COBOL Manual for TNS and TNS/R Programs

Printer and Spooler Output
HP COBOL Manual for TNS and TNS/R Programs—522555-006
30-22
Logging Program Activity Information to a Printer
Logging Program Activity Information to a
Printer
To record a log of program activity to a printer, you can use either of these statements:
•
DISPLAY
•
WRITE (usually preferable)
DISPLAY
If you use the DISPLAY statement to send messages to a printer for shared access,
you must associate a mnemonic name with the printer device name (such as $LP) in
the SPECIAL-NAMES paragraph. This association is established at compilation time.
Each DISPLAY statement transmits characters to a single device—there is no
mechanism for changing the destination of a DISPLAY statement.
Every time your process executes a DISPLAY statement, it must open the printer, write
one line of characters, and close the printer. The printer is then available to other
processes until the next time your process executes a DISPLAY statement. You cannot
use the DISPLAY statement to deliver characters to a spooler.
In the OSS environment, if a DISPLAY statement includes mnemonic-name, it must
be either the OSS pathname of a Guardian file or the name of an OSS text file.
WRITE
If you use the WRITE statement to send messages to a printer, you can determine the
assignment between the file and the device:
•
At compilation through the SELECT clause of the FILE-CONTROL paragraph
•
At the beginning of execution with the TACL command ASSIGN or ADD DEFINE
(in the Guardian environment only)
•
During execution through the invocation of the routine COBOLASSIGN (in the non-
CRE environment) or the routine COBOL_ASSIGN_ (in the CRE)
The WRITE statement has these advantages over the DISPLAY statement:
•
If there are several printers and the one you expected to use is busy, you can
redirect the file to another printer.
•
You can open the file for exclusive access (the default exclusion mode for printers)
and be certain that no other process can send characters to the device while you
are using it.
•
You can recover from input-output errors by using declaratives.
•
You can use the PARAM PRINTER-CONTROL command to handle the condition
of the printer’s being out of paper (in the Guardian environment only).