I am using int res = system("uname -p"); in my c++ code.
It will give the the result in standard output by using
fprintf(stdout,"execution returned %d.\n",res);
I want to store this result string in a variable, I am unable to store it.
I google it but unable to find proper solution, Can any one tell me the correct way.
First, you don't need to run the uname command programmatically to get your processor. You can simply run the uname(2) syscall (which the uname command invokes). And you could also read and parse /proc/cpuinfo from your program.
If you wanted to read the output of some command, use popen(3) library function.
See also my answer to a related question.
Related
I have a c++ program that run a command and pass some arguments to it. The code is as follow:
int RunApplication(fs::path applicationPathName,std::string arguments)
{
std::string applicationShortPath=GetShortFileName(applicationPathName);
std::string cmd="\""+applicationShortPath +"\" "+ arguments+" >>log.txt 2>&1 \"";
std::cout<<cmd<<std::endl;
int result=std::system(cmd.c_str());
return result;
}
When I run system command, the cmd window appears shortly and then closes, but the result is 1 and the cmd was not run (the command should generate output which is not generated).
To check that the cmd is correct, I stopped the application just before system line and copy/ paste cmd content to a cmd window and it worked.
I am wondering how can I find why application is not run in system()?
the cmd has this value just before running it:
"D:/DEVELO~3/x64/Debug/enfuse.exe" -w --hard-mask --exposure-weight=1 --saturation-weight=0.328 --contrast-weight=0.164 -o "C:/Users/m/AppData/Local/Temp/1.tif" "C:/Users/m/AppData/Local/Temp/1.jpg" "C:/Users/m/AppData/Local/Temp/2.jpg" >>log.txt 2>&1 "
How can I find why it is not working?
Is there any way that I set the system so it doesn't close cmd window so I can inspect it?
is there any better way to run a command on OS?
Does Boost has any solution for this?
Edit
After running it with cmd /k, I get this error message:
The input line is too long.
How can I fix it other than reducing cmd line?
There are two different things here: if you have to start a suprocess, "system" is not the best way of doing it (better to use the proper API, like CreateProcess, or a multiplatform wrapper, but avoid to go through the command interpreter, to avoid to open to potential malware injection).
But in this case system() is probably the right way to go since you in fact need the command interpreter (you cannot manage things like >>log.txt 2>&1 with only a process creation.)
The problem looks like a failure in the called program: may be the path is not correct or some of the files it has to work with are not existent or accessible with appropriate-permission and so on.
One of the firt thing to do: open a command prompt and paste the string you posted, in there. Does it run? Does it say something about any error?
Another thing to check is how escape sequence are used in C++ literals: to get a '\', you need '\\' since the first is the escape for the second (like \n, or \t etc.). Although it seems not the case, here, it is one of the most common mistakes.
Use cmd /k to keep the terminal: http://ss64.com/nt/cmd.html
Or just spawn cmd.exe instead and inspect the environment, permissions, etc. You can manually paste that command to see whether it would work from that shell. If it does, you know that paths, permssions and environment are ok, so you have some other issue on your hands (argument escaping, character encoding issues)
Check here How to execute a command and get output of command within C++ using POSIX?
Boost.Process is not official yet http://www.highscore.de/boost/process/
What I'd like to do is have my C++ code open up Mplus (statistical program that I've downloaded on my computer) and run it. Is it possible?
You may be able to do what you want with std::system() calls like:
std::system("program -e input_commands.txt"); // Assuming it accepts some sort of command line args
std::system("program < input_commands.txt"); // Assuming it responds to stdin
It depends on the program if this approach will work.
I have a quick question, should be relatively simple for those who have some more experience in WMI-command processor than I do (and since I'm an absolute beginner thats not hard :-) )
I fail to understand why wmic /format switch works the way it does. I open up cmd.exe and type
wmic process list brief /format:htable > processlist.html
this does exactly what I want and no bothers further on. Whereas if I go to wmic processor, and try to execute the same command exactly as above...
wmic:root\cli>process list brief /format:htable > processlist.html
I receive the error tag: "Invalid XSL format (or) file name."
Here goes the screenshot. Note I have already copied XSL files from wbem to sys32 dir
Can someone explain to me why these 2 commands that for me look exactly the same, with the only difference that one is executed outside wmic environment and the other one is from inside, the latter one doesn't work? I just fail to understand it.
Please advise so I can comprehend this a bit better! :-)
Try this
copy /y %WINDIR%\system32\wbem\en-US\*.xsl %WINDIR%\system32\
And then
wmic:root\cli>process list brief /format:htable.xsl > processlist.html
Note the presence of the extension after "htable"
You are attempting to use CMD.EXE > redirection while you are within the interactive WMIC context. That can't work.
You can use the WMIC /output:filename switch while in interactive mode. Each subsequent command will overwrite the output of the previous command. You can get multiple commands to go to the same file by using /append:filename instead. You can reset the output back to stdout using /output:stdout.
/output:processlist.html
process list brief /format:htable
/output:stdout
Did you try specifying a full path in the wmic:root\cli>process call? My bets are that the first worked because it output the file to the current directory.
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.
I am using execv() to run commands from /bin/ such as 'ls', 'pwd', 'echo' from my c++ program, and I am wondering what value I should provide in argv[0];
const char * path = getPath();
char ** argv = getArgs();
execv(path,argv);
argv[0] is supposed to be the program name. It's passed to the program's main function. Some programs differentiate their behavior depending on what string argv[0] is. For example the GNU bash shell will disable some of its features if called using sh instead of bash. Best give it the same value that you pass to path.
In linux, argv[0] is the process name displayed by the top utility (which it probably gets from reading entries in /proc/)
argv[0] should be the full path of the command that you want to run.
I know that this is not the answer you're looking for but is there a specific reason why you're doing this? The reason I ask is that most if not all of the actions people normally run with either system() or execv() are available in libraries on either Windows or Unix and are safer, faster and less likely to suffer from circumstantial errors. By that I mean, for example, when the PATH changes and suddenly your code stops working.
If you're passing in a string, either in whole or in part, and running it then you also leave yourself open to a user gaining access to the system by entering a command that could be damaging. E.g. imagine you've implemented a file search using find /home -name and your user types in:
"%" -exec rm {} \;
Ouch!