intro_to_the_dcl_command_line

This is an old revision of the document!


Intro to DCL

DCL is the “Digital Command Language”, and is equivalent in intent to a command-line shell, like bash or zsh, in Linux and Unix – in short, DCL is the VMS command-line shell. You (the VMS user) can enter DCL commands to perform file management, program development, system administration and other tasks as needed.

The basic DCL command looks like this:

$ COMMAND-VERB [/QUALIFIER] [param1] [param2]... [/QUALIFIER]

where:

  • COMMAND-VERB is a command (verb) which performs some specific action.
  • Any command element enclosed in square-brackets [ ] is optional.
  • /QUALIFIER is a command-specific modifier (adverb) for that action.
  • param1, param2, are parameters or arguments which are operated on by the command (verb). Any particular command can have zero, one, two or several arguments.

Other things to know about DCL commands:

  • Command lines can be entered in UPPER, lower and/or Mixed-case.
  • As DCL actually parses (processes) a command (when you hit the Enter key), it UP-CASES all command text (unless the text is enclosed in double-quote marks), and compresses any/all multiple runs of space (blank) and tab characters to a single space.
  • Command lines can be edited using “typical” editing keys, including left- and right-arrows (to move the cursor), the Backspace key (to erase characters), Ctrl/A to toggle between insert and overstrike entry modes, Ctrl/U to erase the entire command to left of current cursor, and more.
  • Command short-cuts (same as “aliases” in bash and other shells) can be created for user's convenience.
  • DCL supports and recognizes logical names and symbols (or variables) in-context as it parses and executes commands.

When DCL executes a command, one of two things can happen:

  1. The command executes completely and without errors, and does what you said/intended. Successful commands typically “complete silently,” that is, without generating any error text on-screen.
  2. The command encounters one or more situations which cause error(s), and the command likely terminates, partially completes, or completes with warnings. In this situation, explanatory error messages are produced on your terminal screen. In most cases, the error message(s) will help you determine the cause of the problem, and may suggest specific actions you can take to fix it.
intro_to_the_dcl_command_line.1538599823.txt.gz · Last modified: 2018/10/03 20:50 by lricker