I am using awkc to generate an executable file from an awk script. I have the following line in an awk script abc.awk:
BEGIN{printf "Value=%s\n",(3.13+3.26)}
I have generated an executable file (abc.exe), which I have executed on different systems. It gives different outputs in floating point operations.
On one local system it gives the output 6.39 but it gives the output 6 on another system located in a different time zone.
When I searched in various sites I am able to see to set the LANG environmental variable, but how?
I'm not sure that this to do with the locale settings on your different systems but if you are looking for a floating-point number, you should use the "%f" format specifier. To get an answer to 2 decimal places, use "%.2f":
BEGIN{printf "Value=%.2f\n",(3.13+3.26)}
This should give the same result, regardless of the system it is run on.
Edit: based on the linked question, perhaps you should try using LC_NUMERIC=C to explicitly set the locale:
LC_NUMERIC=C awk 'BEGIN{printf "Value=%.2f\n",(3.13+3.26)}'
should work regardless of the system it is being run on.
Environment variables are typically something that you do not control if you hand a program over to someone else. I would look into being more specific in your printf-calls. You can format the numbers into strings in to an astonishing detail. You are probably looking for the float (%f) (you are now using a string (%s).
If you notice that you are making always the same trick with your printf-calls, you can control the number-to-string conversion settings with a variable CONVFMT in a BEGIN-block. I got introduced to this one through gawk, apparently it is however in the POSIX standard. Whether awkc supports this, I don't know.
From the gawk manual:
This string controls conversion of numbers to strings (see
Conversion). It works by being passed, in effect, as the first
argument to the sprintf() function (see String Functions). Its default
value is "%.6g". CONVFMT was introduced by the POSIX standard.
Related
I sometimes use this:
$ perl -e "printf \"%d\", ((~18446744073709551592)+1)"
24
I can't seem to do it with Raku. The best I could get is:
$ raku -e "say +^18446744073709551592"
-18446744073709551593
So: how can I make Raku give me the same answer as Perl ?
Gotta go with (my variant¹ of) Liz's custom op (in her comment below).
sub prefix:<²^>(uint $a) { (+^ $a) + 1 }
say ²^ 18446744073709551592; # 24
My original "semi-educated wild guess"² that turned out to be acceptable to #zentrunix and the basis for Liz's op:
say (+^ my uint $ = 18446744073709551592) + 1; # 24
\o/ It works!³
Footnotes
¹ I flipped the two character op because I wanted to follow the +^ form, have it sub-vocalize as "two's complement", and avoid it looking like ^2.
² One line of thinking was about the particular integer. I saw that 18446744073709551592 is close to 2**64. Another was that integers are limited precision in Perl unless you do something to make them otherwise, whereas in Raku they are arbitrary precision unless you do something to make them otherwise. A third line of thinking came from reading the doc for prefix +^ which says "converts the number to binary using as many bytes as needed" which I interpreted as meaning that the representation is somehow important. Hmm. What if I try an int variable? Overflow. (Of course.) uint? Bingo.
³ I've no idea if this solution is right for the wrong reasons. Or even worse. One thing that's concerning is that uint in Raku is defined to correspond to the largest native unsigned integer size supported by the Raku compiler used to compile the Raku code. (Iirc.) In practice today this means Rakudo and whatever underlying platform is being targeted, and I think that almost certainly means C's uint64_t in almost all cases. I imagine perl has some similar platform dependent definition. So my solution, if it is a reasonable one, is presumably only portable to the degree that the Raku compiler (which in practice today means Rakudo) agrees with the perl binary (which in practice today means P5P's perl) when run on some platform. See also #p6steve's comment below.
'Long-hand' answer:
raku -e 'put ( (18446744073709551592.base(2) - 0b1).comb.map({!$_.Int+0}).join.parse-base(2));'
OR
raku -e 'say 18446744073709551592.base(2).comb.map({!$_.Int+0}).join.parse-base(2) + 1;'
Sample Output: 24
The answers above (should?) implement "Two's-Complement" encoding directly. Neither uses Raku's +^ twos-complement operator. The first one subtracts one from the binary representation, then inverts. The second one inverts first, then adds one. Neither answer feels truly correct, yet the same answer as Perl5 is obtained (24).
Looking at the Raku Docs page, one would conclude that the "twos-complement" of a positive number would be negative, hence it's not clear what the Perl (and now Raku) answers represent. Hopefully the foregoing is somewhat useful.
https://docs.raku.org/routine/+$CIRCUMFLEX_ACCENT
Lua script:
i=io.read()
print(i)
Command line:
echo -e "sala\x00m" | lua ll.lua
Output:
sala
I want it to print all character from input, similar to this:
salam
in HEX editor:
0000000: 7361 6c61 006d 0a sala.m.
How can I print all character from input?
You tripped over one of the few places where the Lua standard library is still not 8-bit-clean.
Specifically, file reading line-by-line is not embedded-0 proof.
The reason it isn't yet is an unfortunate combination of:
Only standard C90 or equally portable constructs are allowed for the core, which does not provide for efficient 0-clean text parsing.
Every solution discussed to date on the mailinglist under that constraint has considerable overhead.
Embedded 0-bytes in text files are quite rare.
Workarounds:
Use a modified library, fixing these formats: "*l" "*L" for file:read(...)
parse your raw data yourself. (read a block using a number or as much as possible using "*a")
Badger the Lua developers/maintainers for a bugfix until they give in.
I've been trying to write a simple script compiler for a custom language used by the Game Boy Advance's Z80 processor.
All I want it to do is look at a human-readable command, take it and its arguments and convert it into a hexadecimal value into a ROM file. That's it. Each command is a byte, and each may take a different number of arguments - arguments can be either 8, 16, or 32 bits and each command has a specific number of arguments that it takes.
All of this sort of code is handled by the game and converted into workable machine code within the game's memory, so I'm not writing a full-on assembly compiler if you will. The game automatically knows how many args a command has, what each command does, exactly how to execute it as it is, etc.
For instance, you have command 0x4E, which takes in one 8-bit argument and another 32-bit argument. In hex that would obviously be 4E XX YY YY YY YY. I want my compiler to read it from text as foo 0xXX 0xYYYYYYYY and directly write it into a file as the former.
My question is, how would I do that in VB.NET? I know it's probably a very simple answer, but I see a lot of different options to write it to a file--some work and most don't for me. Could you give me some sample code as to how I would do this?
Writing an assembly compiler as I understand it is not so simple. I recomed you to use one already written see: Software Development Tools for Z80 Family
If you are still interested in writing it here are instructions:
Write the text you want to translate to some file (or memory stream)
Read it line by line
Parse the line either splitting it to an array or with regular
expressions
Identify command and arguments (as far as I remember it some commands
does not have arguments)
Translate the command to Hex (with a collection or dictionary of
commands)
Write results to an array remembering the references for jump
addresses
When everything is translated resolve addresses and write them to
right places.
I think that the most tricky part is to deal with symbolic addressees.
If you are still interested write a first piece of code (or ask how to do it) and continue with next ones.
This sounds like an assembler, even if it for a 'custom language'.
Start by parsing the command lines. use string.split method to convert the string to an array of strings. the first element in the array is your foo, you can then look that up and output 4E, then convert the subsequent elements to bytes.
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.
script(1) is a tool for keeping a record of an interactive terminal session; by default it writes to the file transcript. My problem is that I use ksh93, which has readline features, and so the transcript is mucked up with all sorts of terminal escape sequences and it can be very difficult to reconstruct the command that was actually executed. Not to mention the stray ^M's and the like.
I'm looking for a tool that will read a transcript file written by script, remove all the junk, and reconstruct what the shell thought it was executing, so I have something that shows $PS1 and the commands actually executed. Failing that, I'm looking for suggestions on how to write such a tool, ideally using knowledge from the terminfo database, or failing that, just using ANSI escape sequences.
A cheat that looks in shell history, as long as it really really works, would also be acceptable.
Doesn't cat/more work by default for browsing the transcript? Do you intend to create a script out of the commands actually executed (which in my experience can be dangerous)?
Anyway, 3 years without an answer, so I will give it a shot with an incomplete solution. If your are only interested in the commands actually typed, remove the non-printable characters, then replace PS1' with something readable and unique, and grep for that unique string. Like this:
$ sed -i 's/[^[:print:]]//g' transcript
$ sed 's/]0;cartman#southpark: ~cartman#southpark:~/CARTMAN/g' transcript | grep CARTMAN
Explanation: After first sed, PS1' can be taken from one of the first few lines of the transcript file, as is -- PS1' is different from PS1 -- and can be modified with a unique readable string ("CARTMAN" here). Note that the dollar sign at the end of the prompt was left out intentionally.
In the few examples that I tried, this didn't solve everything but took care of most issues.
This is essentially the same question asked recently in Can I programmatically “burn in” ANSI control codes to a file using unix utils? -- removing all nonprinting characters will not fix
embedded escape sequences
backspace/overstriking for underlining
use of carriage-returns for overstriking