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The family of functions scans input according to a as
described below. This format may contain the results from such conversions,
if any, are stored through the arguments. The function reads input from
the standard input stream reads input from the stream pointer and reads
its input from the character string pointed to by The function is analogous
to and reads input from the stream pointer using a variable argument
list of pointers (see The function scans a variable argument list from
the standard input and the function scans it from a string; these are
analogous to the and functions respectively. Each successive argument
must correspond properly with each successive conversion specifier (but
see ‘suppression’ below). All conversions are introduced by the (percent
sign) character. The string may also contain other characters. White space
(such as blanks, tabs, or newlines) in the string match any amount of
white space, including none, in the input. Everything else matches only
itself. Scanning stops when an input character does not match such a format
character. Scanning also stops when an input conversion cannot be made (see
below).
Following the character introducing a conversion there
may be a number of characters, as follows: Suppresses assignment. The
conversion that follows occurs as usual, but no pointer is used; the result
of the conversion is simply discarded. Indicates that the conversion will
be one of or and the next pointer is a pointer to a (rather than Indicates
either that the conversion will be one of or and the next pointer is
a pointer to a (rather than or that the conversion will be one of and
the next pointer is a pointer to (rather than Indicates that the conversion
will be one of or and the next pointer is a pointer to a (rather than
Indicates that the conversion will be and the next pointer is a pointer
to In addition to these flags, there may be an optional maximum field
width, expressed as a decimal integer, between the and the conversion.
If no width is given, a default of ‘infinity’ is used (with one exception,
below); otherwise at most this many characters are scanned in processing
the conversion. Before conversion begins, most conversions skip white space;
this white space is not counted against the field width. The following
conversions are available: Matches a literal ‘%’. That is, ‘%%’ in the format
string matches a single input ‘%’ character. No conversion is done, and assignment
does not occur. Matches an optionally signed decimal integer; the next
pointer must be a pointer to Equivalent to this exists only for backwards
compatibility. Matches an optionally signed integer; the next pointer must
be a pointer to The integer is read in base 16 if it begins with or
in base 8 if it begins with and in base 10 otherwise. Only characters that
correspond to the base are used. Matches an octal integer; the next pointer
must be a pointer to Equivalent to this exists for backwards compatibility.
Matches an optionally signed decimal integer; the next pointer must be
a pointer to Matches an optionally signed hexadecimal integer; the next
pointer must be a pointer to Equivalent to Matches an optionally signed
floating-point number; the next pointer must be a pointer to Equivalent
to Equivalent to Equivalent to Equivalent to Matches a sequence
of non-white-space characters; the next pointer must be a pointer to and
the array must be large enough to accept all the sequence and the terminating
character. The input string stops at white space or at the maximum field
width, whichever occurs first. Matches a sequence of count characters
(default 1); the next pointer must be a pointer to and there must be enough
room for all the characters (no terminating is added). The usual skip of
leading white space is suppressed. To skip white space first, use an explicit
space in the format. Matches a nonempty sequence of characters from the
specified set of accepted characters; the next pointer must be a pointer
to and there must be enough room for all the characters in the string,
plus a terminating character. The usual skip of leading white space is
suppressed. The string is to be made up of characters in (or not in) a particular
set; the set is defined by the characters between the open bracket character
and a close bracket character. The set those characters if the first character
after the open bracket is a circumflex To include a close bracket in the
set, make it the first character after the open bracket or the circumflex;
any other position will end the set. The hyphen character is also special;
when placed between two other characters, it adds all intervening characters
to the set. To include a hyphen, make it the last character before the final
close bracket. For instance, means the set ‘everything except close bracket,
zero through nine, and hyphen’. The string ends with the appearance of a
character not in the (or, with a circumflex, in) set or when the field
width runs out. Matches a pointer value (as printed by in the next pointer
must be a pointer to Nothing is expected; instead, the number of characters
consumed thus far from the input is stored through the next pointer, which
must be a pointer to This is a conversion, although it can be suppressed
with the flag. For backwards compatibility, other conversion characters
(except are taken as if they were or, if uppercase, and a ‘conversion’
of causes an immediate return of
These functions return
the number of input items assigned, which can be fewer than provided for,
or even zero, in the event of a matching failure. Zero indicates that, while
there was input available, no conversions were assigned; typically this
is due to an invalid input character, such as an alphabetic character for
a conversion. The value is returned if an input failure occurs before
any conversion such as an end-of-file occurs. If an error or end-of-file occurs
after conversion has begun, the number of conversions which were successfully
completed is returned.
The functions and conform
to
The functions and are new to this release.
All of the
backwards compatibility formats will be removed in the future. Numerical
strings are truncated to 512 characters; for example, and are implicitly
and
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