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Not all commands display informational messages. Successful completion of a command is usually indicated when the DCL prompt returns. Unsuccessful completion is always indicated by one or more error messages.
If you enter a command incorrectly, the system displays a system message and prompts you for the correct command string, as the following example shows:
$ CAPY [Return] %DCL-W-IVVERB, unrecognized command verb - check validity and spelling \CAPY\ $
The format for the 3-part code is:
DCL-W-IVVERB
where:
| DCL | The OpenVMS facility or component name that returned the error. In this example, the message is from DCL, the default command interpreter. |
| W | A severity level that indicates a warning. Other severity levels include S (success), I (information), E (error), and F (fatal or severe error). |
| IVVERB | The type of message. The message can be identified by the mnemonic IVVERB in the OpenVMS system messages documentation or by using the Help Message utility (MSGHLP) described in Section 2.11.4. |
You can also receive system error messages during command execution if the system cannot perform the function you have requested. For example, if you type a PRINT command correctly but the file you specify does not exist, the PRINT command informs you of the error with a message like the following:
$ PRINT NOFILE.DAT [Return] %PRINT-E-OPENIN, error opening CLASS1:[MAYMON]NOFILE.DAT; as input -RMS-E-FNF, file not found $
The first message is from the PRINT command. It tells you it cannot open the specified file. The second message indicates the reason for the first; that is, the file cannot be found. RMS refers to the OpenVMS file-handling software, Record Management Services; error messages related to file-handling are generally OpenVMS RMS messages.
If you suspect that your process is not doing what you think it should be doing, press Ctrl/T. Ctrl/T displays a single line of statistical information about the current process. The statistical information includes node and user name, current time, current process, central processing unit (CPU) usage, number of page faults, level of I/O activity, and memory usage, which is listed in number of CPU-specific pages.
When you press Ctrl/T during an interactive terminal session, it momentarily interrupts the current command, command procedure, or image to display statistics. Although Ctrl/T disrupts the characters on the screen, it does not affect any procedure or editing session. For example, if a user named MCCARTHY on node GREEN presses Ctrl/T while using the EVE editor, the following line is displayed in the EVE message window:
GREEN::MCCARTHY 13:45:02 EVE CPU=00:00:03.33 PF=778 IO=295 MEM=315
To refresh the screen, press Ctrl/W.
Ctrl/T is disabled by default. If you know your system is running and Ctrl/T does not display statistical information, you can enable Ctrl/T with the DCL command SET CONTROL=T. Enter the command at DCL level (at the dollar sign ($) prompt), then press Ctrl/T again. Ctrl/T will remain in effect for the duration of your process, unless it is disabled from a program or command such as SET NOCONTROL=T. Note that your terminal must be set to BROADCAST mode for Ctrl/T to display on your screen. To set your terminal to BROADCAST mode, enter the DCL command SET TERMINAL/BROADCAST at the DCL prompt.
When you are logged in to the operating system, you can obtain information about using the system and available commands by using the HELP command. You can also get help on system messages by entering the HELP/MESSAGE command as shown in Section 2.11.4.
Use the following procedure to get help on OpenVMS commands and utilities:
| Step | Task |
|---|---|
| 1 |
Enter HELP at the DCL prompt and press Return.
HELP displays a list of topics and the Topic? prompt. |
| 2 | To see information about one of the topics, type the topic name after the prompt and press Return. |
| 3 |
If you want information on one of the subtopics, type the name after
the prompt and press Return.
HELP displays information about that subtopic. |
| 4 | To redisplay the SHOW USERS topic and the list of subtopics, enter a question mark (?) at the Subtopic? prompt. If you want to read all of the listed subtopics, enter an asterisk (*). |
| 5 | If you want information on another topic, press Return. Help displays the Topic? prompt. |
| 6 | To exit Help, press Return until you return to the DCL prompt. |
The following example shows the commands that you would enter to look for help about the SHOW USERS command:
$ HELP
HELP
.
. (HELP message text and subtopics)
.
Topic? SHOW USERS [Return]
SHOW
USERS
Displays the user name and node name (in a VAXcluster environment)
of interactive, subprocess, and batch users on the system.
Format
SHOW USERS [username]
Additional information available:
PARAMETER QUALIFIER
/BATCH /CLUSTER /FULL /INTERACTIVE /NETWORK /NODE
/OUTPUT /SUBPROCESS
Examples
SHOW USERS Subtopic? EXAMPLES
SHOW
USERS
Examples
.
. (SHOW USERS Examples message text and subtopics, if any)
.
SHOW USERS Subtopic? [Return]
SHOW Subtopic? [Return]
Topic? [Return]
$
If you know the command you need information about, enter HELP and the command name. For example, to get help about the SHOW USERS command enter the following command:
$ HELP SHOW USERS [Return]
If you need help but do not know what command or system topic to specify, enter the command HELP with the word HINTS as a parameter. Each task name listed in the HINTS text is associated with a list of related command names and system information topics.
The OpenVMS DCL Dictionary contains more information about the HELP command.
Use the Help Message utility (MSGHLP) to get online help for system messages. To display information on how the last command completed, type:
$ HELP/MESSAGE
You can also display information about a specific message by including the message identifier or words from the message text. For example:
$ HELP/MESSAGE BADACP
A message and its description can also be accessed by entering the message status code. For example:
$ HELP/MESSAGE/STATUS=%X00038090 [Return]If you do not know the message status code, you can view it by entering the command SHOW SYMBOL followed by the $STATUS global symbol. For example:
$ SHOW SYMBOL $STATUS $STATUS == "%X00038090"
The Help Message utility allows you to update the messages database with your own messages or to add comments to existing message descriptions. You can also extract a subset of messages from the messages database to create and print your own customized messages documentation. For details on how to use the Help Message utility, see OpenVMS System Messages: Companion Guide for Help Message UsersOpenVMS System Messages: Companion Guide for Help Message Users.
When you finish using the system, always log out. This prevents unauthorized users from accessing your account and the system. It is also a wise use of system resources; the resources you no longer need are available for other users.
To log out, enter LOGOUT at the DCL prompt. For example:
$ LOGOUT [Return]
The system displays a message, similar to the following message, confirming that you are logged out of the system:
$ LOGOUT [Return] HARRIS logged out at 11-DEC-1996 12:42:48.12
You can log out of the system only when you are at the DCL prompt ($). You cannot enter the LOGOUT command while you are compiling or executing a program, using a text editor (such as EDT or EVE), or running a utility (such as Mail). First you must exit the program, editor, or utility. When the system displays the DCL prompt, you can log out.
To find out how much time you spent at the terminal (elapsed time), how much computer time you used (charged CPU time), and other accounting information, enter LOGOUT/FULL at the DCL prompt. For example:
$ LOGOUT/FULL [Return]
The system displays information similar to the following:
SIMPSON logged out at 11-DEC-1996 12:42:48.12 Accounting information: Buffered I/O count: 8005 Peak working set size: 212 Direct I/O count: 504 Peak virtual size: 770 Page faults: 1476 Mounted volumes: 0 Charged CPU time:0 00:00:50.01 Elapsed time:0 02:27:43.06
You can end a remote session in two ways:
When you end a remote session, the system displays the message "%REM-S-END, control returned to node NODENAME::" and returns you to the process on the system from which you made the remote node connection.
If the network connection to a remote system is lost, DECnet will retransmit your data in an attempt to reestablish communications. If DECnet is unable to reestablish communications within a predetermined timeout period, your connection to the remote system is terminated and the system displays the message "Path lost to partner".
Logging out of a session conserves system resources and protects your files. Leaving a terminal on line represents one of the greatest sources of inside break-ins. When you leave your terminal on line and your office open, you have effectively given away your password and your privileges and have left your files and those of the other members of your group unprotected. Any user can easily and quickly transfer all files accessible through your account. A malicious insider could rename and delete your files and any other files to which you have write access. If you have special privileges, especially privileges in the Files or All category, a malicious user can do major damage.
Log out when you leave your office even for a brief period of time. If you have performed remote logins, you must log out of each node.
Clear your screen each time you log out of a terminal to ensure that your user name, node name, and operating system are not revealed to anyone else. If you are logging out after a remote login, the name of the node to which you return (the local node) is also revealed. If you access multiple accounts remotely over the network, the final sequence of logout commands reveals all the nodes and user names that are accessible to you on each node (excluding the name of the furthest node reached). To those who can recognize the operating system from the prompt or a logout message, these displays also reveal the operating system.
At some sites, it might be important to leave nothing but the logout message on your screen, as follows:
After the screen clears, the cursor is positioned at the top of the screen, next to the DCL prompt. Enter the DCL command LOGOUT at the prompt. The only information remaining after you log out is your logout command and the logout completion message. For example:
$ LOGOUT RDOGWOOD logged out at 11-DEC-1996 19:39:01.43
After you log out from a hardcopy terminal, remove, file, or dispose of all hardcopy output that might reveal sensitive information. Your security administrator should provide direction on preferred procedures. Many sites use paper shredders or locked receptacles for this purpose. Handle output that you plan to save just as carefully.
You should also dispose of hardcopy output if the system fails before you log out. In addition, if you will not be present when the system is initialized, turn your terminal off.
Your security administrator might ask you to break the connection to a dialup line when you log out. If you anticipate no further immediate use of the line, use the LOGOUT command with the /HANGUP qualifier. The /HANGUP qualifier directs the system to automatically break the connection to the dialup line after you log out.
Note
The effectiveness of the /HANGUP qualifier depends on how your system manager configures your modem line and how the line connects to the computer. It does not work on lines connected to a terminal server.
Breaking the connection to a dialup line:
This chapter describes how to use the DIGITAL Command Language. This chapter includes information on:
Complete information on all DCL commands, qualifiers, and parameters discussed in this chapter can be found in the OpenVMS DCL Dictionary and in online help.
The DIGITAL Command Language (DCL) is a set of English-like instructions that tell the operating system to perform specific operations.
DCL commands let you do the following:
To enter a DCL command, type the command at the DCL prompt ($) and press Return. DCL is not case sensitive; you can enter commands in either uppercase or lowercase letters.
In the following example, the DCL command SHOW TIME is entered as follows:
$ SHOW TIME [Return]
The system responds by displaying the current date and time and returns the DCL prompt to indicate it is ready to accept another command:
11-DEC-1996 15:41:43 $
The following table lists the DCL commands you use to perform a few common computing tasks:
| Command | Task |
|---|---|
| COPY | Makes a copy of a specified file |
| CREATE | Creates files or directories |
| DELETE | Erases a specified file and removes it from a directory |
| DIRECTORY | Displays the contents of a directory (list of files) |
| EDIT | Views and changes the contents of a text file |
| LOGOUT | Ends your session |
| Sends a specified file to a printer for printing | |
| RENAME | Changes the name or the location of a specified file |
| SET | Controls how you see the system on the screen |
| SHOW | Displays the status of the system |
| TYPE | Displays the contents of a specified file on the screen |
In addition to these DCL commands, you can perform tasks by using specific key sequences. A key sequence is a shortcut or a way to get the system's attention while it is processing another command.
To enter a key sequence, hold down the Ctrl key while you press and release a second key.
The following table describes a few commonly used key sequences. (Additional key sequences are listed in Section 3.12.)
| Key Sequence | Function |
|---|---|
| Ctrl/C | During command entry, cancels command processing. Ctrl/C displays on your screen as Cancel. |
| Ctrl/Y | Interrupts command processing. Ctrl/Y displays on your screen as Interrupt. |
| Ctrl/T | Displays information about the current process, unless the system is temporarily unresponsive or is set to NOBROADCAST. For more information on using Ctrl/T, see Section 2.10. |
Like a spoken language, DCL is made up of words (vocabulary) and word order (syntax or format). The following sections describe these two elements and explain how to construct a valid DCL command.
The following example shows the general format and parts of a DCL command line:
$ PRINT/COPIES = 5 GROCERY.LIS [Return] (1) (2) (3) (4) (5) (6)
The following list describes each element of the DCL command line:
The following items may also be used in a DCL command line:
Just as a spoken language depends on the order of words to create meaning, DCL requires that you put the correct elements of the command line in a specific word order or format.
Following are two examples of the syntax, or format, used for typical DCL commands:
command/qualifier=value=keyword
command parameter/qualifier
When you enter a DCL command, some parameters are required; they must be entered on the command line. If you do not enter them, the system prompts you to supply the missing information. A line beginning with an underscore (_) means that the system is waiting for your response.
When you are prompted for an optional parameter, press Return to omit it. At any prompt, after you enter the required parameter, you can enter one or more of the remaining parameters and any additional qualifiers.
Note that you must enclose in quotation marks ("") any parameter containing a slash (/) or at sign (@).
In the following example, the TYPE command requires a file specification. Because a file specification is a required parameter of the TYPE command, if you do not enter one, the system requests it.
$ TYPE _File: WATER.TXT
If you press Ctrl/Z after a command prompt, DCL ignores the command and redisplays the DCL prompt.
Some items, called defaults, need not be specified on the command line. When DCL performs an operation by default, it assigns a command certain values or performs certain functions associated with that command even though you may not have explicitly specified those values or functions when you entered the command. In general, the values and functions are those considered typical or expected by users.
DCL supplies default values in several areas, including command parameters and qualifiers. Parameter defaults are described in the following section. Qualifier defaults are described in Section 3.7.
If the number of copies is not specified as a qualifier for the PRINT command, DCL uses the default value 1. In the following example, the default is overridden and multiple copies of the file are printed by including the /COPIES qualifier on the PRINT command line:
$ PRINT/COPIES=4 MYFILE.TXT
If you enter a command longer than one line, you can continue the command onto the next line by following this procedure:
| Step | Task |
|---|---|
| 1 |
End the command line with a hyphen (-) and press Return.
The system displays an underscore (_) followed by the DCL prompt ($). |
| 2 |
Enter the rest of the command line after this prompt.
A line beginning with an underscore means that the system is waiting for your response. |
6489P003.HTM OSSG Documentation 22-NOV-1996 13:16:35.12
Copyright © Digital Equipment Corporation 1996. All Rights Reserved.