Editing String literal (section)

== String interpolation ==
{{main|String interpolation}}
In some languages, string literals may contain placeholders referring to variables or expressions in the current [[Scope (computer science)|context]], which are evaluated (usually at run time). This is referred to as ''variable interpolation'', or more generally [[string interpolation]]. Languages that support interpolation generally distinguish strings literals that are interpolated from ones that are not. For example, in [[bourne shell|sh-compatible Unix shells]] (as well as Perl and Ruby), double-quoted (quotation-delimited, ") strings are interpolated, while single-quoted (apostrophe-delimited, <nowiki>'</nowiki>) strings are not. Non-interpolated string literals are sometimes referred to as "raw strings", but this is distinct from "raw string" in the sense of escaping. For example, in Python, a string prefixed with <code>r</code> or <code>R</code> has no escaping or interpolation, a normal string (no prefix) has escaping but no interpolation, and a string prefixed with <code>f</code> or <code>F</code> has escaping and interpolation.

For example, the following [[Perl]] code:

<syntaxhighlight lang="perl">
$name     = "Nancy";
$greeting = "Hello World";
print "$name said $greeting to the crowd of people.";
</syntaxhighlight>

produces the output:

 Nancy said Hello World to the crowd of people.

In this case, the [[metacharacter]] character ($) (not to be confused with the [[Sigil (computer programming)|sigil]] in the variable assignment statement) is interpreted to indicate variable interpolation, and requires some escaping if it needs to be outputted literally.

This should be contrasted with the <code>[[printf]]</code> function, which produces the same output using notation such as:

<syntaxhighlight lang="perl">printf "%s said %s to the crowd of people.", $name, $greeting;</syntaxhighlight>

but does not perform interpolation: the <code>%s</code> is a placeholder in a [[printf format string]], but the variables themselves are outside the string.

This is contrasted with "raw" strings:

<syntaxhighlight lang="perl">print '$name said $greeting to the crowd of people.';</syntaxhighlight>

which produce output like:

 $name said $greeting to the crowd of people.

Here the $ characters are not metacharacters, and are not interpreted to have any meaning other than plain text.