Launching an application from a thread with C++ - c++

Question

I need to launch a 3rd party program inside a thread, wait to get the results both from stdout/stderr with C++.
What methods are available?
Are they cross-platform? I mean, can I use them both for cl/gcc?

Answer 1

On Unix:
http://linux.die.net/man/3/execl
#include <sys/types.h>
#include <unistd.h>
void run_process (const char* path){
pid_t child_pid;
/* Duplicate this process. */
child_pid = fork ();
if (child_pid != 0){
/* This is the parent process. */
int ret = waitpid(child_pid, NULL, 0);
if (ret == -1){
printf ("an error occurred in waitpid\n");
abort ();
}
}
else {
execl (path, path);
/* The execvp function returns only if an error occurs. */
printf ("an error occurred in execl\n");
abort ();
}
}
On Windows:
http://msdn.microsoft.com/en-us/library/ms682425%28v=vs.85%29.aspx
# include <windows.h>
void run_process (const char* path){
STARTUPINFO si;
PROCESS_INFORMATION pi;
ZeroMemory( &si, sizeof(si) );
si.cb = sizeof(si);
ZeroMemory( &pi, sizeof(pi) );
bool ret = = CreateProcess(
NULL, // No module name (use command line)
path, // Command line
NULL, // Process handle not inheritable
NULL, // Thread handle not inheritable
false, // Set handle inheritance to FALSE
0, // No creation flags
NULL, // Use parent's environment block
NULL, // Use parent's starting directory
&si, // Pointer to STARTUPINFO structure
&pi // Pointer to PROCESS_INFORMATION structure
)
if (!ret){
printf("Error");
abort();
}
WaitForSingleObject(pi.hProcess, INFINITE);
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
}

Answer 2

system should be platform independant, but you might want to stick with createprocess (win)/ exec (others) if there is a concern about running the program with the same security privledges.

Answer 3

There is a set of posix functions to launch an external executable - see exec - which are cross platform. To do some specific tasks on windows you may need to use windows specific createprocess.
These generally block so you would have to start them in a new thread. Threading is generally not cross platform, although you can use posix (pthreads) on windows.
An alternative is to use somthing like Qt or wxWidgets cross platform libraries.