How do you pass options to an executable? Is there an easier way than making the options boolean arguments?
EDIT: The last two answers have suggested using arguments. I know I can code a workable solution like that, but I'd rather have them be options.
EDIT2: Per requests for clarification, I'll use this simple example:
It's fairly easy to handle arguments because they automatically get parsed into an array.
./printfile file.txt 1000
If I want to know what the name of the file the user wants to print, I access it via argv[1].
Now about how this situation:
./printfile file.txt 1000 --nolinebreaks
The user wants to print the file with no line breaks. This is not required for the program to be able to run (as the filename and number of lines to print are), but the user has the option of using if if s/he would like. Now I could do this using:
./printfile file.txt 1000 true
The usage prompt would inform the user that the third argument is used to determine whether to print the file with line breaks or not. However, this seems rather clumsy.
Command-line arguments is the way to go. You may want to consider using Boost.ProgramOptions to simplify this task.
You seem to think that there is some fundamental difference between "options" that start with "--" and "arguments" that don't. The only difference is in how you parse them.
It might be worth your time to look at GNU's getopt()/getopt_long() option parser. It supports passing arguments with options such as --number-of-line-breaks 47.
I use two methods for passing information:
1/ The use of command line arguments, which are made easier to handle with specific libraries such as getargs.
2/ As environment variables, using getenv.
Pax has the right idea here.
If you need more thorough two-way communication, open the process with pipes and send stuff to stdin/listen on stdout.
You can also use Window's PostMessage() function. This is very handy if the executable you want to send the options to is already running. I can post some example code if you are interested in this technique.
The question isn't blazingly clear as to the context and just what you are trying to do - you mean running an executable from within a C++ program? There are several standard C library functions with names like execl(), execv(), execve(), ... that take the options as strings or pointer to an array of strings. There's also system() which takes a string containing whatever you'd be typing at a bash prompt, options and all.
I like the popt library. It is C, but works fine from C++ as well.
It doesn't appear to be cross-platform though. I found that out when I had to hack out my own API-compatible version of it for a Windows port of some Linux software.
You can put options in a .ini file and use the GetPrivateProfileXXX API's to create a class that can read the type of program options you're looking for from the .ini.
You can also create an interactive shell for your app to change certain settings real-time.
EDIT:
From your edits, can't you just parse each option looking for special keywords associated with that option that are "optional"?
Related
I want to get all the files of type A*.txt present in current directory via C++ code. My OS is *Nix system. Also, I want to get the names of such files.
Please suggest how can this be done.
I tried using system command but system doesn't return anything apart a integer which says if command was executed properly or not.
Thanks
There are basically three ways you can go about this.
One is to use basically what you tried before, but using the popen function, which allows you to read the output of the command(s) you run.
The second solution is to use e.g. opendir and readdir or scandir to manually filter and find the files you look for.
The third and easiest way is to use the glob function.
There is actually a fourth way as well, one which is platform independent and more C++-ish than the above methods: Using the Boost filesystem library.
I'm working on a project simulating a stock market. People buy and sell a stock and I would like to call each turn a script to try a strategy against the market.
What I want is a function in C++ which send an vector of integer as argument to a vba or python script which return an array of 3 integers.
I've searched for a solution but all i could find is a way to execute a script in python, but I don't know how I can send and get an argument from this script.
I think my problem is common but i don't know where to head to find a solution.
Thank you!
(I'm not a native english speaker so sorry if I made grammar error)
On windows you use the function CreateProcess() to start another program. Use the full path of the python interpreter as the first argument. Start the second argument with the path to the python script.
If you can fit a string representing your vector in 32768 characters, you can supply the vector in the second argument to CreateProcess.
A more flexible option is create a child process with redirected in- and output, as shown here. You can then write the vector to the standard input of the python process and read the answer back from its standard output.
There are many ways to do this.
The way I would do it is to popen() your "script" [which would be something like "python myscript.py -arg1 -arg2"]. Depending on how large your vector is, you could either store it in a file or pass it as part of the arguments [there is a limit in Windows of something like 8KB for the argument string].
The output would then appear as the result from popen()'s pipe.
Use Boost.Python. It will help you to embed python in your app.
I was looking for a solution to store program settings or options or configuration in C++. These could be settings that are exposed in a GUI and need to be saved between runs of my code.
In my search I came across boost.PropertyTree which seemed to be a good choice. I know boost is well respected code so I'm comfortable using it and so I started developing using this. Then I come across boost.program_options which seems to allow you to do the same thing but also looks more specialized for the specific use-case of program settings.
Now I'm wondering which is the most appropriate for the job? (or is there a 3rd option that is better than both)
EDIT:
fyi this is for a plugin so it will not use command line options (as in, it's not even possible).
UPDATE
I ended up sticking with boost.PropertyTree. I needed to be able to save changed options back to the INI, and I didn't see a way of doing that with boost.program_options.
Use boost::program_options. It's exactly what it's for. In one library you get command line options, environment variables options and an INI-like configuration file parser. And they're all integrated together in the Right way, so when then the user specifies the same option in more than one of these sources the library knows the Right priority order to consider.
boost::property_tree on the other hand is a more generalized library. The library parses the text stream into a uniform data model. But You need to do the real parsing -- that of making sense of the blob of data for your needs. The library doesn't know when to expect a parameter when it sees a particular option string, or to disallow specific values or types of values for a particular option.
After some digging around I think boost.PropertyTree is still the best solution because it gives me the capability to save the options after changing them from within the program which is a requirement.
There is a non-Boost possibility too. Config4Cpp is a robust, simple-to-use and comprehensively documented configuration-file parser library that I wrote. It is available at www.config4star.org.
I suggest you read Chapter 3 (Preferences for a GUI Application) of the Practical Usage Guide manual to read an overview of how Config4Cpp can do what you want. Then open the Getting Started Guide manual, and skim-read Chapters 2 and 3, and Section 7.4 (you might prefer to read the PDF version of that manual). Doing that should give you sufficient details to help you decide if Config4Cpp suits your needs better or worse than Boost.
By the way, the indicated chapters and sections of documentation are short, so they shouldn't take long to read.
Hello! I am updating some C code that copys files with a certain name. basically, I have a directory with a bunch of files named like so:
AAAAA.1.XYZ
AAAAA.2.ZYX
AAAAA.3.YZX
BBBBB.1.XYZ
BBBBB.2.ZYX
Now, In the old code, they just used a call to ShellExecute and used xcopy.exe. to get all the files starting with AAAAA, they just gave xcopy the name of the file as AAAAA.* and it knew to copy all of the files starting with AAAAA. now, im trying to get it to copy with out having to use the command line, and I am running into trouble. I was hoping CopyFile would be smart enough to handle AAAAA.* as the file to be copied, but it doesnt at all do what xcopy did. So, any Ideas on how to do this without the external call to xcopy.exe?
Check this out as a starting point
http://msdn.microsoft.com/en-us/library/aa364418(VS.85).aspx
or even better this full example
http://msdn.microsoft.com/en-us/library/aa365200(v=VS.85).aspx
You could also use SHFileOperation or IFileOperation (the latter being only available from Vista upwards but is now the recommended way according to MSDN). SHFileOperation supports wildcards and displays a progress by default, but there's also a flag for silent operation.
Check out the following MSDN links for more info:
http://msdn.microsoft.com/en-us/library/bb762164(v=VS.85).aspx
http://msdn.microsoft.com/en-us/library/bb775771(v=VS.85).aspx
You would basically have to write code to reproduce the functionality in xcopy. To do so, you must build a list of files by accessing the path and recursing through it. Test each found entry with your pattern and keep only those that match. Then iterate over that list with CopyFile.
See the following set of functions that can help you build the file list:
http://en.wikipedia.org/wiki/Dirent.h
It might just be easier to keep using xcopy unless you have a specific reason not to.
There are lots of ways to do it. I'd probably use a loop of FindFirstFile() / FindNextFile().
However, is there any reason you can't still use xcopy? You can launch it with CreateProcess(). It isn't pretty, but it works.
Imaging that a program needs to know quite a lot of parameters to do its tasks properly, such as 'Port = 2323' this kind of things.
now I want to save these parameters in a plain text file, similar to Unix' system variables such as users and groups.
Is there any standard way/libraries that can help me to do this? Does anyone ever used them before? thanks
Boost.Program_options library. Is this you are looking for?
The program_options library allows program developers to obtain program options, that is (name, value) pairs from the user, via conventional methods such as command line and config file.
Qt offers this by default, and in a cross-platform way. Checkout out QSettings
You can also create an alias or shell script that executes your program with given parameters. To conviniently get these parameters there's "getopt"
Link here for a cross platform ini handler.
Hope this helps.