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| declaration/definition | no-default-io | ||||||||
Syntax
declare no-default-io
The no-default-io keyword prevents OmniMark from trying to
use standard input, standard output, or standard error, which are not
available to your program in certain environments. For example, you must
use no-default-io in OmniMark server programs and similar
transaction-based applications.
If you use no-default-io, you must include the instruction declare
no-default-io at the beginning of your program, before all other
program declarations except an escape declaration. The
escape declaration (if one is used) must be first.
If you use no-default-io, you must establish your own input
sources and output destinations.
Since no-default-io programs do not start with any established input sources or output destinations, the following streams cannot be used:
The #args shelf is still available in
no-default-io programs, but #main-input does not read data from
files named in that shelf as it would in a program without
no-default-io.
When using no-default-io, #current-output and
#current-input do not become available until explicitly connected
by the program, as shown in this example:
declare no-default-io
global stream in-file
global stream out-file
process
set in-file to file "inputfile"
open out-file as "outputfile"
using input as in-file
using output as out-file
submit #current-input
close out-file
#error is never available in a no-default-io
program, and all errors and status must be reported to an alternate
destination. OmniMark provides the log-message function
(part of the #builtin function library) as an alternate destination that
can be used in any program (with or without no-default-io).
You can test whether #current-input and
#current-output are available:
declare no-default-io
include "builtins.xin"
global stream in-file
global stream out-file
process
log-message "should not see in" when #current-input is attached
log-message "should not see out" when #current-output is attached
set in-file to file "inputfile"
open out-file as "outputfile"
using input as in-file
do
using output as out-file
do
log-message "should see in" when #current-input is attached
log-message "should see out" when #current-output is attached
submit #current-input
done
done
close out-file
log-message "should not see in" when #current-input is attached
log-message "should not see out" when #current-output is attached
A no-default-io declaration can only be used in process
programs. It cannot be used in aided translation type programs
(cross-translate, up-translate, down-translate, and context-translate).
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