Probably it's an easy thing, but I'm a Lua beginner...
I'm creating a very simple QSC QSYS plugin to control a projection server using KVL API. Server API is based on hex strings.
For example this command asks the server to load a the playlist with 9bf5455689ed4c019731c6dd3c071f0e uuid:
Controls["LoadSPL"].EventHandler = function()
sock:Write(
"\x06\x0e\x2b\x34\x02\x05\x01\x0a\x0e\x10\x01\x01\x01\x03\x09\x00\x83\x00\x00\x14\x00\x00\x00\x01\x9b\xf5\x45\x56\x89\xed\x4c\x01\x97\x31\xc6\xdd\x3c\x07\x1f\x0e"
)
end
Now I need to be able to create a string with a variable UUID, according to the text indicated in a textbox (or a list of available UUIDs read from the server) in the user interface.
I will concatenate this string to the fixed part of the command.
How can I correctly make a string like
ad17fc696b49454db17d593db3e553e5 become
\xad\x17\xfc\x69\x6b\x49\x45\x4d\xb1\x7d\x59\x3d\xb3\xe5\x53\xe5?
Try this:
local input = "ad17fc696b49454db17d593db3e553e5"
local output = input:gsub("%w%w", function(s) return string.char(tonumber(s, 16)) end)
Explanation: this takes every pair of characters, interprets them as base 16 numeric string, and then takes the character with that number, and uses that to replace the original characters.
EDIT: To make it clear what's going on, and why the other answers are wrong, backslash escape sequences like \xad are a feature of the Lua source code, in memory it's represented by a byte with value 173, just like A is represented by a byte with value 65. Trying to concatenate a literal backslash character with hexadecimal characters does not create an escape code. So the way to do that is manually with string.char.
#! /usr/bin/env lua
str = 'ad17fc696b49454db17d593db3e553e5'
strx = ''
for i = 1, #str, 2 do -- loop through every-other position in your string
chars = str :sub( i, i+1 ) -- capture every 2 chars
strx = strx ..'\\x' ..chars
end -- append a literal backslash, the letter x, then those 2 chars
target = [[\xad\x17\xfc\x69\x6b\x49\x45\x4d\xb1\x7d\x59\x3d\xb3\xe5\x53\xe5]]
print( x, x == target ) -- print results, and test if it meets expected target
\xad\x17\xfc\x69\x6b\x49\x45\x4d\xb1\x7d\x59\x3d\xb3\xe5\x53\xe5 true
This can be code-golfed into a one-liner
x=''for i=1,#s,2 do x=x..'\\x'..s:sub(i,i+1)end
Related
I'm trying to take decimal number as an input and I need output of all numbers but without the point symbol in it.
Example input: 123.4
Wanted output 1234
The problem I have that when converting decimal number into string and trying to remove "." using :gsub('%.', '') its removing the point symbol but outputs 1234 1 .
I have tried :gsub('.', '') as well but it outputs 5.
I'm clueless where those numbers come from, here is the screenshot:
Use this syntax to get what you want and discard/ignore what you dont need...
local y = 123.4
-- Remove decimal point or comma here
local str, matches = tostring(y):gsub('[.,]', '')
-- str holds the first return value
-- The second return value goes to: matches
-- So output only the string...
print(str) -- Output: 1234
-- Or/And return it...
return str
There are two issues at play here:
string.gsub returns two values, the resulting string and the number of substitutions. When you pass the results of gsub to print, both will be printed. Solve this by either assigning only the first return value to a variable (more explicit) or surrounding gsub with parenthesis.
. is a pattern item that matches any character. Removing all characters will leave you with the empty string; the number of substitutions - 5 in your example - will be the number of characters. To match the literal dot, either escape it using the percent sign (%.) or enclose it within a character set ([.]), possibly adding further decimal separators ([.,] as in koyaanisqatsi's answer).
Fixed code:
local y = 123.4
local str = tostring(y):gsub("%.", "") -- discards the number of substitutions
print(str)
this is unreliable however since tostring guarantees no particular output format; it might as well emit numbers in scientific notation (which it does for very large or very small numbers), causing your code to break. A more elegant solution to the problem of shifting the number such that it becomes an integer would be to multiply the number by 10 until the fractional part becomes zero:
local y = 123.4
while y % 1 ~= 0 do y = y * 10 end
print(y) -- note: y is the number 1234 rather than the string "1234" here
how can I extract a few words separated by symbols in a string so that nothing is extracted if the symbols change?
for example I wrote this code:
function split(str)
result = {};
for match in string.gmatch(str, "[^%<%|:%,%FS:%>,%s]+" ) do
table.insert(result, match);
end
return result
end
--------------------------Example--------------------------------------------
str = "<busy|MPos:-750.222,900.853,1450.808|FS:2,10>"
my_status={}
status=split(str)
for key, value in pairs(status) do
table.insert(my_status,value)
end
print(my_status[1]) --
print(my_status[2]) --
print(my_status[3]) --
print(my_status[4]) --
print(my_status[5]) --
print(my_status[6]) --
print(my_status[7]) --
output :
busy
MPos
-750.222
900.853
1450.808
2
10
This code works fine, but if the characters and text in the str string change, the extraction is still done, which I do not want to be.
If the string change to
str = "Hello stack overFlow"
Output:
Hello
stack
over
low
nil
nil
nil
In other words, I only want to extract if the string is in this format: "<busy|MPos:-750.222,900.853,1450.808|FS:2,10>"
In lua patterns, you can use captures, which are perfect for things like this. I use something like the following:
--------------------------Example--------------------------------------------
str = "<busy|MPos:-750.222,900.853,1450.808|FS:2,10>"
local status, mpos1, mpos2, mpos3, fs1, fs2 = string.match(str, "%<(%w+)%|MPos:(%--%d+%.%d+),(%--%d+%.%d+),(%--%d+%.%d+)%|FS:(%d+),(%d+)%>")
print(status, mpos1, mpos2, mpos3, fs1, fs2)
I use string.match, not string.gmatch here, because we don't have an arbitrary number of entries (if that is the case, you have to have a different approach). Let's break down the pattern: All captures are surrounded by parantheses () and get returned, so there are as many return values as captures. The individual captures are:
the status flag (or whatever that is): busy is a simple word, so we can use the %w character class (alphanumeric characters, maybe %a, only letters would also do). Then apply the + operator (you already know that one). The + is within the capture
the three numbers for the MPos entry each get (%--%d+%.%d+), which looks weird at first. I use % in front of any non-alphanumeric character, since it turns all magic characters (such as + into normal ones). - is a magic character, so it is required here to match a literal -, but lua allows to put that in front of any non-alphanumerical character, which I do. So the minus is optional, so the capture starts with %-- which is one or zero repetitions (- operator) of a literal - (%-). Then I just match two integers separated by a dot (%d is a digit, %. matches a literal dot). We do this three times, separated by a comma (which I don't escape since I'm sure it is not a magical character).
the last entry (FS) works practically the same as the MPos entry
all entries are separated by |, which I simply match with %|
So putting it together:
start of string: %<
status field: (%w+)
separator: %|
MPos (three numbers): MPos:(%--%d+%.%d+),(%--%d+%.%d+),(%--%d+%.%d+)
separator: %|
FS entry (two integers): FS:(%d+),(%d+)
end of string: %>
With this approach you have the data in local variables with sensible names, which you can then put into a table (for example).
If the match failes (for instance, when you use "Hello stack overFlow"), nil` is returned, which can simply be checked for (you could check any of the local variables, but it is common to check the first one.
I am trying to convert a text source into an HTML readable page.
The code I have have tried:
local newstr=string.gsub(str,"±", "±")
local newstr=string.gsub(str,"%±", "±")
However, the character shows up as  in the output.
I can't seem to find any other documentation on how to handle this specific special character. How do I handle this character when reading in so that it will output properly?
Edit: After trying suggestions I'm able to determine this:
local function sanitizeheader(str)
if not(str)then return "" end
str2 = "Depth ±"
local newstr=string.gsub(str2, string.char(177), "±")
return newstr
end
In the testing, if I use str2 ± does show up in the output. However, when I try to use str as it is passed in from reading the excel file, it doesn't pick up the character and still returns the  character.
Lua string assume strings as sequence of bytes. You are trying utf8 multi byte character. The code you are trying should work as it just replacing a sequence of bytes. However, Lua 5.3 has utf8 library to handle unicode character
local str="±®ª"
for code in str:gmatch(utf8.charpattern) do
print("&#" .. utf8.codepoint(code) .. ";")
end
Output:
±
®
ª
Check Lua Reference Manual for more info.
So I'm writing a Lua script and I tested it but I got an error that I don't know how to fix:
.\search.lua:10: malformed pattern (missing ']')
Below is my code. If you know what I did wrong, it would be very helpful if you could tell me.
weird = "--[[".."\n"
function readAll(file)
local c = io.open(file, "rb")
local j = c:read("*all")
c:close()
return(j)
end
function blockActive()
local fc = readAll("functions.lua")
if string.find(fc,weird) ~= nil then
require("blockDeactivated")
return("false")
else
return("true")
end
end
print(blockActive())
Edit: first comment had the answer. I changed
weird = "--[[".."\n" to weird = "%-%-%[%[".."\r" The \n to \r change was because it was actually supposed to be that way in the first place.
This errors because string.find uses Lua Patterns.
Most non-alpha-numeric characters, such as "[", ".", "-" etc. convey special meaning.
string.find(fc,weird), or better, fc:find(weird) is trying to parse these special characters, and erroring.
You can use these patterns to cancel out your other patterns, however.
weird = ("--[["):gsub("%W","%%%0") .. "\r?\n"
This is a little daunting, but it will hopefully make sense.
the ("--[[") is the orignal first part of your weird string, working as expected.
:gsub() is a function that replaces a pattern with another one. Once again, see Patterns.
"%W" is a pattern that matches every string that isn't a letter, a number, or an underscore.
%%%0 replaces everything that matches with itself (%0 is a string that represents everything in this match), following a %, which is escaped.
So this means that [[ will be turned into %[%[, which is how find, and similar patterns 'escape' special characters.
The reason \n is now \r?\n refers back to these patterns. This matches it if it ends with a \n, like it did before. However, if this is running on windows, a newline might look like \r\n. (You can read up on this HERE). A ? following a character, \r in this case, means it can optionally match it. So this matches both --[[\n and --[[\r\n, supporting both windows and linux.
Now, when you run your fc:find(weird), it's running fc:find("%-%-%[%[\r?\n"), which should be exactly what you want.
Hope this has helped!
Finished code if you're a bit lazy
weird = ("--[["):gsub("%W","%%%0") .. "\r?\n" // Escape "--[[", add a newline. Used in our find.
// readAll(file)
// Takes a string as input representing a filename, returns the entire contents as a string.
function readAll(file)
local c = io.open(file, "rb") // Open the file specified by the argument. Read-only, binary (Doesn't autoformat things like \r\n)
local j = c:read("*all") // Dump the contents of the file into a string.
c:close() // Close the file, free up memory.
return j // Return the contents of the string.
end
// blockActive()
// returns whether or not the weird string was matched in 'functions.lua', executes 'blockDeactivated.lua' if it wasn't.
function blockActive()
local fc = readAll("functions.lua") // Dump the contents of 'functions.lua' into a string.
if fc:find(weird) then // If it functions.lua has the block-er.
require("blockDeactivated") // Require (Thus, execute, consider loadfile instead) 'blockDeactived.lua'
return false // Return false.
else
return true // Return true.
end
end
print(blockActive()) // Test? the blockActve code.
local a = "te\st"
local b = string.gsub(a,'\','\\\\')
assert(false,b)
What am I doing wrong?
When I do assert, I want that to the screen the string te\st will be printed... but it's not working
I have a JSON file, that I want to decode it into Lua table. I don't need to print out nothing, I did the assert just to test a local problem.
So what I need is to keep all data in the JSON file that has '\'.
Use [[]] instead of "" or '' if you don't want backslash to have special meaning.
Read about literal strings in the manual.
Have you tried escaping it with the % character instead of \
I don't know if this will help, but I was having a HELL of a time making Lua's gsub match my string with special characters in it that I wanted treated literally... it turned out that instead of using \ as an escape character, or doubling the character, that I needed to prefix the special character with % to make it be treated literally.
Your question wasn't too clear so I'm not 100% sure what you mean. Do you mean that you want the assert to fire when b is equal to the string "te\st"? If so you can do a simple:
assert(b ~= "te\st")
Or I suppse...
assert(b ~= a)
You don't need the gsub. But here it is anyways.
local a = "te\\st"
local b = string.gsub(a,'\\','\\')
assert(false,b)