I am trying to parse a string such as: &1 first &2 second &4 fourth \\, and from it to build a table
t = {1=first, 2=second, 4=fourth}
I'm not very experienced with regex in general so my naive try (disregarding the \\ and table parts for the moment) was
local s = [[&1 first &2 second &4 fourth \\]]
for k,v in string.gmatch(s, "&(%d+)(.-)&") do
print("k = "..k..", v = "..v)
end
which gives only the first captured pair when I was expecting to see two captured pairs. I've done some reading and found the lpeg library, but it's massively unfamiliar to me. Is lpeg needed here? Could anyone explain my error?
&(%d+)(.-)& matches &1 first &
Leaving 2 second &4 fourth \\ to be matched on
Your pattern does not match any further items
If you know that the values are one word, this should work:
string.gmatch(s, "&(%d+)%s+([^%s&]+)")
Take "&", followed by 1 or more digits (captured), followed by one or more space and then one or more non-space, non-& characters (captured).
Related
I'm (again) stuck because patterns... so let's see if with a little of help... The case is I have e. g. a string returned by a function that contains the following:
📄 My Script
ScriptID:RL_SimpleTest
Version:0.0.1
ScriptType:MenuScript
AnotherKey:AnotherValue
And, maybe, some more text...
And I'd want to parse it line by line and should the line contains a ":" get the left side content of the line in a variable (k) and the right content in another one (v), so e. g. I'd have k containing "ScriptID" and v containing "RL_SimpleTest" for the second line (the first one should be just ignored) and so on...
Well, I've started with something like this:
function RL_Test:StringToKeyValue(str, sep1, sep2)
sep1 = sep1 or "\n"
sep2 = sep2 or ":"
local t = {}
for line in string.gmatch(str, "([^" .. sep1 .. "]+)") do
print(line)
for k in string.gmatch(line, "([^" .. sep2 .. "]+)") do --Here is where I'm lost trying to get the key/value pair separately and at the same time...
--t[k] = v
print(k)
end
end
return t
end
With the hope once I got isolated the line containing the data in the key:value form that I want to extract, I'd be able to do some kind of for k, v in string.gmatch(line, "([^" .. sep2 .. "]+)") or something so and that way get the two pieces of data, but of course it doesn't work and even though I have a feeling it's a triviality I don't know even where to start, always for the lack of patterns understanding...
Well, I hope at least I exposed it right... Thanks in advance for any help.
local t = {}
for line in (s..'\n'):gmatch("(.-)\r?\n") do
for a, b in line:gmatch("([^:]+):([^:\n\r]+)") do
t[a] = b
end
end
The pattern is quite simple. Match anything that is not a colon that is followed by a colon that is followed by anything that is not a colon or a line break. Put what you want in captures and you're done.
I assume every line is of the format k:v, containing exactly one colon, or containing no colon (no k/v pair).
Then you can simply first match nonempty lines using [^\n]+ (assuming UNIX LF line endings), then match each line using ^([^:]+):([^:]+)$. Breakdown of the second pattern:
^ and $ are anchors. They force the pattern to match the entire line.
([^:]+) matches & captures one or more non-semicolon characters.
This leaves you with:
function RL_Test:StringToKeyValue(str)
local t = {}
for line in str:gmatch"[^\n]+" do
local k, v = line:match"^([^:]+):([^:]+)$"
if k then -- line is k:v pair?
t[k] = v
end
end
return t
end
If you want to support Windows CRLF line endings, use for line in (s..'\n'):gmatch'(.-)\r?\n' do as in Piglet's answer for matching the lines instead.
This answer differs from Piglet's answer in that it uses match instead of gmatch for matching the k/v pairs, allowing exactly one k/v pair with exactly one colon per line, whereas Piglet's code may extract multiple k/v pairs per line.
I need to encapsulate in some way pattern in lua pattern matching to find whole sequence of this pattern in string. What do I mean by that.
For example we have string like that:
"word1,word2,word3,,word4,word5,word6, word7,"
I need to match first sequence of words followed by coma (word1,word2,word3,)
In python I would use this pattern "(\w+,)+", but similar pattern in lua (like (%w+,)+), will return just nil, because brackets in lua patterns means completely different thing.
I hope now you see my problem.
Is there a way to do repeating patterns in lua?
Your example wasn't too clear in terms of what should happen to the word4,word5,word6 and word7,
This would give you any seqence of comma separated words without white space or empty positions.
local text = "word1,word2,word3,,word4,word5,word6, word7,"
-- replace any comma followed by any white space or comma
--- by a comma and a single white space
text = text:gsub(",[%s,]+", ", ")
-- then match any sequence of >=1 non-whitespace characters
for sequence in text:gmatch("%S+,") do
print(sequence)
end
Prints
word1,word2,word3,
word4,word5,word6,
word7,
You could do this easily using LPeg if that's available to you:
local lpeg = require "lpeg"
local str = "word1,word2,word3,,word4,word5,word6, word7,"
local word = (lpeg.R"az"+lpeg.R"AZ"+lpeg.R"09") ^ 1
local sequence = lpeg.C((word * ",") ^1)
print(sequence:match(str))
Currently I have code that looks like this:
somestring = "param=valueZ&456"
local stringToPrint = (somestring):gsub("(param=)[^&]+", "%1hello", 1)
StringToPrint will look like this:
param=hello&456
I have replaced all of the characters before the & with the string "hello". This is where my question becomes a little strange and specific.
I want my string to appear as: param=helloZ&456. In other words, I want to preserve the character right before the & when replacing the string valueZ with hello to make it helloZ instead. How can this be done?
I suggest:
somestring:gsub("param=[^&]*([^&])", "param=hello%1", 1)
See the Lua demo
Here, the pattern matches:
param= - literal substring param=
[^&]* - 0 or more chars other than & as many as possible
([^&]) - Group 1 capturing a symbol other than & (here, backtracking will occur, as the previous pattern grabs all such chars other than & and then the engine will take a step back and place the last char from that chunk into Group 1).
There are probably other ways to do this, but here is one:
somestring = "param=valueZ&456"
local stringToPrint = (somestring):gsub("(param=).-([^&]&)", "%1hello%2", 1)
print(stringToPrint)
The thing here is that I match the shortest string that ends with a character that is not & and a character that is &. Then I add the two ending characters to the replaced part.
I am using LUA to create a table within a table, and am running into an issue. I need to also populate the NIL values that appear, but can not seem to get it right.
String being manipulated:
PatID = '07-26-27~L73F11341687Per^^^SCI^SP~N7N558300000Acc^'
for word in PatID:gmatch("[^\~w]+") do table.insert(PatIDTable,word) end
local _, PatIDCount = string.gsub(PatID,"~","")
PatIDTableB = {}
for i=1, PatIDCount+1 do
PatIDTableB[i] = {}
end
for j=1, #PatIDTable do
for word in PatIDTable[j]:gmatch("[^\^]+") do
table.insert(PatIDTableB[j], word)
end
end
This currently produces this output:
table
[1]=table
[1]='07-26-27'
[2]=table
[1]='L73F11341687Per'
[2]='SCI'
[3]='SP'
[3]=table
[1]='N7N558300000Acc'
But I need it to produce:
table
[1]=table
[1]='07-26-27'
[2]=table
[1]='L73F11341687Per'
[2]=''
[3]=''
[4]='SCI'
[5]='SP'
[3]=table
[1]='N7N558300000Acc'
[2]=''
EDIT:
I think I may have done a bad job explaining what it is I am looking for. It is not necessarily that I want the karats to be considered "NIL" or "empty", but rather, that they signify that a new string is to be started.
They are, I guess for lack of a better explanation, position identifiers.
So, for example:
L73F11341687Per^^^SCI^SP
actually translates to:
1. L73F11341687Per
2.
3.
4. SCI
5. SP
If I were to have
L73F11341687Per^12ABC^^SCI^SP
Then the positions are:
1. L73F11341687Per
2. 12ABC
3.
4. SCI
5. SP
And in turn, the table would be:
table
[1]=table
[1]='07-26-27'
[2]=table
[1]='L73F11341687Per'
[2]='12ABC'
[3]=''
[4]='SCI'
[5]='SP'
[3]=table
[1]='N7N558300000Acc'
[2]=''
Hopefully this sheds a little more light on what I'm trying to do.
Now that we've cleared up what the question is about, here's the issue.
Your gmatch pattern will return all of the matching substrings in the given string. However, your gmatch pattern uses "+". That means "one or more", which therefore cannot match an empty string. If it encounters a ^ character, it just skips it.
But, if you just tried :gmatch("[^\^]*"), which allows empty matches, the problem is that it would effectively turn every ^ character into an empty match. Which is not what you want.
What you want is to eat the ^ at the end of a substring. But, if you try :gmatch("([^\^])\^"), you'll find that it won't return the last string. That's because the last string doesn't end with ^, so it isn't a valid match.
The closest you can get with gmatch is this pattern: "([^\^]*)\^?". This has the downside of putting an empty string at the end. However, you can just remove that easily enough, since one will always be placed there.
local s0 = '07-26-27~L73F11341687Per^^^SCI^SP~N7N558300000Acc^'
local tt = {}
for s1 in (s0..'~'):gmatch'(.-)~' do
local t = {}
for s2 in (s1..'^'):gmatch'(.-)^' do
table.insert(t, s2)
end
table.insert(tt, t)
end
I'm not quite good in regex.
With my input string LT 1 BLK 4 LAKES OF PARKWAY 5 R/P & AMEND
I'd like to match just the only part between the figure 4 and 5 in the string.
meaning that, my expected result is LAKES OF PARKWAY.
I've tried to come up with a pattern to get such result.
\d+\s+([A-z ]+)(\d+.*?)*$
but with my pattern, it only matches BLK and 5 R/P & AMEND, as group #1 and group #2 respectively. At the end of my thought pattern, I decide to use end of string matching, $.
So, when 5 R/P & AMEND got matched, the pointer should move further behind to the sub sequence part. Then, ([A-z ]+) should match LAKES OF PARKWAY.
What's wrong with my pattern? and how to get it to work?
Any advice would be very much appreciated.
Try \d+\s+(\D+)\d+\D*$
\D means 'anything that is not \d, so it won't be allowed to match, for example, between the first 1 and 4, because then the ending of the regex would be rejected at the later 5.