I have a problem related to passing arguments to a C++ compiled executable. The program emulate the behaviour of a particular inference engine: the setup of the engine is load at runtime from an XML file, and then I want to call it from command line with different input values.
The characteristic of the input are:
Every time that I call the program, the input structure is different, because the system itself is different.
The input is a set of couple {name, value}, one for each part of the system.
I have to separate the configuration XML from the input.
I call the program from a PHP or Node.js server, since it return a result that I expose to the outside through an API.
Input value are obtained from an HTTP post request.
By now I have tried these solutions:
Pass it from the command line ex: "./mysoftware input1 value1 input2 value2 ...etc". A little unconfortable, since I have up to 200 input.
Create a file with all the couples name,value and then call the program that parse the file and then destroy at the end. This is a bottleneck of performance for my API, because at every call I have to create and destruct a file.
Does anyone know a better way to approach this problem?
3. Pass the values to the program via the standard input stream and read them from std::cin inside your C++ program.
Related
I have a .lua file as follows:
timeout = 3000
index = 15
function Test()
A(index, timeout)
B()
end
Test()
A and B fuctions are implemented in the c++. It will be excuted with a 'luaL_dofile(L, "test.lua");' in c++.But the timeout and the index will change at different times.
The question is how to modify the params in real time?
I'm going to write two c++ programs.First one is to sent .lua string to the sencond one. The second c++ program implemets the A and B and will dofile the lua script. But the timeout and the index will changes very often. How to do that? My solution is to parse the index and timeout string ,then write the current value to the file in the first c++ program.Any better solution?
Instead of modifying a lua script over and over to call A with different arguments, you should probably just list all arugments in a single script.
local listOfIndices = {1,5,23,124,25,}
local timeout = 3000
for _,index in ipairs(listOfIndices) do
A(index, timeout)
B()
end
Otherwise having 10000 different indices will result in 10000 file write and read operations.
If you're on Windows you might want to give this a read https://learn.microsoft.com/de-de/windows/win32/ipc/interprocess-communications?redirectedfrom=MSDN
I can think of better ways to have two programs communicate, than sending Lua scripts through files.
Also I'm not sure why you need two applications here, why not add whatever applicaton 2 does to application 1 as a library?
I've been modifying an example C++ program from the Caffe deep learning library and I noticed this code on line 234 that doesn't appear to be referenced again.
::google::InitGoogleLogging(argv[0]);
The argument provided is a prototxt file which defines the parameters of the deep learning model I'm calling. The thing that is confusing me is where the results from this line go? I know they end up being used in the program because if I make a mistake in the prototxt file then the program will crash. However I'm struggling to see how the data is passed to the class performing the classification tasks.
First of all, argv[0] is not the first argument you pass to your executable, but rather the executable name. So you are passing to ::google::InitGoogleLogging the executable name and not the prototxt file.
'glog' module (google logging) is using this name to decorate the log entries it outputs.
Second, caffe is using google logging (aka 'glog') as its logging module, and hence this module must be initialized once when running caffe. This is why you have this
::google::InitGoogleLogging(argv[0]);
in your code.
I've got a series of cpp source file and I want to write another program to JUDGE if they can run correctly (give input and compare their output with standart output) . so how to:
call/spawn another program, and give a file to be its standard input
limit the time and memory of the child process (maybe setrlimit thing? is there any examples?)
donot let the process to read/write any file
use a file to be its standard output
compare the output with the standard output.
I think the 2nd and 3rd are the core part of this prob. Is there any way to do this?
ps. system is Linux
To do this right, you probably want to spawn the child program with fork, not system.
This allows you to do a few things. First of all, you can set up some pipes to the parent process so the parent can supply the input to the child, and capture the output from the child to compare to the expected result.
Second, it will let you call seteuid (or one of its close relatives like setreuid) to set the child process to run under a (very) limited user account, to prevent it from writing to files. When fork returns in the parent, you'll want to call setrlimit to limit the child's CPU usage.
Just to be clear: rather than directing the child's output to a file, then comparing that to the expected output, I'd capture the child's output directly via a pipe to the parent. From there the parent can write the data to a file if desired, but can also compare the output directly to what's expected, without going through a file.
std::string command = "/bin/local/app < my_input.txt > my_output_file.txt 2> my_error_file.txt";
int rv = std::system( command.c_str() );
1) The system function from the STL allows you to execute a program (basically as if invoked from a shell). Note that this approach is inherenly insecure, so only use it in a trusted environment.
2) You will need to use threads to be able to achieve this. There are a number of thread libraries available for C++, but I cannot give you recommendation.
[After edit in OP's post]
3) This one is harder. You either have to write a wrapper that monitors read/write access to files or do some Linux/Unix privilege magic to prevent it from accessing files.
4) You can redirect the output of a program (that it thinks goes to the standard output) by adding > outFile.txt after the way you would normally invoke the program (see 1)) -- e.g. otherapp > out.txt
5) You could run diff on the saved file (from 3)) to the "golden standard"/expected output captured in another file. Or use some other method that better fits your need (for example you don't care about certain formatting as long as the "content" is there). -- This part is really dependent on your needs. diff does a basic comparing job well.
I have a C++ program which is mainly used for video processing. Inside the program, I am launching the system command in order to obtain pass the processed videos to some other binaries to postprocess them.
I have a while loop towards infinite and I am launching the system command inside the loop every time. The thing is that at a certain point I am receiving the -1 return code from the system command. What could be the reason for that?
Inside the system command I am just calling a binary file with the adequate parameters from the main project.
The system command which I want to execute is actually a shell file.
In this file I am extracting the main feature from the video and passing them through a SVM model from a 3D party library in order to obtain the the desired classification.
./LiveGestureKernel ./Video ./SvmVideo
./mat4libsvm31 -l SvmVideoLabels < SvmVideo > temp_test_file
./svm-predict temp_test_file svm_model temp_output_file
cat < temp_output_file
rm -f temp_*
After a certain number of iterations through the while loop, it just won't execute the script file and I cannot figure out the reason for this. Thanks!
If you get -1 from the call to system(), you should first examine the contents of errno - that will most likely tell you what your specific problem is.
The one thing to watch out for is that the return value from system is an implementation-defined one in the case where you pass it a non-NULL command, so it's possible that -1 may be coming from your actual executable.
Your best bet in that case is to print out (or otherwise log) the command being executed on failure (and possibly all the time), so that you can check what happens with the same arguments when you execute it directly from a command line or shell.
Actually I have trouble naming the title of this post. Because I don't know how to summarize my meaning in a professional way. But I'll explain my question as below:
I'm running a program written by C++, command is:
./VariationHunter_SC
Then it'll let you type in many parameters:
Please enter the minimum paired-end insert size:
Please enter the maximum paired-end insert size:
Please enter the pre-processing mapping prune probability:
Please enter the name of the input file:
Please enter the minimum support for a cluster:
Obviously I need to type in such parameters one by one to run the program; But I have thousands of such jobs, and need to pre-assign such parameters in script, and submit script to computer.
So how can I do that?
thx
Edit
so how can I make parameter-list?
Just like below?:
140
160
0
mrfast.vh
1
Seems the program cannot recognize these numbers, and distribute numbers..
This depends on how the program actually reads the data that you type in - it's likely that its reading stdin, so you could use separate files with the parameters and pass them in via redirection: ./VariationHunter_SC < parameter-file
It's also possible that the program will accept parameters on the command line, but there's no way of really knowing that (or how) except by whatever documentation the program might come with (or by reading the source code, if it's available and there is no other accurate docs).
Simply use the piping character to pipe the contents of a file to your program
example, in a windows command shell:
echo "asdf" | pause
This will pass "asdf" to the pause program. As a result, pause will print a "Press any key to continue" message, then imediately continue because it will receive the "asdf" string as a response.
So, overall, write or use a program that outputs the contents of your file. Call it, then pipe its output to the program that needs the input.
The unix cat command is such a command that writes the contents of a file to output, or to the input of another executable if you are piping the output.