Frame definition files

Using co-processing utilities

Co-processing allows an external process to communicate with the user via a menu, form, or text frame. A co-process does not have direct access to the terminal's screen. It communicates with the FMLI application, which can then post the messages in the frame that contains the co-processing descriptors or take other appropriate actions.

The co-processing feature in FMLI consists of five built-in utilities: cocreate, cosend, cocheck, coreceive, and codestroy, which support interprocess communication.

The cocreate utility is responsible for initializing the co-process and setting up pipes between it and FMLI. The codestroy utility is responsible for cleaning up when the communication has been completed. The utility cosend is used to send information to the co-process via the pipe and block (wait) for some response by the co-process. The -n option to cosend performs a ``no wait'' write. This means that cosend will send information to the co-process but will not block for a response. The cocheck utility checks the incoming pipe for information. The coreceive utility performs a ``no-wait'' read on the pipe. The purpose of these built-in utilities is to provide a flexible means of interaction between FMLI and a co-process; to be responsive to asynchronous activity.

It is important to note that information passed to FMLI from a co-process is treated as text only. FMLI commands (for example, open, close, update) will not be recognized by FMLI unless they become the value of a descriptor of type command.

To illustrate the use of co-processing, consider a UNIX system program that wishes to ``talk'' to the user as it executes (an interactive program). The following sample menu displays the item talk. When talk is selected, the backquoted expression creates the co-process and then opens an ``interactive'' form,

   menu="My Menu"
   action=`cocreate -i MYPROC talk` open an example of co-processing

In the form frame definition file, shown in `` an example of co-processing'', the following occurs:

   form="Talking ..."
   close=`codestroy MYPROC`
   reread=`cocheck MYPROC`

name="" fcol=0 rows=5 columns=20 inactive value="`coreceive MYPROC`"

name="" fcol=0 columns=20 valid=`cosend -n MYPROC "$F2"`TRUE

name=abort button=8 action=`message "Communication stopped ..."`close an example of co-processing

The following code segment illustrates how an interactive co-process (in this case talk) may be structured:

   while :
   echo "I received $response."
      read response
      if [ "$response" = "goodbye" ]
   echo "goodbye"

talk: an example of a co-process

The executable vsig(1fmli) is used to send a signal telling the interpreter that information is pending. This interrupt causes reread to be evaluated. For more information about co-processing, see the coproc(1fmli) manual page.

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UnixWare 7 Release 7.1.4 - 27 April 2004