SYS$INPUT

SYS$INPUT is a process-permanent logical name that denotes the default file or device from which DCL reads input.

Default

In an interactive process, the default value of SYS$INPUT is the terminal. In a command procedure run interactively, the default value of SYS$INPUT is the command procedure file. In a command procedure run as a batch job, the default value of SYS$INPUT is the command procedure file.

Usage

If you specify SYS$INPUT as the file specification for a command, you are prompted for the text while still remaining at the DCL level. For example:

$ mail sys$input jdoe
Enter your message below. Press CTRL/Z when complete, or CTRL/C to quit:
hi there
 Exit
New mail from JDOE
$
 

You can also redefine SYS$INPUT so that an image, invoked by a command procedure, reads input from the terminal or another file. Because DCL always obtains input from the default input stream, DCL ignores a redefinition of SYS$INPUT. The OpenVMS Help Facility offers the following example of an input file for the SORT command:

! PEOPLE.DAT
! A set of data with embedded key qualifiers for the SORT command.
!
! Usage: SORT@PEOPLE.DAT
!
/KEY=(POS:10,SIZE:10) sys$input people.out
Fred     Flintstone    555-1234
Barney   Rubble        555-2244
Wilma    Flintstone    555-1234
Betty    Rubble        555-2244
George   Slate         555-8911
Dino     Dinosaur      555-1234
 

Calling SORT@PEOPLE.DAT would therefore produce PEOPLE.OUT that would contain the table above sorted by surname.

Displaying

The current value of SYS$INPUT can be displayed with the SHOW LOGICAL command. It displays only the device portion of the string. In the example below, SYS$INPUT is defined to a file:

  "SYS$INPUT" = "_DSA0:" (LNM$PROCESS_TABLE)

In the example below, SYS$INPUT is defined to a terminal:

  "SYS$INPUT" = "_TNA18:" (LNM$PROCESS_TABLE)

Redefining

SYS$INPUT can be redefined so that an image takes its input from wherever it is redefined to. Most commands, except for those executed inside DCL, invoke images. Because DCL always obtains input from the default input stream, DCL ignores a redefinition of SYS$INPUT. In the following example, SYS$INPUT is redefined to SYS$COMMAND (the terminal) so that the image invoked with the next command (TPU) would use the terminal and not the command procedure file as a source of input.

$ DEFINE/USER_MODE SYS$INPUT SYS$COMMAND
$ EDIT/TPU MYFILE.DAT
.
.
.
 

When the image is finished, SYS$INPUT resumes with the default input stream (the command file).