I'm using boost message_queue and I create the queue in one c++ program and use it in another program.
My problem is, that sometimes the first program doesn't run yet, but the second is running.
So when I start first program, I want to know, if the queue exists. I don't want to use message_queue::remove() because I don't want to lose some data.
The question is, how can I know if message_queue "bla_bla_queue" exists, or not?
message_queue q(open_only,"q");
According to the doc:
Opens a previously created process shared message queue with name "name". If the queue was not previously created or there are no free resources, throws an error.
So you should be able to catch an exception if the message queue does not exist.
A simple test_program showed me, that the interprocess_exception is thrown and the error code is 7, which indicates a not_found_error.
Create it and surround with try and catch. Read the doc to find the error code (for your specific version of boost) for already_exists (or something like that)
Check Boost 1.55 doc for an example in that version
Specifically, take a look at the linked code:
namespace boost {
namespace interprocess {
enum error_code_t { no_error = = 0, system_error, other_error,
security_error, read_only_error, io_error, path_error,
not_found_error, busy_error, already_exists_error,
not_empty_error, is_directory_error,
out_of_space_error, out_of_memory_error,
out_of_resource_error, lock_error, sem_error,
mode_error, size_error, corrupted_error,
not_such_file_or_directory, invalid_argument,
timeout_when_locking_error,
timeout_when_waiting_error };
typedef int native_error_t;
}
}
there is an
already_exists_error
already_exists_error". He wants to know, if the message queue does not exist :)