プログラマ専用SNS ミクプラ

[ Matches a nonempty sequence of characters from a set of expected characters
(the scanset). 286)
If no l length modifier is present, the corresponding argument shall be a
pointer to the initial element of a character array large enough to accept the
sequence and a terminating null character, which will be added automatically.

(中略)

The conversion specifier includes all subsequent characters in the format
string, up to and including the matching right bracket (]). The characters
between the brackets (the scanlist) compose the scanset, unless the character
after the left bracket is a circumflex (^), in which case the scanset contains all
characters that do not appear in the scanlist between the circumflex and the
right bracket. If the conversion specifier begins with [] or [^], the right
bracket character is in the scanlist and the next following right bracket
character is the matching right bracket that ends the specification; otherwise
the first following right bracket character is the one that ends the
specification. If a - character is in the scanlist and is not the first, nor the
second where the first character is a ^, nor the last character, the behavior is
implementation-defined.