Template:cpp/utility/format/format string

an object that represents the format string. The format string consists of
 * ordinary characters (except {{c| { }} and {{c| } }}), which are copied unchanged to the output,
 * escape sequences and, which are replaced with {{c| { }} and {{c| } }} respectively in the output, and
 * replacement fields.

Each replacement field has the following format:

@1@ replacement field without a format specification @2@ replacement field with a format specification


 * For basic types and standard string types, the format specification is interpreted as standard format specification.
 * For chrono types, the format specification is interpreted as chrono format specification.
 * For std, the format specification is interpreted as thread id format specification.
 * For other formattable types, the format specification is determined by user-defined specializations.