I'm trying to execute a command using std::system from Unreal Engine C++
FString command = FString("start /B cmd /k python \"D:/app.py\"");
std::string comm(TCHAR_TO_UTF8(*command));
std::system(comm.c_str());
The command itself is working as expected, however, I need it to execute on the current thread, or alternatively check if it's finished before continuing because the next operations depend on the completion of this command
Is there a way to do it? or maybe I should use another command?
Thanks, Eden
The std::system function will not return until the command you execute have finished running.
Also on Windows (which you seem to be running) then system will invoke the command interpreter (cmd) for execution of the command, which means the command you want to execute must be in the command interpreters PATH (or be an internal command of the command interpreter).
If python is in the PATH, then you could run the python command directly, without using start or cmd (especially since then you would have two instances of cmd running), and the system function would block and not return until the python command finished running:
FString command = FString("python \"D:/VRoscopy_repo/VRoscopy/conversion/invesalius3-master/app.py\" --no-gui -i \"D:\VRoscopy_repo\DICOM\Human\MedDream\Body\" -t 200,3033 -e \"D:\VRoscopy_repo\DICOM\Human\MedDream\Body/VRoscopy27777BED4B650CE6AFE884B365C56BCC.stl\"");
Related
I am trying to launch a legacy application in GDB, and it requires that it's argv[0] value not contain anything other than alphanumeric characters.
Whenever I launch the program in GDB it seems that it expands the name to be the full path before running the program, so I get an error like (because it can't deal with the slashes):
"Cannot find /home/user/myapp ..."
Is it possible to run a program in GDB with a relative path, so that it will just see "myapp"?
Gdb normally runs target commands using the shell command line
exec program_pathname program_arguments
But it has a set exec-wrapper command that will change this to
exec exec_wrapper program_pathname program_arguments
The exec_wrapper is often another command, but it can be an option that the exec command accepts.
Many shells (bash, zsh, ksh93) support a -a option to the exec command to set argv[0].
So, if your shell supports exec -a, you can do the following to invoke /home/user/myapp with argv[0]==myapp:
(gdb) set exec-wrapper -a myapp
I am new to Lua programming language. I installed Lua for Windows v5.1.5-52. I want to use luacom library to run shell script. Here is my code,
local luacom = require('luacom');
local shell = luacom.CreateObject("WScript.Shell")
shell:Run ('echo 123', 0)
which throws the following error:
lua: COM exception:(.\src\library\tLuaCOM.cpp,398):The system cannot
find the file specified.
I looked for tLuaCOM.cpp file, but could not find it, not even folder src. Though I found luacom.dll in clibs folder.
Is there any workaround with this problem?
tLuaCOM.cpp is a luacom source file, so it's probably not on your PC, except you've build it yourself.
The error comes from one of the calls - either CreateObject() or Run.
The Run Method (Windows Script Host) helps says that it starts processes:
The Run method starts a program running in a new Windows process.
but echo is a shell command, not an executable, so you have to start an instance of the Windows command interpreter and pass your command like:
shell:Run('cmd /c "echo 123"')
Well, I will put it plain and simple: I am a C++ pleb. Still trying to learn though.
My question is: is it possible to run a command though the terminal using system() command without letting the command be shown in the console/terminal?
Example:
system("sudo service sshd start") ;
Output: Sudo service sshd start
Where as I want:
system("sudo service sshd start") ;
output: (Blank)
Note: I am on linux.
The system standard library function starts up a subshell and executes the provided string as a command within that subshell. (Note that a subshell is simply a process running a shell interpreter; the particular shell interpreter invoked by system will depend on your system. No terminal emulator is used; at least, not on Unix or Unix-like systems.)
The system function does not reassign any file descriptors before starting the subshell, so the command executes with the current standard input, output and error assignments. Many commands will output to stdout and/or stderr, and those outputs will not be supressed by system.
If you want the command to execute silently, then you can redirect stdout and/or stderr in the command itself:
system("sudo service sshd start >>/dev/null 2>>/dev/null") ;
Of course, that will hide any error messages which might result from the command failing, so you should check the return value of system and provide your own error message (or log the information) if it is not 0.
This really has very little to do with the system call or the fact that you are triggering the subshell from within your own executable. The same command would have the same behaviour if typed directly into a shell.
I have built a bash script to start up some processes in my system. It simply calls the process and associated config file. Same as I would call from the command line.
#!/bin/bash
# Start specified process in a new session
setsid $1 &>/dev/null &
So to start up someprocess, I would call from the command line:
root#supercomputer:~# start someprocess
This works like a charm. Every process, every time. But when I make a system call from a different running C++ process, someprocess never starts up.
system( "start someprocess" )
This approach for 90% of my processes, except for one. The only difference in the working and not working processes is that the non-working one uses proprietary libraries underneath. I recently added the setsid option to the bash script in hopes that starting a new session would help, but it made no difference. I've also tried popen, and execv. No change.
So my question is what is the difference between calling something with system() and just making that same call from the command line?
All processes are written in C++ on Linux.
.bashrc is only invoked if bash is run as interactive, non-login shell. If it's invoked as non-interactive shell, as when using system() on a script with a bash shebang, it only reads the configuration file pointed to by $BASH_ENV.
That means you have the following options:
add -l to the shebang - causes the shell to read ~/.profile at startup
set $BASH_ENV to the script you want sourced before calling system()
add -i to the shebang - invokes bash as interactive shell and causes it to read ~/.bashrc, but will also effect how bash handles input/output.
I'd recommend the first option.
You can find a detailed explanation of how bash reads it's startup files here. I'm not sure this will solve your problem completely, but it may at leas shed some light on that part of the issue.
Check the environment variables that are used in the system() call. For example, call system to print out some of the variables, and see if they match what you see from the command line.
Likely they are not being sourced correctly.
I have a question regarding executing shell commands in c++. I'm building an application in winforms, vs 2008. My application has a button, when clicked should decode a binary file to a .csv file. I can decode files by first going to the right directory (cd Test_Copy2) and then execute a command in the command prompt (java -jar tool.jar -b x.fit x.csv). I tried a lot of different stuff but unfortunately got none to work!
I tried using:
system, _popen, ShellExecute(NULL, L"open", L"C:\\WINDOWS\\system32\\cmd.exe ", L"java -jar Tool.jar -b x.fit x.csv", L"C:\\Test_Copy2", SW_SHOWNORMAL)
Can anyone please provide me with an example on how to do that? I dont know where I'm going wrong, most of the time the command prompt opens but no command is executed!
If you really want to run the jar in a cmd.exe instance, you need to add one of the correct command line switches to cmd.exe for it to work the way you want it to:
/C Carries out the command specified by string and then terminates
/K Carries out the command specified by string but remains
For instance, your command string should be:
C:\\WINDOWS\\system32\\cmd.exe /c java -jar Tool.jar -b x.fit x.csv
You can use the system() function to execute shell commands.
For example:
system("DIR") executes the DIR command in the CMD shell. The default directory at the start is the directory you're .exe file is located.
'system("PAUSE")` executes the PAUSE command.
The command/s you wannt to execute should be passed as a constant string to the function.
Edit:
For you paritcular program the syntax (IMO) would be:
system("java -jar Tool.jar -b x.fit x.csv")