Technical data

Managing User Accounts
7.8 Restricting the Use of Accounts
Example 7–4 Sample Captive Command Procedure
$ deassign sys$input
$ previous_sysinput == f$logical("SYS$INPUT")
$ on error then goto next_command
$ on control_y then goto next_command
$ set control=(y,t)
$
$next_command:
$ on error then goto next_command
$ on control_y then goto next_command
$
$ if previous_sysinput .nes. f$logical("SYS$INPUT") then deassign sys$input
$ read/end=next_command/prompt="$ " sys$command command
$ command == f$edit(command,"UPCASE,TRIM,COMPRESS")
$ if f$length(command) .eq. 0 then goto next_command
$
$ delete = "delete"
$ delete/symbol/local/all
$ if f$locate("@",command) .ne. f$length(command) then goto illegal_command
$ if f$locate("=",command) .ne. f$length(command) then goto illegal_command
$ if f$locate("F$",command) .ne. f$length(command) then goto illegal_command
$ verb = f$element(0," ",command)
$
$ if verb .EQS. "LOGOUT" then goto do_logout
$ if verb .EQS. "HELP" then goto do_help
$
$ write sys$output "%CAPTIVE-W-IVVERB, unrecognized command \",verb,"\"
$ goto next_command
$
$illegal_command:
$ write sys$output "%CAPTIVE-W-ILLEGAL, bad characters in command line"
$ goto next_command
$
$do_logout:
$ logout
$ goto next_command
$
$do_help:
$ define sys$input sys$command
$ help
$ goto next_command
7.8.6 Setting Priorities for User Processes
A user’s priority is the base priority used in scheduling the process that the
system creates for the user.
On VAX systems, priorities range in value from a low of 0 to a high of 31; 0
through 15 are timesharing priorities; 16 through 31 are real-time priorities.
On Alpha systems, priorities range in value from a low of 0 to a high of 63; 0
through 15 are timesharing priorities; 16 through 63 are real-time priorities.
Processes with real-time priorities are scheduled strictly according to base
priority; in other words, the executable real-time process with the highest base
priority is executed first. Processes with timesharing priorities are scheduled
according to a slightly different principle to promote overlapping of computation
and I/O activities.
Managing User Accounts 7–33