Function calls

Information on all of the MQI calls that are possible. Descriptions, syntax, parameter information, usage notes, and language invocations for each possible language are given for each of the different calls.

[AIX] [Linux] Online help on AIX® and Linux® platforms, in the form of man pages, is available for these calls.

Note: The calls associated with data conversion, MQXCNVC and MQ_DATA_CONV_EXIT, are described in Data-conversion exit.

Using the calls in the C language

Parameters that are input only and of type MQHCONN, MQHOBJ, MQHMSG, or MQLONG are passed by value. For all other parameters, the address of the parameter is passed by value.

You do not need to specify all parameters that are passed by address every time that you invoke a function. Where you do not need a particular parameter, specify a null pointer as the parameter on the function invocation, in place of the address of parameter data. Parameters for which this is possible are identified in the call descriptions.

No parameter is returned as the value of the call; in C terminology, this means that all calls return void.

Declaring the Buffer parameter

The MQGET, MQPUT, and MQPUT1 calls each have one parameter that has an undefined data type: the Buffer parameter. Use this parameter to send and receive the application's message data.

Parameters of this sort are shown in the C examples as arrays of MQBYTE. You can declare the parameters in this way, but it is usually more convenient to declare them as the particular structure that describes the layout of the data in the message. The function prototype declares the parameter as a pointer-to-void, so that you can specify the address of any sort of data as the parameter on the call invocation. Pointer-to-void is a pointer to data of undefined format. It is defined as:

typedef void *PMQVOID;