Open System Services Porting Guide (G06.24+, H06.03+)

Migrating Guardian Applications to the OSS
Environment
Open System Services Porting Guide—520573-006
8-20
Using Intermediate Processes
resource allocation usage. OSS semaphores are available only to OSS programs.
Semaphores are commonly used in both the OSS environment and the Guardian
environment to synchronize access to shared memory. When memory is shared
between a Guardian process and an OSS process, Guardian semaphores must be
used.
Using Intermediate Processes
The osh and gtacl commands are provided as intermediate, or bridge, processes
between the Guardian and OSS environments. They can be used to map I/O,
particularly terminal I/O, into the opposite type, and to map death notifications into the
opposite type. The osh and gtacl commands can be used programmatically as well
as commands to the TACL and shell command interpreters, respectively.
From an OSS process, you can use the popen() function to programmatically call a
TACL command. For example, popen("gtacl -p FUP","w") can be used to pipe
commands through gtacl to FUP.
The gtacl command can also be used directly from the shell to pass commands to a
TACL command and redirect the output to a file in the OSS file system: for example,
"gtacl -p 'FUP INFO $SYSTEM.*.* '> tempfile".
The OSH command can be used directly from the TACL prompt to pass commands to
the shell, even redirecting output to a file in the Guardian file system. Because OSH
and gtacl are intermediate processes, they are expensive to create, and expensive to
use for I/O between the Guardian and OSS environments.
Using Signals
OSS processes can send and receive signals; Guardian TNS processes cannot send
signals. Guardian processes can generate signals by using kill(), but they cannot
receive them. Neither TNS nor native processes can send or receive signals using
kill(). Thus, a Guardian process can call kill() for an OSS process (or group). It
needs to find the OSS process ID of the OSS process to do this, possibly using
PROCESS_GETINFO_. Signals can be used to communicate small bits of information
from a Guardian process to an OSS process, but they are not a general-purpose IPC
mechanism that should be used when Guardian and OSS processes need to
communicate.
Starting an OSS Program From the Guardian
Environment
Migration from the Guardian environment to the OSS environment can involve the
ability to start an OSS program from the Guardian environment, which you can do
either using commands or programmatically, as described in the following subsections:
•
Using OSH From TACL on page 8-21
•
Using system() in a Guardian Program on page 8-21