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Reference - What does this regex mean?
(1 answer)
Closed 2 years ago.
I have some string with such format:
aaaaaaaaaaaa //first line
[key = [metadata = 1 metadata = 2 metadata =3] KEY(1) = 100
KEY(2) = 16:30:00 KEY(3) = 2020-12-12 08:30:30 KEY(4) = 0]
I want to get the key value pairs in Json format like
{"KEY(1)":"100", "KEY(2)":"16:30:00", "KEY(3)":"2020-12-12 08:30:30", "KEY(4)":"0"}
I am kind of struggling to deal with the last part, because there could be space also in value like 2020-12-12 08:30:30, so the only way I can think of is to find the "=", the data between the first space and the second space on the left is the current key, and all rest util the previous "=" is the value for previous key, which is tricky and I am new to REGEX, how should I do it? Thanks!
I would not try to use a regex to do this.
There are difficulties you haven't considered yet. For example, the quoted string can contain an =, or (worse) it can contain a quote mark, so something like this is unusual, but seems to be legitimate:
{ "\"key\"=\"value\"" = "This is the value"}
When you're done parsing it, the key in this case will be "key" = "value" (with the quote marks and equal sign included in the string.
So not only do you need to recognize the beginning and end of each part of what you're dealing with, but in some cases you need to do some transformations on it to get the correct string.
Now, I'm not going to say this can't be done using a regex--but I think (at best) developing a regex that will work correctly will be more trouble than it's worth.
Related
I want to accomplish the following with ruby and if possible a regex:
Input: "something {\"key\":\"value\",\"key2\":3}"
Output: [["\"key\"", "\"value\""], [["\"key2\"", "3"]]
My attempt so far:
s = "something {key:\"value\",key2:3}"
s.scan(/.* {(?:([^:]+):([^,}]+),?)+}$/)
# Output: [["\"key2\"", "3"]]
For some reason the regex above only matches the last key value pair. Does someone know how to retrieve all the pairs?
Just to be clear, "something" can be any kind of string. For this reason, solutions such as (1) splitting the text directly on the equal or (2) a regex as used in s.scan(/(?:([^:]+):([^,}]+),?)/) don't work for me.
I know there are similar questions on SO. Still, from what I saw, they mostly tend towards the solutions 1 & 2 or focus on a single key value pair.
your string looks like a json data structure encoded as a string, you can use JSON.parse for this as long as you remove the word "something " from the string
require 'json'
string = "something {\"key\":\"value\",\"key2\":3}"
# the following line removes the word something
string = string[string.index("{")..-1]
x = JSON.parse(string)
puts x["key"]
puts x["key2"]
you can then convert that to an array if required
alternatively if you want to use regular expressions try
string.scan(/(?:"(\w+)":"?(\w+)"?)/)
This question already has an answer here:
Parse parameters and values of smarty-like string in PHP
(1 answer)
Closed 2 years ago.
Question, basically
If I have a regex ((key1)(value1)|(key2)(value2)), key1 is ref'd by $2 & key2 by $4. Is it possible to combine these into the same reference? (I'm guessing no)
Thus $7 might be key & $8 might be value, regardless of which capture group it originated in
Any regex masters who can solve the below? I've spent a couple hours on it and am kinda stuck.
I would like it to work across different regex engines with minimal modifications. Been testing with PCRE on regexr.com
What I'm doing
I'm trying to make a file format that is parsed into key/value pairs with a single regex.
There's just a few rules:
Keys are a string of characters at the start of a line, followed by a colon (:).
So far, I'm just using [a-z]+ for the keys, but that will be expanded to some more characters. I don't think that will functionally change the regex.
values can be multi-line
all white-space is trimmed from values
I don't think I've added this to the regex yet
Values end when another key begins
delimiters can be used to wrap values in the format key:DELIM: then the value, then :DELIM: on it's own line.
Delimiter can be an empty string, thus :: serves as a delimiter
The regex I have
Correctly matches non-delimited keys & values
([a-z]+):((?:(?:.|\n|\r)(?!^[a-z]+:))+)
Correctly matches delimited keys & values
([a-z]+):([A-Z]*:)((.|\r|\n)*)^:\2
Matches everything correctly, BUT requires two sets of references
(?:(?:([a-z]+):([A-Z]*:)((.|\r|\n)*)^:\2)|([a-z]+):((?:(?:.|\n|\r)(?!^[a-z]+:))+))
$1 & $5 are keys. $3 & $6 are values
Sample Input
key: value 1
nightmare:DELIM:
notakey:
obviously not a key
notakey:
:DELIM:
abc: value 2
new line
anotherkey:: value
nostring: on this one
::
Which would yield These key/value pairs
key
value1
nightmare
notakey:
obviously not a key
notakey:
abc
value 2
new line
anotherkey
value
nostring: on this one
My latest attempt
My latest attempt got me here, but it doesn't actually match anything:
^([a-z]+): # key CP#1
((?:[A-Z]*:)? # delimiter, optional
(?:\s*(\r?\n|$)) # whitespace, new line OR end of file (line?)
) # CP#2
( # value, CP#3
(?:(?:
(?:.|\n|\r) # characters we want
(?!^[a-z]+:) # But NOT if those characters make up a key
)+)
| # or
((.|\r|\n)*) # characters we want
^:\2 # Ends with delimiter
) # delimited value
Thanks to the commenter for the ?| operator, which turns out to be what I needed.
((key1)(value1)|(key2)(value2)) => (?|(key1)(value1)|(key2)(value2)).
(?|(?:([a-z]+):([A-Z]*:)((.|\r|\n)*)^:\2)|([a-z]+):()((?:(?:.|\n|\r)(?!^[a-z]+:))+)) basically does it, though the final product certainly still needs more work.
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My regex is matching too much. How do I make it stop? [duplicate]
(5 answers)
Closed 6 years ago.
I'm trying to write a regex for the following pattern:
[MyLiteralString][0 or more characters without restriction][at least 1 digit]
I thought this should do it:
(theColumnName)[\s\S]*[\d]+
As it looks for the literal string theColumnName, followed by any number of characters (whitespace or otherwise), and then at least one digit. But this matches more than I want, as you can see here:
https://www.regex101.com/r/HBsst1/1
(EDIT) Second set of more complex data - https://www.regex101.com/r/h7PCv7/1
Using the sample data in that link, I want the regex to identify the two occurrences of theColumnName] VARCHAR(10) and nothing more.
I have 300+ sql scripts which containing create statements for every type of database object: procedures, tables, triggers, indexes, functions -- everything. Because of that, I can't be too strict with my regex.
A stored procedure's file might include text like LEFT(theColumnName, 10) which I want to identify.
A create table statement would be like theColumnName VARCHAR(12).
So it needs to be very flexible as the number(s) isn't always the same. Sometimes it's 10, sometimes it's 12, sometimes it's 51 -- all kinds of different numbers.
Basically, I'm looking for the regex equivalent of this C# code:
//Get file data
string[] lines = File.ReadAllLines(filePath);
//Let's assume the first line contains 'theColumnName'
int theColumnNameIndex = lines[0].IndexOf("theColumnName");
if (theColumnNameIndex >= 0)
{
//Get the text proceeding 'theColumnName'
string temp = lines[0].Remove(0, theColumnNameIndex + "theColumnNameIndex".Length;
//Iterate over our substring
foreach (char c in temp)
{
if (Char.IsDigit(c))
//do a thing
}
}
(theColumnName).*?[\d]+
That'll make it stop capturing after the first number it sees.
The difference between * and *? is about greediness vs. laziness. .*\d for example would match abcd12ad4 in abcd12ad4, whereas .*?\d would have its first match as abcd1. Check out this page for more info.
Btw, if you don't want to match newlines, use a . (period) instead of [\s\S]
EDIT: I should note that I want a general case for any hex array, not just the google one I provided.
EDIT BACKGROUND: Background is networking: I'm parsing a DNS packet and trying to get its QNAME. I'm taking in the whole packet as a string, and every character represents a byte. Apparently this problem looks like a Pascal string problem, and using the struct module seems like the way to go.
I have a char array in Python 2.7 which includes octal values. For example, let's say I have an array
DNS = "\03www\06google\03com\0"
I want to get:
www.google.com
What's an efficient way to do this? My first thought would be iterating through the DNS char array and adding chars to my new array answer. Every time i see a '\' char, I would ignore the '\' and two chars after it. Is there a way to get the resulting www.google.com without using a new array?
my disgusting implementation (my answer is an array of chars, which is not what i want, i want just the string www.google.com:
DNS = "\\03www\\06google\\03com\\0"
answer = []
i = 0
while i < len(DNS):
if DNS[i] == '\\' and DNS[i+1] != 0:
i += 3
elif DNS[i] == '\\' and DNS[i+1] == 0:
break
else:
answer.append(DNS[i])
i += 1
Now that you've explained your real problem, none of the answers you've gotten so far will work. Why? Because they're all ways to remove sequences like \03 from a string. But you don't have sequences like \03, you have single control characters.
You could, of course, do something similar, just replacing any control character with a dot.
But what you're really trying to do is not replace control characters with dots, but parse DNS packets.
DNS is defined by RFC 1035. The QNAME in a DNS packet is:
a domain name represented as a sequence of labels, where each label consists of a length octet followed by that number of octets. The domain name terminates with the zero length octet for the null label of the root. Note that this field may be an odd number of octets; no padding is used.
So, let's parse that. If you understand how "labels consisting of "a length octet followed by that number of octets" relates to "Pascal strings", there's a quicker way. Also, you could write this more cleanly and less verbosely as a generator. But let's do it the dead-simple way:
def parse_qname(packet):
components = []
offset = 0
while True:
length, = struct.unpack_from('B', packet, offset)
offset += 1
if not length:
break
component = struct.unpack_from('{}s'.format(length), packet, offset)
offset += length
components.append(component)
return components, offset
import re
DNS = "\\03www\\06google\\03com\\0"
m = re.sub("\\\\([0-9,a-f]){2}", "", DNS)
print(m)
Maybe something like this?
#!/usr/bin/python3
import re
def convert(adorned_hostname):
result1 = re.sub(r'^\\03', '', adorned_hostname )
result2 = re.sub(r'\\0[36]', '.', result1)
result3 = re.sub(r'\\0$', '', result2)
return result3
def main():
adorned_hostname = r"\03www\06google\03com\0"
expected_result = 'www.google.com'
actual_result = convert(adorned_hostname)
print(actual_result, expected_result)
assert actual_result == expected_result
main()
For the question as originally asked, replacing the backslash-hex sequences in strings like "\\03www\\06google\\03com\\0" with dots…
If you want to do this with a regular expression:
\\ matches a backslash.
[0-9A-Fa-f] matches any hex digit.
[0-9A-Fa-f]+ matches one or more hex digits.
\\[0-9A-Fa-f]+ matches a backslash followed by one or more hex digits.
You want to find each such sequence, and replace it with a dot, right? If you look through the re docs, you'll find a function called sub which is used for replacing a pattern with a replacement string:
re.sub(r'\\[0-9A-Fa-f]+', '.', DNS)
I suspect these may actually be octal, not hex, in which case you want [0-7] rather than [0-9A-Fa-f], but nothing else would change.
A different way to do this is to recognize that these are valid Python escape sequences. And, if we unescape them back to where they came from (e.g., with DNS.decode('string_escape')), this turns into a sequence of length-prefixed (aka "Pascal") strings, a standard format that you can parse in any number of ways, including the stdlib struct module. This has the advantage of validating the data as you read it, and not being thrown off by any false positives that could show up if one of the string components, say, had a backslash in the middle of it.
Of course that's presuming more about the data. It seems likely that the real meaning of this is "a sequence of length-prefixed strings, concatenated, then backslash-escaped", in which case you should parse it as such. But it could be just a coincidence that it looks like that, in which case it would be a very bad idea to parse it as such.
So I am trying to parse through a file which has multiple "footers" (the file is an output that was designed for printing which my company wants to keep electronically stored...each footer is a new page and the new page is no longer needed as).
I am trying to look for and remove lines that look like:
1 of 2122 PRINTED 07/01/2013 04:46 Page : 1 of 11
2 of 2122 PRINTED 07/01/2013 04:46 Page: 2 of 11
3 of 2122 PRINTED 07/01/2013 04:46 Page: 3 of 11
and so on
I then want to replace the final line (which would read something like "2122 of 2122") with a "custom" footer.
I am using RegEx, but am very new to using it so how should my RegEx look in order to accomplish this? I plan on using the RegEx "count" function to find out when I've found the last line and then do a .replace on it.
I am using VB .NET, but can translate C# if required. How can I accomplish what I'm looking to do? Specifically I only care about matching/removing of a match so long as the # of matches > 1.
Here's one I created with RegExr:
/^(\d+\s+of\s+\d+)(?=\s+printed)/gim
It matches (number)(space)('of')(space)(number) at the beginning of a line, and only if it is followed by (space)('printed'), case insensitive. The /m flag turns ^ and $ into line-aware boundaries.
This is how I ended up doing it...
Private Function FixFooters(ByVal fileInput As String, Optional ByVal numberToLeaveAlone As Integer = 1) As String
Dim matchpattern As String = "^\d+\W+of\W+\d+\W+PRINTED.*$"
Dim myRegEx As New Regex(matchpattern, RegexOptions.IgnoreCase Or RegexOptions.Multiline)
Dim replacementstring As String = String.Empty
Dim matchCounter As Integer = myRegEx.Matches(fileInput).Count
If numberToLeaveAlone > matchCounter Then numberToLeaveAlone = matchCounter
Return myRegEx.Replace(fileInput, replacementstring, matchCounter - numberToLeaveAlone, 0)
End Function
I used myregextester.com to get the inital matchpattern. Since I wanted to leave the last footer alone (to manipulate it further later on) I created the numberToLeaveAlone variable to ensure we don't remove ALL of the variables. For the purposes of this program I made the default value 1, but that could be changed to zero (I only did it for readability in the calling code as I know I will ALWAYS want to leave one...but I do like to reuse code). It's fairly fast, I'm sure there are better ways out there, but this one made the most sense to me.