[Info-vax] %PCSIUI-E-PRIVCLASS1 when using PRODUCT with PIPE

[Stephen Hoffman]

On 2018-12-07 17:31:48 +0000, Jairo Alves said:

> $ @TT:/OUTPUT=file
> $ {command}
> ^Z
> 
> That works(!) even without granting an extra privilege, which is a bonus.

It works?  Oh, my.  How odd.

> How does it do it, though?

That is a DCL command procedure invocation.  That command procedure 
specifies the input be from the TT device.  That then creates the DCL 
equivalent of a subshell.  And the output from DCL procedure 
invocations can be redirected.

> What do the TT stands for?

TT: is the command input device.  It's an RSX-era device naming 
construct, and is a shorthand name for the current terminal or terminal 
emulation session.

The OpenVMS logical names SYS$INPUT, SYS$COMMAND, SYS$OUTPUT and 
SYS$PIPE have some similar uses, and can also be useful for redirection 
and for pipelines.

> Why the Ctrl+Z at the end?

That's the End Of File for the input into that DCL procedure 
invocation.  You're effectively writing a DCL command procedure 
directly into the DCL interpreter, and the ^Z pops the equivalent of a 
subshell and returns you to the interactive DCL prompt.

The syntax in this area is also related to the leading $ sign in DCL 
procedures for commands and no leading $ for data, and the DECK command.

This area also has parallels to the SYSBOOT> SET/STARTUP=OPA0: 
conversational environment; the OpenVMS analog to the Unix single-user 
mode environment.  In that context, you're effectively entering the 
commands of the startup script.

DCL pipelines and DCL I/O redirection are all still somewhat of a tire 
fire, unfortunately.

-- 
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