I'm making a fully working add and subtract program as a nice little easy project. One thing I would love to know is if there is a way to restrict input to certain characters (such as 1 and 0 for the binary inputs and A and B for the add or subtract inputs). I could always replace all characters that aren't these with empty strings to get rid of them, but doing something like this is quite tedious.
Here is some simple code to filter out the specified characters from a user's input:
local filter = "10abAB"
local input = io.read()
input = input:gsub("[^" .. filter .. "]", "")
The filter variable is just set to whatever characters you want to be allowed in the user's input. As an example, if you want to allow c, add c: local filter = "10abcABC".
Although I assume that you get input from io.read(), it is possible that you get it from somewhere else, so you can just replace io.read() with whatever you need there.
The third line of code in my example is what actually filters out the text. It uses string:gsub to do this, meaning that it could also be written like this:
input = string.gsub(input, "[^" .. filter .. "]", "").
The benefit of writing it like this is that it's clear that input is meant to be a string.
The gsub pattern is [^10abAB], which means that any characters that aren't part of that pattern will be filtered out, due to the ^ before them and the replacement pattern, which is the empty string that is the last argument in the method call.
Bonus super-short one-liner that you probably shouldn't use:
local input = io.read():gsub("[^10abAB]", "")
Related
I hope I'm able to ask my question as simple as possible. I am very new to working with PowerShell.
Now to my question:
I use Invoke-Sqlcmd to run a query, which puts Data in a variable, let's say $Data.
In this case I query for triggers in an SQL Database.
Then I kind of split the array to get more specific information:
$Data2 = $Data | Where {$_.table -like 'dbo.sportswear'}
$Data3 = $Data2 | Where {$_.event -match "Delete"}
So in the end I have a variable with these Indexes(?), I'm not sure if they are called indexes.
table
trigger_name
activation
event
type
status
definition
Now all I want is to check something in the definition.
So I create a $Data4 = $Data3.definition, so far so good.
But now I have a big text and I want only the content of 2-3 specific rows.
When I used like $Data4[1] or $Data4[1..100], I realized that PowerShell sees every char as a line/row.
But when I just write $Data4 it shows me the content nice formatted with paragraphs, new lines and so on.
Has anyone an idea how I can get specific rows or lines of my variable?
Thank you all :)
It appears $Data4 is a formatted string. Since it is a single string, any indexed element lookups return single characters (of type System.Char). If you want indexes to return longer substrings, you will need to split your string into multiple strings somehow or come up with a more sophisticated search mechanism.
If we assume the rows you are after are actual lines separated by line feed and/or carriage return, you can just split on those newline characters and use indexes to access your lines:
# Array indexing starts at 0 for line 1. So [1] is line 2.
# Outputs lines 2,3,4
($Data4 -split '\r?\n')[1..3]
# Outputs lines 2,7,20
($Data4 -split '\r?\n')[1,6,19]
-split uses regex to match characters and perform a string split on all matches. It results in an array of substrings. \r matches a carriage return. \n matches a line feed. ? matches 0 or one character, which is needed in case there are no carriage returns preceding your line feeds.
I can't really seem to find a standard for this. I know inputs are taken as ASCII values, but are they required to be single characters? If not, how are multi-character inputs handled?
Command line inputs in most (if not all) programming languages are taken a line at a time. When you hit enter into a console after typing a line, the whole line gets sent into the program as a return value from the function you called to get the input.
In brainfuck, you have more control over this: You can get as many characters as you want at a time, and stop when you want to.
A single comma "," will get one byte's worth of input (a.k.a one character). If you want to handle getting a string until a newline is met, you can try implementing something like the following code (10 being the ascii value of newline and the number of repetitions of "+" and "-" chars):
[-]>,----------[++++++++++>,----------]<[<]
An array of non zero values starting and ending with zero values is saved into memory containing the ascii values of input chars.
I have a program that I am making with visual basic 2010 that will pull logs of corrupted files and give the user the location of the corrupted file(s) to fix it. These logs are huge and vary depending on the amount of corruption.
I already have set in code to only pull the lines of text that are flagged as errors but, within these lines, there are directories that point to what file is corrupted. I need to know if there is any way to read these directories and put them into a RichTextBox. Here is an example of a line from a log file:
oa = #0x238282b270->OBJECT_ATTRIBUTES {s:48; rd:NULL; on:[100]"\??\C:\Windows\WinSxS\amd64_3ware.inf.resources_31bf3856ad364e35_10.0.10130.0_en-us_ca9e7cc7a071e60f"; a:(OBJ_CASE_INSENSITIVE)}, iosb = #0x238282b250, as = (null), fa = 0,
And here is the part that I need to pull from it:
C:\Windows\WinSxS\amd64_3ware.inf.resources_31bf3856ad364e35_10.0.10130.0_en-us_ca9e7cc7a071e60f from this string
I'm pretty new to all of this, so bear with me please.
RegEx provides great flexibility for this sort of thing, but you need to establish a known pattern that defines where the path begins and ends. For instance, if it always is prefixed by on:[100]"\??\ and always ends with ";, then you could extract it with this RegEx pattern:
on:[100]"\\?\?\(.*?)";
Here's what the pattern means:
on:\[100\]"\\\?\?\\ - Matches must begin with on:[100]"\??\ exactly
The extra backslashes are necessary to escape all of the special characters which would otherwise have special meaning. In this case, [, ], \, and ? all have special meaning to RegEx, so they each need to be preceded a the backslash to escape them.
(.*?) - Matches can contain any number of any characters between the preceding on:[100]"\??\ and the following ";. The value of this portion of the input is captured as an unnamed group (i.e. group 1).
( - Begins a capturing group
. - Matches any character
* - Any number of times
? - Matches in a non-greedy fashion (i.e. only captures up through the first instance of whatever follows it in the pattern)
) - Ends the capturing group
"; - Matches must end with these two characters exactly
So, for instance:
Dim input As String = "oa = #0x238282b270->OBJECT_ATTRIBUTES {s:48; rd:NULL; on:[100]""\??\C:\Windows\WinSxS\amd64_3ware.inf.resources_31bf3856ad364e35_10.0.10130.0_en-us_ca9e7cc7a071e60f""; a:(OBJ_CASE_INSENSITIVE)}, iosb = #0x238282b250, as = (null), fa = 0,"
Dim m As Match = Regex.Match(input, "on:\[100\]""\\\?\?\\(.*?)"";")
If m.Success Then
Dim path As String = m.Groups(1).Value
End If
Or, if the input can contain multiple matches, you can loop through them like this:
For Each m As Match In Regex.Matches(input, "on:\[100\]""\\\?\?\\(.*?)"";")
Dim path As String = m.Groups(1).Value
Next
That's just an example. Depending upon your needs, you could adjust the RegEx pattern as necessary. RegEx is very flexible, so as long as there's some logical way to recognize where the path is in the string, it should be possible to find it with a RegEx pattern. On a side note, since the pattern is, itself, just a string, it can be stored in a configuration setting outside of the code too, which is an added benefit.
I have made a program which takes a 1000 digit number as input.
It is fixed, so I put this input into the code file itself.
I would obviously be storing it as Integer type, but how do I do it?
I have tried the program by having 1000 digits in the same line. I know this is the worst possible code format! But it works.
How can assign the variable this number, and split its lines. I read somewhere something about eos? Ruby, end of what?
I was thinking that something similar to comments could be used here.
Help will be appreciated.
the basic idea is to make this work:
a=3847981438917489137897491412341234
983745893289572395725258923745897232
instead of something like this:
a=3847981438917489137897491412341234983745893289572395725258923745897232
Haskell doesn't have a way to split (non-String) literals across multiple lines. Since Strings are an exception, we can shoehorn in other literals by parsing a multiline String:
v = read
"32456\
\23857\
\23545" :: Integer
Alternately, you can use list syntax if you think it's prettier:
v = read . concat $
["32456"
,"24357"
,"23476"
] :: Integer
The price you pay for this is that some work will be done (once) at runtime, namely, the parsing (e.g. read).
I am trying out a classic format string vulnerability. I want to know how exactly the following format string works:
"%NNN$hhn" where 'N' is any number.
E.g: printf("%144$hhn",....);
How does it work and how do I use this to overwrite any address I want with arbitrary value?
Thanks and Regards,
Hrishikesh Murali
It's a POSIX extension (not found in C99) which will simply allow you to select which argument from the argument list to use for the source of the data.
With regular printf, each % format specifier grabs the current argument from the list and advances the "pointer" to the next one. That means if you want to print a single value in two different ways, you need something like:
printf ("%c %d\n", chVal, chVal);
By using positional specifiers, you can do this as:
printf ("%1$c %1$d\n", chVal);
because both format strings will use the first argument as their source.
Another example on the wikipedia page is:
printf ("%2$d %2$#x; %1$d %1$#x",16,17);
which will give you the output:
17 0x11; 16 0x10
It basically allows you to disconnect the order of the format specifiers from the provided values, letting you bounce around the argument list in any way you want, using the values over and over again, in any arbitrary order.
Now whether you can use this as an user attack vector, I'm doubtful, since it only adds a means for the programmer to change the source of the data, not where the data is sent to.
It's no less secure than the regular style printf and I can see no real vulnerabilities unless you have the power to change the format string somehow. But, if you could do that, the regular printf would also be wide open to abuse.