Process Permanent Files (PPFs)

Four PPFs:

SYS$INPUT (UN*X equivalent: stdin)

SYS$OUTPUT (UN*X equivalent: stdout)
SYS$ERROR (UN*X equivalent: stderr)
SYS$COMMAND (no UN*X equivalent)

Starting with OpenVMS V7.2, the PIPE command adds:
SYS$PIPE (no UN*X equivalent)

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DCL has access to the Process Permanent Files or I/O streams associated with a process. Some of these have parallels in the UN*X and DOS/Windows worlds.

SYS$INPUT is equivalent to the UN*X standard input (stdin) stream.

SYS$OUTPUT is equivalent to the UN*X standard output (stdout) stream.

SYS$ERROR is equivalent to the UN*X standard error (stderr) stream.

SYS$COMMAND has no UN*X equivalent.

SYS$PIPE is present when using the PIPE command.