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

Migrating Guardian Applications to the OSS
Environment
Open System Services Porting Guide—520573-006
8-22
Using PROCESS_SPAWN_ in a Guardian Program
Using PROCESS_SPAWN_ in a Guardian Program
Another way to start OSS programs from the Guardian environment is to use the
PROCESS_SPAWN_ procedure call in a Guardian program from the TACL command
interpreter. This method is a much more direct means of starting an OSS process from
the Guardian environment, because the OSS shell command interpreter is not
involved.
A new OSS process is created optionally with an assigned name, with the caller
becoming the Guardian parent of the OSS child process. The caller will be notified of
child process termination through a system message on $RECEIVE, not through an
OSS SIGCHLD signal.
DEFINEs can be propagated to the new process. OSS processes can be created in a
waited or nowait manner. The files to be opened in the new process must be specified
in a file descriptor structure that is passed as an argument to the call. Certain
inheritance features and process attributes can be specified for the OSS process
created. An example of how this Guardian procedure can be used to start up an OSS
process from the Guardian environment is shown in the Open System Services
Programmer’s Guide.
Another benefit of using PROCESS_SPAWN_ to create an OSS process from the
Guardian environment is that when the calling process is a Guardian monitor process
pair, the monitor can ensure that an OSS child process is restarted if it stops. The OSS
child process can be considered to be a persistent process in this case. Because the
PROCESS_SPAWN_ procedure can be used to create an OSS process in a nowait
manner, the calling process can continue processing while the child process is being
created. More information on managing OSS processes from the Guardian
environment is available in the Open System Services Programmer’s Guide.