HP TACL User Manual

Using INV and OUTV
Initiating and Communicating With Processes
5–16 107365 Tandem Computers Incorporated
Generating Commands
Because data transfer occurs through variables, be careful when moving data to and
from the variables. For example, when a process is running in the nowait mode, it is
possible to attempt an operation before the preceding operation has finished.
Caution Data can be unexpectedly lost or duplicated during data transfer. To avoid lost or duplicated data, follow
these guidelines.
Use #APPEND or #APPENDV to manage IN variables. Each of these functions
appends a line to a variable level in such a way that no data is lost or removed. Do
not expect to examine data you have put into an IN variable—the data can be sent
as soon as you append it to the variable. (If you use #SET instead of #APPEND to
manage IN variables, queued lines in the IN variable can be lost before they are
sent.)
Use #EXTRACT or #EXTRACTV to manage OUT variables. Each of these
functions removes the first line from a variable level in such a way that no data is
lost if the process is simultaneously adding lines to a variable level. If you use
#OUTPUTV to display an OUT variable and then use #SET to clear it, a new line
could arrive between the #OUTPUT and the #SET; that line would be lost.
Use #WAIT to delay processing until one of a list of variable levels is ready.
#WAIT returns the fully qualified name of that variable level.
The OUT and PROMPT variables are ready if they have data in them.
An IN variable is ready if it is empty and a process is waiting for you to put
data into it.
A STATUS variable is ready if its process was deleted.
Any other variable is always ready.
Use #EOF to cause an end-of-file on an IN variable. If the IN variable is empty
and a process is waiting, an end-of-file is immediately sent to the process. If the
IN variable is empty and a process is not waiting, a flag is set. The next time the
process attempts to read from the empty IN variable, TACL sends an EOF and the
flag is cleared. #EOF does not alter the state of the process or the IN variable, but
it can cause the process to terminate.
The following examples illustrate the use of INV and OUTV.

HP TACL Specifications

General

Name	HP TACL
Purpose	Task automation, system management, and application control
Category	Software
Platform	HP NonStop
Type	Scripting language
Developer	Hewlett-Packard

Summary

Section 1 An Overview of TACL

Running the Examples in This Manual

Instructions for executing manual examples, including setting required variables.

About This Manual

Section 2 Developing TACL Programs

Processing Character Data

Covers tasks like constructing text strings, analyzing output, and manipulating characters.

Debugging TACL Programs

Introduces the TACL debugger for step-by-step execution and variable examination.

Section 3 Developing TACL Routines

Processing Arguments

Details how routines handle arguments using #ARGUMENT, including options and alternatives.

Writing an Exception Handler

Explains handling events like BREAK keys or TACL errors using exception handlers.

4 Accessing Files

#REQUESTER Operation

Describes the #REQUESTER function for opening files and initiating I/O operations.

Requesting Waited Reads

Explains opening files for waited read operations using #REQUESTER.

5 Initiating and Communicating With Processes

Initiating a Process: RUN and #NEWPROCESS

Covers starting processes using RUN and #NEWPROCESS, including startup options.

Using the INLINE Facility

Using INV and OUTV

Using $RECEIVE

Using #SERVER

6 Running TACL as a Server

Running a TACL Process as a Server

Explains making a TACL process a server by establishing its IN file as $RECEIVE.

Running TACL Code as a Server

Details providing TACL code for a TACL-server process using #INPUTV and #REPLYV.

Using TACL as a Pathway Server

Describes creating a Pathway environment with TCP and TACL servers to process requests.

7 Using Programmatic Interfaces

Overview of SPI and EMS

Using SPI

Using EMS

8 Example of a System Management Program

Monitoring System Operation