HP TACL User Manual

Requesting Nowaited Reads
Accessing Files
4–4 107365 Tandem Computers Incorporated
Requesting Nowaited
Reads
To open a file for nowaited read operations, issue a #REQUESTER call and omit the
WAIT option; for example, the following statement opens FILE1 and initializes
error_var, read_var, and prompt_var:
#SET rslt [#REQUESTER READ file1 error_var read_var
prompt_var]
Note It is very important to check the results of the open operation; otherwise, you will not know if the open
request received an error.
To specify shared, protected, or exclusive access to the file, use the EXCLUSION
option; the default for a read operation is shared. For example:
#REQUESTER /EXCLUSION PROTECTED/ READ file2 error_var &
read_var prompt_var
To initiate a read operation, append data to the prompt variable:
#APPEND prompt_var *start read*
To read a disk file, TACL discards the data in prompt_var, reads a record from
FILE1, and places it into read_var. You can use #EXTRACT(V) to retrieve data from
read_var; as you #EXTRACT records, TACL deletes them from read_var.
Each time you append a line to prompt_var, the TACL process reads a record from
disk file FILE1 and appends it to read_var. TACL then performs a READ operation.
TACL continues executing code; when you are ready to wait for completion of the
read operation, use the #WAIT built-in function to wait until read_var contains
data. To avoid writing over data that has not yet been transmitted, use #WAIT to
make sure the previous operation has finished.
When you are finished reading from the file, issue a CLOSE request and supply one of
the variables associated with the file; for example:
#REQUESTER CLOSE error_var
This operation closes FILE1 (associated with error_var) and terminates the
#REQUESTER function.
Use the routine in Figure 4-2, nowaited_read, to perform nowaited reads from the
file specified in the first argument in the invocation and display the records on the
terminal. To invoke this routine, load the file and type:
nowaited_read filename

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