On Jan 21, 2011, at 1:45 PM, Richard Hipp wrote:
> But I did not accept that branch onto the trunk. I want to do the "hooks"
> via a different mechanism. But in order to implement this different
> mechanism, I need example C code for launching a background process in
> windows that is not associated with an console. Doing that is easy in Unix,
> but I'm not sure how to do it in windows.
>
> This background process would be responsible for waiting until the push/pull
> finished and then running whatever hooks are required.
I haven't programmed on Windows for ages, and maybe it's not what you want, but
here's some code I tried.
Basically, there are two interesting creation flags for CreateProcess:
CREATE_NEW_CONSOLE and DETACHED_PROCESS. The former opens a new DOS console for
a child process, the latter doesn't. DETACHED_PROCESS seems like what you want,
but I cannot make it write into the same console from where the parent process
launched.
The following is an example with modified win32_create_child_process from
popen.c. When you launch it, parent process prints "Hello from parent", creates
a child process and exits. Child continues running even if you close "DOS"
window. It will write "Hello, I'm a child process, writing #[number of write]"
to file C:\process-test.txt every second until you close it with Task manager.
#include <windows.h>
#include <fcntl.h>
#include <stdio.h>
static int win32_create_child_process(
char *zCmd, /* The command that the child process will run */
HANDLE hIn, /* Standard input */
HANDLE hOut, /* Standard output */
HANDLE hErr, /* Standard error */
DWORD *pChildPid /* OUT: Child process handle */
){
STARTUPINFO si;
PROCESS_INFORMATION pi;
BOOL rc;
memset(&si, 0, sizeof(si));
si.cb = sizeof(si);
si.dwFlags = STARTF_USESTDHANDLES;
SetHandleInformation(hIn, HANDLE_FLAG_INHERIT, TRUE);
si.hStdInput = hIn;
SetHandleInformation(hOut, HANDLE_FLAG_INHERIT, TRUE);
si.hStdOutput = hOut;
SetHandleInformation(hErr, HANDLE_FLAG_INHERIT, TRUE);
si.hStdError = hErr;
rc = CreateProcess(
NULL, /* Application Name */
zCmd, /* Command-line */
NULL, /* Process attributes */
NULL, /* Thread attributes */
TRUE, /* Inherit Handles */
DETACHED_PROCESS, /* Create flags */
NULL, /* Environment */
NULL, /* Current directory */
&si, /* Startup Info */
&pi /* Process Info */
);
if( rc ){
CloseHandle( pi.hProcess );
CloseHandle( pi.hThread );
*pChildPid = pi.dwProcessId;
}else{
//win32_fatal_error("cannot create child process");
printf("cannot create child process: %d", rc);
exit(0);
}
return rc!=0;
}
int main(int argc, const char *argv) {
if( argc > 1 ){
int i = 0;
for(;;){
FILE *f = fopen("C:\\process-test.txt", "a");
fprintf(f, "Hello, I'm a child process, writing #%d\n",
i++);
fclose(f);
Sleep(1000);
}
}else{
DWORD pChildPid;
printf("Hello from parent\n");
win32_create_child_process("a.exe child",
GetStdHandle(STD_INPUT_HANDLE),
GetStdHandle(STD_OUTPUT_HANDLE), GetStdHandle(STD_ERROR_HANDLE),
&pChildPid);
}
}
--
Dmitry Chestnykh
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