The PROGRAM_ENVIRONMENT environment variable is used in BS2000 to set whether file names or commands specified in the system() function call which have no BS2000 or POSIX prefix, are interpreted as BS2000 or POSIX files or commands.
At the BS2000 command level, PROGRAM_ENVIRONMENT is not set. For how to set environment variables, see section “Environment variables”.
When the POSIX shell is started, the PROGRAM_ENVIRONMENT variable is automatically set to the value SHELL, i.e. file names and commands which do not begin with "/BS2/" are interpreted as POSIX file names or commands.
File names or commands which do not comply with the syntax rules of the relevant environment are acknowledged with an error message.
If the specified file or command does not exist in the chosen environment, this is also reported with a message.
Explicit identification of file names as POSIX or BS2000
If the file name begins with a slash (/), it is interpreted as an absolute pathname of a POSIX file.
If the file name is specified in the format *POSIX(name), it is likewise interpreted as a POSIX file name.
If the file name begins with /BS2/, the file name which follows the /BS2/ is interpreted as a BS2000 file name.
Explicit identification of commands
If the command specified in the system() function call begins with /BS2/, the command which follows the /BS2/ is interpreted as a BS2000 command.
If the command is specified in the format *POSIX( command), it is interpreted as a POSIX command.