Understanding Command Line Syntax

When working with command line interfaces (CLI), it’s essential to understand the syntax and formatting used to create and execute commands. The command line syntax can include special characters and conventions that dictate how commands should be structured and what elements are required or optional. Let’s break down the common command line syntax elements using examples from both a general explanation and a specific CLI usage sample.

Command Line Syntax Elements

Square Brackets [ ]

The square brackets ( [ ] ) in command line syntax indicate that the enclosed element, which can be a parameter, value, or information, is optional. Users have the choice to include one or more items within the square brackets or omit them entirely. It’s important not to type the square brackets themselves in the actual command line.

Example:

• [global options]: This means you can include global options if needed.
• [source arguments]: These are optional source-related arguments.
• [destination arguments]: These are optional destination-related arguments.

Angle Brackets < >

Angle brackets ( < > ) signify that the enclosed element is mandatory. Users are required to replace the text within the angle brackets with the appropriate information, without typing the angle brackets themselves in the command line.

Example:

• -f [set the File Name variable]: You must provide a value for the File Name variable.
• -printer <*printer name*>: Replace <printer name> with the actual printer name.
• -repeat <months> <days> <hours> <minutes>: You need to specify values for months, days, hours, and minutes.
• date access <mm/dd/yyyy>: Replace <mm/dd/yyyy> with a valid date.

Ellipsis …

The ellipsis symbol ( ... ) implies “and so on” and indicates that the preceding element can be repeated multiple times in a command line. This is often used when you can specify multiple items of the same type.

Example:

• -jobid <job id1, job id2, job id3,...>: You can include one or more job IDs.
• [-exitcode <exit code 1>,<exit code2>,<exit code3> ...]: You can provide one or more exit codes.

Pipe |

The pipe symbol ( | ) denotes “or” and represents a choice within an element. If two arguments are separated by the pipe symbol, users can select either the element to the left or the one to the right of the separator. It’s not possible to choose both elements in a single command. Within square brackets, the choices are optional, while within angle brackets, at least one choice is required.

Example:

• -ca_backup [-custom|-rotation|-gfsrotation]: You can choose one of the options, such as -custom, -rotation, or -gfsrotation.
• -excludeday <Sun|Mon|Tue|Wed|Thu|Fri|Sat>: You must select one of the days of the week.

Italics

Italic text indicates that you need to supply a value for the associated parameter or option. It serves as a placeholder for user-specific input.

Example:

• -sessionpassword *session password*: Replace *session password* with the actual session password.
• -f [set the File Name variable]: Provide a value for the File Name variable.
• -printer <*printer name*>: Replace <printer name> with the desired printer name.

CLI Usage Sample

Let’s explore a specific CLI usage sample to apply the concepts discussed above:

Naval Fate CLI

Usage:

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naval_fate ship new <name>...
naval_fate ship <name> move <x> <y> [--speed=<kn>]
naval_fate ship shoot <x> <y>
naval_fate mine (set|remove) <x> <y> [--moored|--drifting]
naval_fate -h | --help
naval_fate --version

Options:

• -h --help: Display the help screen.
• --version: Show the version.
• --speed=<kn>: Specify the speed in knots (default is 10).
• --moored: Set a moored (anchored) mine.
• --drifting: Set a drifting mine.

In this example:

• <name> in the naval_fate ship new <name>... command is mandatory, and you can provide one or more names.
• <name>, <x>, and <y> in various ship-related commands are mandatory placeholders.
• [--speed=<kn>] in the ship move command is optional, allowing you to specify the speed.
• (set|remove) in the mine command presents a choice between ‘set’ and ‘remove’.
• [--moored|--drifting] in the mine command offers a choice between ‘moored’ and ‘drifting’.
• -h or --help and --version are standalone options that can be used without additional arguments.

Understanding these syntax elements is crucial for effectively using and constructing commands in a CLI.