On 10/08/2014 05:54 AM, Jan Vávra wrote:
> Hello,
> there are several tips how to run a child process ($cmd) in background on
> Windows. Firstly I used popen:
> |function execInBackground($cmd)
> {
> $cmd = 'start /B "" ' . $cmd;
> pclose(popen($cmd, "r"));
> }
>
> Using of popen has unexpected side effect. If somebody locks a file, the child
> process inherits the file lock Windows handle and the file is locked by the
> child process. The child process application don't know about it.
>
> I needed to call a child simple http server that wraps the java code and I
> made a file locks in php to make a critical section for launching the simple
> java http server. And the lock is held forever by the java child process.
>
> This problem is caused by the inherit_handle parameter set to TRUE in
> CreateProcess function in the proc_open Windows implementation.
>
> This problem is more probable. If someone uses log4php the log files are file
> locked and the child process holds the logs. So the logs cannot be deleted etc.
>
> I also tried to use
> function execInBackground($cmd)
> {
> $cmd = "c:\tmp\PSTools\PsExec.exe -d ".$cmd;
> exec($cmd);
> }
> This implementation doesn't have problem with file locks as described above
> but opens a console window for a child process.
>
> So I had to write my PsExec.exe equivalent in c++:
> int main(int argc, char **argv)
> {
> DWORD cpError = ERROR_SUCCESS;
> if (argc>1)
> {
> std::string cmdline = argv[1];
> for (int i=2; i<argc; i++)
> {
> cmdline=cmdline+" "+argv[i];
> }
>
> STARTUPINFO si;
> PROCESS_INFORMATION pi;
>
> ZeroMemory( &si, sizeof(si) );
> si.cb = sizeof(si);
> ZeroMemory( &pi, sizeof(pi) );
>
> // Start the child process.
> if( !CreateProcess( NULL, // No module name (use command line).
> (LPSTR)cmdline.c_str(), // Command line.
> NULL, // Process handle not inheritable.
> NULL, // Thread handle not inheritable.
> FALSE, // Set handle inheritance to FALSE.
> CREATE_NO_WINDOW, // 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.
> )
> {
> cpError = GetLastError();
> printf( "CreateProcess failed (%d).\n", cpError );
> return 1;
> }
>
> // DONT wait until child process exits.
> //WaitForSingleObject( pi.hProcess, INFINITE );
>
> // Close process and thread handles.
> CloseHandle( pi.hProcess );
> CloseHandle( pi.hThread );
> }
>
> return cpError;
> }|
>
> I think It would be nice to have a function exec_in_background(.) that does it
> directly in the php core.
> Jan.
>
PCNTL [1] will allow you to fork a process. It isn't usually included in the
standard build of PHP.
1) http://php.net/manual/en/book.pcntl.php
--
Jim Lucas
http://www.cmsws.com/
http://www.cmsws.com/examples/
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