|Document revision date: 15 July 2002|
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:
The system displays a message, similar to the following message, confirming that you are logged out of the system:
$ LOGOUT HARRIS logged out at 11-DEC-2002 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
1.12.1 Obtaining Accounting Information
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:
The system displays information similar to the following:
SIMPSON logged out at 11-DEC-2002 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 Entered to node NODENAME::" and Enters
you to the process on the system from which you made the remote node
1.12.3 Lost Network Connections
If a TCP/IP network connection to a remote system is lost, TCP/IP uses
the best-effort delivery protocol, which is a
characteristic of network technologies that attempts to deliver data
but does not try to recover if there is an error such as a line failure.
If a DECnet 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."
1.13 Logging Out Without Compromising System Security
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.
If you are working on a system that doesn't automatically lock after a determined time of inactivity, you should 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.
Your security administrator might ask you to break the connection to a dialup line when you log out. Breaking the connection to a dialup line:
When computer systems are linked together, they form a network. Operating systems in an OpenVMS network are able to communicate with each other and share information and resources. Each system in a network is called a network node or host and is identified by a unique name or address. Host and node are used interchangeably, and mean a system connected to a network.
With OpenVMS, you have a choice of networking protocols. You can use
the Compaq TCP/IP Services for OpenVMS product or Compaq's DECnet
products within a single network, or you can have an environment where
both products exist. Compaq's primary network strategy for OpenVMS is
TCP/IP, the industry-standard network protocol suite.
1.14.1 Network Nodes
When you are logged in to a network node, you can communicate with other nodes in the network. The node at which you are logged in is called the local node; other nodes on the network are called remote nodes. If you have access to an account on a remote node, you can log in to that account from your local node and perform tasks on that node while remaining connected to your local node.
Section 1.5.2 describes how to log in to a remote node. Additional tasks
you can perform on remote nodes are described in the appropriate
chapters of this manual.
1.14.2 Executing Programs over Networks
Because of support provided by TCP/IP and DECnet software, programs can execute across the network as if they were executing locally. Because the network software is integrated within the operating system, it is easy to write programs that access remote files. To access a remote file in an application program, you need only include the name of the remote node and any required access control information in the file specification.
Task-to-task communications, a feature common to all TCP/IP or DECnet implementations, allows two application programs running on the same or different operating systems to communicate with each other regardless of the programming languages used. Examples of network applications are distributed processing applications, transaction processing applications, and applications providing connection to servers.
In the examples of remote operations in this manual, proxy accounts enable users to perform operations on remote systems. Proxy accounts are one way users can access remote systems. For additional ways to access remote systems, see the OpenVMS System Manager's Manual.
The DIGITAL Command Language (DCL) is a set of English-like instructions that tell the operating system to perform specific operations. DCL provides you with over 200 commands and functions to use in communicating with the operating system to accomplish computing tasks. DCL commands let you do the following:
The following table lists the DCL commands you use to perform a few common computing tasks:
|COPY||Makes a copy of a specified file|
|COPY/FTP||Transfers files between hosts over a TCP/IP network|
|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 this chapter you will learn how to use the DIGITAL Command Language. This chapter includes information about:
Differences in Your Local Environment
Note that this manual covers standard DCL commands only. System managers at your site may customize your system to support the local environment. They might decide to:
For additional information on the commands, qualifiers, and parameters
discussed in this chapter, refer to the OpenVMS DCL Dictionary and online help.
2.1 Entering Commands
To enter a DCL command, type the command at the DCL prompt ($) and press Enter. DCL is not usually case sensitive; you can enter commands in either uppercase or lowercase letters.1
In the following example, the DCL command SHOW TIME is entered as follows:
$ SHOW TIME
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-2002 15:41:43 $
You can use DCL in the following two modes:
When you enter a DCL command, it is read and translated by the DCL interpreter. The way the command interpreter responds to a command is determined by the type of command entered. The three types of DCL commands are as follows:
1 For information on case sensitivity, see Chapter 5.
2.2 The DCL Command Line
DCL, like any language, has its own vocabulary and usage rules. 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:
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:
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 Enter 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.
2.2.3 Using Defaults
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. For parameter defaults, see the sections in this manual that describe the specific DCL command. Qualifier defaults are described in Section 2.5.
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:
End the command line with a hyphen (-) and press Enter.
The system displays an underscore (_) followed by the DCL prompt ($).
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.
Note the following:
The following example shows how to enter a multiple line command:
$ COPY/LOG FORMAT.TXT,FIGURE.TXT,ARTWORK.TXT - _$ SAVE.TXT
You can use the DCL command PIPE to create complex command processing statements from a single DCL command. For example, you can execute one or more of the following operations from the same DCL command line:
For more detailed information, see Section 14.20 and the description of
the PIPE command in the OpenVMS DCL Dictionary: N--Z.
2.3 Rules for Entering DCL Commands
The following rules apply when entering DCL commands. Refer to Chapter 5 for information about using extended file names in DCL commands.
$ PRIN/COPI=2 FORMAL_ART.TXT $ PRINT/COPIES=2 FORMAL_ART.TXT
1 You use symbols, described in Chapter 12, to pass information to the system in an abbreviated manner.
2 A lexical function, described in Chapter 15, obtains information from the system.
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