Re: g_spawn and files left locked on windows.

[Richard Shann <richard shann virgin net>]

Thank you for your observations.
On Tue, 2009-04-28 at 07:45 -0700, Ardhan Madras wrote:
> As far i know in win32, if a process is opening a new file, then normally another process couldn't write or 
> remove it.
yes that's right.
>  It's maybe a synchronization method offered by win32 by automatically locking a file descriptor. Linux 
> doesn't automatically provide such a file locking mechanism to a file opened by a process.
>
> So if the file left locked, there are must be a process which still open the file or a file is still left 
> opened. Win32 maybe doesn't automatically release such as opened file's resources.
The process had finished, and that was why I was puzzled.
> In your project or demonstration code: I see you don't fclose() your file before exit 
I *do* fclose() the file in the program that creates it (i.e. in the
program "doit"). It is also guaranteed to be closed by the main of that
program returning, that is as part of the exit. The other program is
just finding out if the file is locked by trying to open it, so it
doesn't matter what it does with it. The test does, in fact work
pefectly on both platforms, so my problem lay elsewhere.
Richard

> (actually i don't know if this have the 'locking effect'), and you may interest using a GIOChannel for file 
> operations.
>
> --- ajhwb
>
>
> --- richard shann virgin net wrote:
>
> From: Richard Shann <richard shann virgin net>
> To: gtk-app-devel-list gnome org
> Subject: Re: g_spawn and files left locked on windows.
> Date: Tue, 28 Apr 2009 08:39:12 +0100
>
> On Mon, 2009-04-27 at 12:52 +0300, Tor Lillqvist wrote:
> > > My application invokes the lilypond program using the g_spawn...
> > > functions. This works fine on linux, but on windows the files created by
> > > lilypond are left locked when lilypond has exited.
> >
> > That sounds very odd and in fact impossible. Are you confusing file
> > protection with locking?
> Thank you for the quick and helpful reply. Having contstructed the
> minimal example, everything worked fine. 
> For those listening in who need to create a glib standalone minimal
> example. I append the code I devised.
> Richard
> /************ first program, invoked by the one below *************/
> #include <stdio.h>
>
> /*
> program doit
>  gcc test.c -o doit.exe
> */
> int main(void) {
>   printf("Opening the test file now\n");
>   FILE *fp = fopen("thetestfile","w");
>   if(fp==NULL) {
>   printf("doit could not open the test file");
>   return -1;
>   }
>   printf("Writing to the test file now\n");
>   fprintf(fp, "hello");
>   fclose(fp);
>   return 0;
> }
>
> /****************** second program, invoking the first *********************/
>
> /*
> program test
>  gcc  test.c -o test.exe -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include  /usr/lib/libglib-2.0.so
> */
> #include <stdio.h>
> #include <glib.h>
> static GPid pid = -1;
> void finished(void) {
>   g_spawn_close_pid (pid);
>   FILE *fp = fopen("thetestfile","rw");
>   if(fp==NULL) {
>     g_print("could not open\n");
>     exit(-1);
>   }
>   g_print("The file opens ok\n");
>   exit(0);
> }
>
> int main(void) {
>   g_print("Starting the test\n");
>   gchar *arguments[] = {
>     "doit.exe",
>     NULL
>   };
>   g_spawn_async_with_pipes (NULL,               /* dir */
>                 arguments, NULL,        /* env */
>                 G_SPAWN_SEARCH_PATH  | G_SPAWN_DO_NOT_REAP_CHILD, NULL, /* child setup func */
>                 NULL,           /* user data */
>                 &pid,
>                 NULL,
>                 NULL,           /* stdout */
>                 NULL,           /* stderr */
>                 NULL);
>  g_child_watch_add (pid, (GChildWatchFunc)finished, NULL);
>  g_print("looping for ever, Ctrl-C to kill\n");
>  GMainLoop* gm = g_main_loop_new(NULL, 0);
>  g_main_loop_run(gm);
> }
>
>
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