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3.1.2 Statements

A simple statement consists of a keyword and value separated by any amount of whitespace. The statement is terminated with a semicolon (‘;’).

Examples of simple statements are:

pidfile /var/run/pies.pid;
source-info yes;
debug 10;

A keyword begins with a letter and may contain letters, decimal digits, underscores (‘_’) and dashes (‘-’). Examples of keywords are: ‘group’, ‘control-file’.

A value can be one of the following:

number

A number is a sequence of decimal digits.

boolean

A boolean value is one of the following: ‘yes’, ‘true’, ‘t’ or ‘1’, meaning true, and ‘no’, ‘false’, ‘nil’, ‘0’ meaning false.

unquoted string

An unquoted string may contain letters, digits, and any of the following characters: ‘_’, ‘-’, ‘.’, ‘/’, ‘:’.

quoted string

A quoted string is any sequence of characters enclosed in double-quotes (‘"’). A backslash appearing within a quoted string introduces an escape sequence, which is replaced with a single character according to the following rules:

SequenceReplaced with
\aAudible bell character (ASCII 7)
\bBackspace character (ASCII 8)
\fForm-feed character (ASCII 12)
\nNewline character (ASCII 10)
\rCarriage return character (ASCII 13)
\tHorizontal tabulation character (ASCII 9)
\vVertical tabulation character (ASCII 11)
\\A single backslash (‘\’)
\"A double-quote.

Table 3.1: Backslash escapes

In addition, any occurrence of ‘\’ immediately followed by a newline character (ASCII 10) is removed from the string. This allows to split long strings over several physical lines, e.g.:

"a long string may be\
 split over several lines"

If the character following a backslash is not one of those specified above, the backslash is ignored and a warning is issued.

Here-document

Here-document is a special construct that allows to introduce strings of text containing embedded newlines.

The <<word construct instructs the parser to read all the following lines up to the line containing only word, with possible trailing blanks. Any lines thus read are concatenated together into a single string. For example:

<<EOT
A multiline
string
EOT

Body of a here-document is interpreted the same way as double-quoted string, unless word is preceded by a backslash (e.g. ‘<<\EOT’) or enclosed in double-quotes, in which case the text is read as is, without interpretation of escape sequences.

If word is prefixed with - (a dash), then all leading tab characters are stripped from input lines and the line containing word. Furthermore, if - is followed by a single space, all leading whitespace is stripped from them. This allows to indent here-documents in a natural fashion. For example:

<<- TEXT
    All leading whitespace will be
    ignored when reading these lines.
TEXT

It is important that the terminating delimiter be the only token on its line. The only exception to this rule is allowed if a here-document appears as the last element of a statement. In this case a semicolon can be placed on the same line with its terminating delimiter, as in:

help-text <<-EOT
        A sample help text.
EOT;
list

A list is a comma-separated list of values. Lists are delimited by parentheses. The following example shows a statement whose value is a list of strings:

dependents (pmult, auth);

In any case where a list is appropriate, a single value is allowed without being a member of a list: it is equivalent to a list with a single member. This means that, e.g. ‘dependents auth;’ is equivalent to ‘dependents (auth);’.

A block statement introduces a logical group of another statements. It consists of a keyword, followed by an optional value, and a sequence of statements enclosed in curly braces, as shown in the example below:

component multiplexor {
        command "pmult";
}

The closing curly brace may be followed by a semicolon, although this is not required.


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