Open System Services Programmer's Guide

The value specified for input can be either of the following:
• A Guardian process; for example, $vhs (Guardian virtual hometerm subsystem) or $zhome
(Guardian reliable home terminal).
• Any Telserv terminal.
The OSSTTY process will redirect all data received from the specified input to any process that
uses $process-name.#stdin (Guardian process) or /G/process-name/#stdin (OSS
process) as its standard input.
The value specified for output can be any of the following:
• A Guardian process; for example, $vhs (Guardian virtual hometerm subsystem) or $zhome
(Guardian reliable home terminal).
• Any Telserv terminal.
• A Guardian EDIT file.
OSSTTY will redirect to the specified output all data received from any process that uses
$process-name.#stdout (Guardian process) or /G/process-name/#stdout (OSS process)
as its standard output.
The value specified for hometerm can be either of the following:
• A Guardian process; for example, $vhs (Guardian virtual hometerm subsystem) or $zhome
(Guardian reliable home terminal).
• Any Telserv terminal.
OSSTTY will redirect to the specified hometerm all error messages received from any process that
uses $process-name.#stderr (Guardian process) or /G/process-name/#stderr (OSS
process) as its standard error.
Starting OSSTTY on the OSH Command Line
You can start OSSTTY by specifying the -osstty flag on the osh command line. The osh command
initially routes the input, output, and error file information of the OSS process it launches to its own
standard input, output, and error files. You can specify standard input, output, and error files for
the child process on the osh command as run options or by using the redirection operators (<, >,
2>); for example:
TACL> osh/ in input, out output, term hometerm/ -osstty
TACL> osh -osstty > output
The values for input, output, and hometerm are as described under “Starting OSSTTY From
the TACL Prompt”.
When -osstty is specified on the osh command line, OSSTTY is launched only if the OSS shell
determines that it is necessary. The OSS shell makes this determination based on the standard files
specified in the run options or through redirection operators: if any one of the files specified is not
accessible to the child process, then OSSTTY is launched. For example, in the following command,
OSSTTY is launched because OSS cannot access the Guardian EDIT file myfile as an output file:
TACL> osh/out $data.mysubvol.myfile/ -osstty
If the files specified as run options or through redirection operators are accessible to OSS, then
OSSTTY is not launched. For example, the following command does not launch OSSTTY because
Guardian EDIT files are accessible to OSS processes as input:
TACL> osh/ in $data.mysubvol.myfile/ -osstty
Once started, OSSTTY becomes the standard input, standard output, and standard error of the
OSS process, and redirects input, output, and error data to the Guardian targets specified as run
options or through redirection operators.
216 Managing I/O