How do I check for the existence of a named resource in using boost

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interprocess without wrapping a open_only in a try catch block and waiting for the exception?

That's the only way.

Well you know that they say.... if first you don't succeed try... catch again. I sure hope that this is not standard coding practices for Boost.Interprocess. I have seen this before in the likes of Borland Builder (VCL) and Java and I consider this to be poor programming practices. I realize that boost is working to create a standard library to mirror the likes of Java... I just hope Boost does not mirror(copy) the bad practices as well. I hope this gets fixed in future releases. The logic here is to see if a named mutex is in existence (checking to see if process is running) if not launch the app that will create it (auto launch the app). Then take the mutex and do some stuff then release. This results in a try.. catch... fail.. try ... catch succeed. I have tested this and it works however sloppy it may be. Strange how objects created with in a shared memory region can be searched for, but not the shared memroy region itself or named mutexes. --snip from boost.interporcess documentatoin-- //Find the array res = segment.find<MyType> ("MyType array"); --end snip--

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I'll add this to my to-do list. What would be your proposal? Should we take in care also permission or mode (r/w) issues?

Currently I just need to know if the named objects exist in shared memory. Well after having looked through the documentation and trying to get to know the API a little lately. I would like to see some things. 1) Provide the use of std::system to launching processes maybe boost::inter process::system(...) to allow spawning a process in a non blocking fashion. as the following code in Windows allows (on Linux I think & would work after the command using std::system though I have not tried this): Currently what I am using on windows: <code> std::string path = getenv( "PATH" ); path = "PATH=" + path; std::cout << "The current path is " << path << std::endl; char *pValue; size_t len; errno_t err = _dupenv_s( &pValue, &len, "path" ); path = pValue; std::cout << "The current path is " << path << std::endl; mexPrintf( "The current path is %s", path.c_str() ); if( 0 == _spawnlp( _P_DETACH, "cmd", "cmd", "/K", "dsa4DTool.exe", NULL) ) { printf( "dsa4DTool lanuched sucessfully\n" ); } else { printf( "dsa4DTool failed to launch\n" ); } </code> 2) As discussed provide ability to search for every named shared memory variable. Currently I was having problems with the code where I try to search for a shared memory variable that may have, but not necessarily have, already been created by the process running the code in the previous run of the process. This may be working, but I have not had success with it yet. The first call : res = segment.find ("show_volume_data_dimensions"); seems to block indefinitely in the code if the named object does not exist yet. The logic was open the shared memory region using open and check if the show_volume_data_dimensions_t object exists (the process has run one time before) if not created it (this is the first time the process is running). It appears that using CreateFileMapping will set ERROR_ALREADY_EXISTS which can be determined from GetLastError after the call (attempt to open the shared memory region) to CreateFileMapping. Then if the file did not exist and was created CloseHandle could be called. Of course then comes the problem of inter-process race conditions. It does not appear that FindFirstFileEx supports named files. Though this still does not preclude interprocess from not throwing a exceptoin as boost.filesystem filebuf.open does not seem to throw on failed open and fb.is_open() can be called along with fb::exists(p) syntax from: http://live.boost.org/doc/libs/1_41_0/libs/filesystem/test/fstream_test.cpp So I guess my proposal would be to mirror the likes of boost.filesystem <code> try{ //shared_memory_object::remove("show_volume_data"); managed_shared_memory segment //create segment name segment size (open_or_create, "show_volume_data", sizeof(show_volume_data_dimensions_t) ); show_volume_data_dimensions_t * vol_dimensions = NULL; std::pair res; std::cout << "attempting to open named shared memory region: show_volume_data_dimensions" << std::endl; res = segment.find ("show_volume_data_dimensions"); if( res.second < 1 ) { try { std::cout << "shared memory region was not found" << std::endl; std::cout << "attempting to create shared memory region" << std::endl; vol_dimensions = segment.construct ("show_volume_data_dimensions") //name of the object ()/*(x_dim, y_dim, z_dim)*/; //ctor first argument } catch( ... ) { } } else { vol_dimensions = res.first; } std::cout << "setting volume data\n"; vol_dimensions->x_dim = x_dim; vol_dimensions->y_dim = y_dim; vol_dimensions->z_dim = z_dim; std::cout << str( boost::format( "dimensions of data are:\n" "x_dim = %d, y_dim = %d, z_dim = %d\n" ) % vol_dimensions->x_dim % vol_dimensions->y_dim % vol_dimensions->z_dim ); } catch( boost::interprocess::interprocess_exception e ) { std::cout << "exception: " << e.what(); shared_memory_object::remove("show_volume_data"); throw; } catch( ... ) { std::cout << "unknown exception occured\n"; shared_memory_object::remove("show_volume_data"); throw; } // shared_memory_object::remove("show_volume_data"); </code>