How can I list directory contents in GnuCOBOL? - cobol

I know my question is rather generic (and it looks like "please do all of my work for me"), so let me make it somewhat clearer: I'm - more or less - a COBOL beginner, the only thing I've done with it so far was a small FastCGI application for a single-serving page, just to have done something with it.
Now I'm considering to write a small file server in GnuCOBOL so I have something real to work with. I tend to learn new languages by writing stuff in them. While I do have an idea about how to read and process a specific file now, I still could need a clue about how I can collect and handle a specified directory's contents.
Sadly, the system calls C$LIST-DIRECTORY,x"91" function 69, CBL_DIR_SCAN_START and its sibling methods are still on the GnuCOBOL Wish List, so I can't just adapt existing solutions from the commercial COBOLs. I'm somewhat lost here.

call "system" using "dir /b > fileslist.txt" end-call
And then read in the listing file ...

Related

What is the recommended way to make & load a library?

I want to make a small "library" to be used by my future maxima scripts, but I am not quite sure on how to proceed (I use wxMaxima). Maxima's documentation covers the save(), load() and loadFile() functions, yet does not provide examples. Therefore, I am not sure whether I am using the proper/best way or not. My current solution, which is based on this post, stores my library in the *.lisp format.
As a simple example, let's say that my library defines the cosSin(x) function. I open a new session and define this function as
(%i0) cosSin(x) := cos(x) * sin(x);
I then save it to a lisp file located in the /tmp/ directory.
(%i1) save("/tmp/lib.lisp");
I then open a new instance of maxima and load the library
(%i0) loadfile("/tmp/lib.lisp");
The cosSin(x) is now defined and can be called
(%i1) cosSin(%pi/4)
(%o1) 1/2
However, I noticed that a substantial number of the libraries shipped with maxima are of *.mac format: the /usr/share/maxima/5.37.2/share/ directory contains 428 *.mac files and 516 *.lisp files. Is it a better format? How would I generate such files?
More generally, what are the different ways a library can be saved and loaded? What is the recommended approach?
Usually people put the functions they need in a file name something.mac and then load("something.mac"); loads the functions into Maxima.
A file can contain any number of functions. A file can load other files, so if you have somethingA.mac and somethingB.mac, then you can have another file that just says load("somethingA.mac"); load("somethingB.mac");.
One can also create Lisp files and load them too, but it is not required to write functions in Lisp.
Unless you are specifically interested in writing Lisp functions, my advice is to write your functions in the Maxima language and put them in a file, using an ordinary text editor. Also, I recommend that you don't use save to save the functions to a file as Lisp code; just type the functions into a file, as Maxima code, with a plain text editor.
Take a look at the files in share to get a feeling for how other people have gone about it. I am looking right now at share/contrib/ggf.mac and I see it has a lengthy comment header describing its purpose -- such comments are always a good idea.
For principiants, like me,
Menu Edit:configure:Startup commands
Copy all the functions you have verified in the first box (this will write your wxmaxima-init.mac in the location indicated below)
Restart Wxmaxima.
Now you can access the functions whitout any load() command

Does Ruby on Rails have read stream for files?

Does rails have a way to implement read streams like Node js for file reading?
i.e.
fs.createReadStream(__dirname + '/data.txt');
as apposed to
fs.readFile(__dirname + '/data.txt');
Where I see ruby has
file = File.new("data.txt")
I am unsure of the equivalent in ruby/rails for creating a stream and would like to know if this is possible. The reasons I ask is for memory management as a stream will be delivered piece by piece as apposed to one whole file.
If you want to read a file in Ruby piece-by-piece, there are a host of methods available to you.
IO#each_line/IO::foreach, also implemented in File to iterate over each line of the file. Neither reads the whole file into memory; instead, both simply read up until the next newline, return, and pause reading, barring a possible buffer.
IO#read/IO::read takes a length parameter, which allows you to specify for it to read up to length bytes from the file. This will only read that many, and not the whole thing.
IO::binread does the same as IO::read, but will open the file in binary mode.
IO#readpartial appears to be very similar or identical to IO#read, but is also worth looking at.
IO#getc and IO#gets both read from the file until they reach the end of what they'll return, as far as I can tell.
There are several more that I'm looking for right now.

Any best practice around having different data in /priv for testing vs production?

I'm writing tests with EUnit and some of the Units Under Test need to read a data file via file:consult/1. My tests make assumptions about the data that will be available in /priv, but the data will be different in production. What's the best way to accomplish this?
I'm a total newbie in Erlang and I have thought of a few solutions that feel a bit ugly to me. For example,
Put both files in /priv and use a macro (e.g., "-ifdef(EUNIT)") to determine which one to pass to file:consult/1. This seems too fragile/error-prone to me.
Get Rebar to copy the right file to /priv.
Also please feel free to point out if I'm trying to do something that is fundamentally wrong. That may well be the case.
Is there a better way to do this?
I think both of your solutions would work. It is rather question of maintaining such tests, and both of those rely on some external setup (file existing, and having wright data).
For me easiest way to keep contents of such file local to given test is mocking, and making file:consult/1 return value you want.
7> meck:new(file, [unstick, passthrough]).
ok
8> meck:expect(file, consult, fun( _File ) -> {some, data} end).
ok
9> file:consult(any_file_at_all).
{some,data}
It will work, but there are two more things you could do.
First of all, you should not be testing file:consult/1 at all. It is part of standard library, and can assume it works all wright. Rather than doing that you should test functions that use data you read from this file; and of course pass to them some "in-test-created" data. It will give you some nice separation between data source, and parsing (acting on) it. And later it might be simpler to replace file:consult with call to external service, or something like that.
Other thing is that problem with testing something should be sign of bad smell for you. You might think a little about redesigning your system. I'm not saying that you have to, but such problems are good indicator to justify on . If you testing some functionality x, and you would like it to behave one way in production and other in tests (read one file or another), than maybe this behaviour should be injected to it. Or in other words, maybe file your function should read should be a parameter in this function. If you would like to still have some "default file to read" functionality in your production code, you could use something like this
function_with_file_consult(A, B, C) ->
function_with_file_consult(A, B, C, "default_file.dat").
function_with_file_consult(A, B, C, File) ->
[ ... actual function logic ... ]
It will allow you to use shorter version in production, and longer just for your tests.

Is it possible to edit and recompile an iOS Binary?

I have an application and posted to Cydia recently. It has been cracked by someone else and posted it in torrent sites. I have a binary checksum verification mechanism inside and they were able to create a new checksum file based on the changes they have made to the binary. They have edited two functions and decompiled it and posted it to torrents.
I saw that it's possible to see the actual implementation of functions and classes. But in order to edit the functions they have to find the address of that function and edit it via HEX EDITOR. I don’t want to make it "unhackable", but I really want to find out how they hack.
How can I edit a function in an iOS binary and re-compile it? For example I have a following method in one of my classes.
- (id) getSomething {
return #"Something";
}
I want to edit the return value of this function. Is that possible?
Usually, you don't "re-compile" it. Just feed the file to IDA, look for strings, function calls or whatever you are looking for and then use a hex editor or similar to edit the file on assembly level. In most cases it's enough to simply change a conditional jump into an unconditional jump or a nop (no operation). If you want to change return values, you have to put a little more effort into it, but in my experience you either edit the char sequence right inside the binary file, if it's specified as a constant or initial value - or you just write a completely new function and "copy" the assembler code of it into the original file. You just have to make sure your new function does not take more space than the original - or everything's getting a lot more complex.
I hope that's what you were asking for, otherwise just tell us which app you are talking about and we can look deeper into it :)

In rails.vim why do I get "E345 can't find file in path" errors?

I've been learning Ruby/Rails with vim. Tim Pope's rails.vim seems like a really good tool to traverse files with, but I keep getting these pesky "E345 can't find file in path" errors. I'm not vim expert yet, so the solution isn't obvious. Additionally, I've tried this and it doesn't apply to my problem.
As an example of the problem. I have a method format_name defined in app/helpers/application_helper.rb and it is used in app/helpers/messages_helper.rb. Within the latter file I put my cursor over the usage of format_name and then hit gf and I get that error. Similar disfunction with commands like ]f and [f
However, it works sometimes. I was able to gf from user to the app/models/user.rb
Ideas?
I think that is a limitation of rails.vim. It does not support “finding” bare methods. Supporting something like that would require one of the following:
an exhaustive search of all the source files for each “find” request
(which could be expensive with large projects),
“dumb” indexing of method names
(e.g. Exuberant Ctags and gControl-]; see :help g_CTRL-]), or
smart enough parsing of the code to make a good guess where the method might be defined
(which is hard to do properly).
If you know where the method is, you can extend many of the navigation commands with a method name:
:Rhelper application#format_name
But, you do not have to type all of that in. Assuming the cursor is on format_name you can probably just type:RhTabspaceappTab#Control-R Control-W (see :help c_CTRL-R_CTRL-W).

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