the appid. (?<=appId\":\")(?=.*\",)[^\"]*. I tested this out a bit using your examples you provided here.
To explain the regex a bit more: (?<=appId\":\")(?=.*\",)[^\"]*
(?<=appId\":\"): positive look behind for appid":". Since you don't want the appid text itself being returned (just the value), you can preface the regex with a look behind to say "find me the following regex, but only when it is following the look behind text.
(?=.*\",): positive look ahead for the ending ",. You don't want quotes to be returned in your match, but as with number 1 you want your regex to be bounded a bit and a look ahead does that.
[^\"]*: The actual matching portion. You want to find the string of chars that are NOT ". This will match the entire value and stop matching right before the closing ".
EDIT: Changed the 3rd step a little bit, removed the , from that last piece, it is not needed and would break the match if the value were to actually contain a ,.