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Online Help in the CLI


Getting Online Help from the Junos OS Command-Line Interface

The Junos OS command-line interface (CLI) has a context-sensitive online help feature that enables you to access information about commands and statements from the Junos OS CLI.

Getting Help About Commands

Information about commands is provided at each level of the CLI command hierarchy. You can type a question mark (?) to get context-relevant help about commands.

  • If you type the question mark at the command-line prompt, the CLI lists the available commands and options. For example, to view a list of top-level operational mode commands, this is the result:

    user@host> ?
  • If you type the question mark after entering the complete name of a command or command option, the CLI lists the available commands and options and then re-displays the command names and options you typed.

    user@host> clear ?
  • If you type the question mark in the middle of a command name, the CLI lists possible command completions that match the letters you have entered so far. It then re-displays the letters that you typed. For example, to list all operational mode commands that start with the letter c, type the following:

    user@host> c?
  • For introductory information on using the question mark or the help command, you can also type help and press Enter:

    user@host> help

Getting Help About a String in a Statement or Command

You can use the help command to display help about a text string contained in a statement or command name:

string is a text string about which you want to get help. This string is used to match statement or command names as well as to match the help strings that are displayed for the statements or commands.

If the string contains spaces, enclose it in quotation marks (" " ). You can also specify a regular expression for the string, using standard UNIX-style regular expression syntax.

For statements or commands which need input data type as STRING, the supported characters set is as follows:

  • Any printable ASCII characters

  • For characters with space, it should be enclosed in double-quotes

  • To have double-quote as the input, it should be escaped with ‘\’


    No escape characters are supported in a string other than to escape from double quotes.

  • The range of supported characters for attributes is 0 through 65499 characters.

  • The range of supported characters for string type identifiers is 1 through 255 characters.

In configuration mode, this command displays statement names and help text that match the string specified. In operational mode, this command displays command names and help text that match the string specified.

Getting Help About Configuration Statements

You can display help based on text contained in a statement name using the help topic and help reference commands:

The help topic command displays usage guidelines for the statement based on information that appears in the Junos OS configuration guides. The help reference command displays summary information about the statement based on the summary descriptions that appear in the Junos OS configuration guides.

Getting Help About System Log Messages

You can display help based on a system log tag using the help syslog command:

The help syslog command displays the contents of a system log message.

Junos OS CLI Online Help Features

Help for Omitted Statements

If you have omitted a required statement at a specific hierarchy level, when you attempt to move from that hierarchy level or when you issue the show command in configuration mode, a message indicates which statement is missing. For example:


Using CLI Command Completion

The Junos OS CLI provides you a command completion option that enables Junos OS to recognize commands and options based on the initial few letters you typed. That is, you do not always have to remember or type the full command or option name for the CLI to recognize it.

  • To display all possible command or option completions, type the partial command followed immediately by a question mark.

  • To complete a command or option that you have partially typed, press Tab or Space. If the partially typed letters begin a string that uniquely identifies a command, the complete command name appears. Otherwise, a prompt indicates that you have entered an ambiguous command, and the possible completions are displayed.

Command completion also applies to other strings, such as filenames, interface names, and usernames. To display all possible values, type a partial string followed immediately by a question mark. To complete a string, press Tab.

Using Command Completion in Configuration Mode

The CLI command completion functions also apply to the commands in configuration mode and to configuration statements. Specifically, to display all possible commands or statements, type the partial string followed immediately by a question mark. To complete a command or statement that you have partially typed, press Tab or Space.

Displaying Tips About CLI Commands

To get tips about CLI commands, issue the help tip cli command. Each time you enter the command, a new tip appears. For example:

You can also enter help tip cli number to associate a tip with a number. This enables you to recall the tip later. For example:

CLI Explorer Overview

CLI Explorer is a Web application that helps you to explore Junos OS configuration statements and commands. It lists all the configuration statements and commands supported in the Junos OS across different platforms on several products.

To view the available configuration statements and commands, you can use any of the following filtering options:

  • Filter by product family—To find the CLI reference information by product family, you can either select “All products” or select any specific product.

    For example: ACX Series, EX Series.

  • Filter by number or letter—To find the CLI reference information by number or letter, you can either select “All” or filter by numbers “3” or “8” or any of the letters (“A”, “B”, “C”...).

    For example, if you select the letter “A”, commands such as aaa, aaa clients (TDF), aaa-access-profile (L2TP LNS) appear.

  • Filter by the normal search option—To use this option to filter the commands and statements, you enter your search criteria.

    For example, if you enter the number “3”, all the commands and statements containing the number “3” appear in the search results.

When you click on the link in the search results, you are directed to a page describing the command or statement that is referenced in a user guide.

To explore the Junos OS configuration statements and commands, see the CLI Explorer.