How to read syntax diagrams
The syntactical structure of commands described in this document is shown by means of syntax diagrams.
- An item is a keyword or a variable.
- An item is required or optional.
- A choice is available.
- A default applies if you do not specify a value.
- You can repeat an item.
Syntax
COMMAND_NAMErequired_variable [ OPTIONAL_KEYWORD=variable ] [ { KEYWORD=default_choice | KEYWORD= { choice2 | choice3 } } ] repeatable_item1 [ <fragment_name> ] [ { optional_choice1 | optional_choice2 } ] { required_choice1 | required_choice2 | required_choice3 } repeatable_item2 [ { DEFAULT_KEYWORD | KEYword } ]Here are some tips for reading and understanding syntax diagrams:
- Order of
reading - Read the syntax diagrams from left to right, from top to bottom,
following the path of the line.
The ►►─── symbol indicates the beginning of a statement.
The ───► symbol indicates that a statement is continued on the next line.
The ►─── symbol indicates that a statement is continued from the previous line.
The ───►◄ symbol indicates the end of a statement.
- Keywords
- Keywords appear in uppercase letters.
COMMAND_NAME
Sometimes you only need to type the first few letters of a keyword, The required part of the keyword appears in uppercase letters.
[ { DEFAULT_KEYWORD | KEYword } ]In this example, you could type "KEY", "KEYW", "KEYWO", "KEYWOR" or "KEYWORD".
The abbreviated or whole keyword you enter must be spelled exactly as shown.
- Variables
- Variables appear in lowercase letters. They represent user-supplied names
or values.
required_variable
- Required
items - Required items appear on the horizontal line (the main path).
COMMAND_NAMErequired_variable
- Optional
items - Optional items appear below the main path.
[ OPTIONAL_KEYWORD=variable ]
- Choice of
items - If you can choose from two or more items, they appear
vertically, in a stack.
If you must choose one of the items, one item of the stack appears on the main path.
{ required_choice1 | required_choice2 | required_choice3 }If choosing one of the items is optional, the entire stack appears below the main path.
[ { optional_choice1 | optional_choice2 } ]If a default value applies when you do not choose any of the items, the default value appears above the main path.
[ { DEFAULT_KEYWORD | KEYWORD1 | KEYWORD2 } ] - Repeatable
items - An arrow returning to the left above the main
line indicates an item that can be repeated.
repeatable_item1
If you need to specify a separator character (such as a comma) between repeatable items, the line with the arrow returning to the left shows the separator character you must specify.
repeatable_item2 - Fragments
- Where it makes the syntax diagram easier to read, a section
or fragment of the syntax is sometimes shown separately.
[ <fragment_name> ]