Manual Pages  — SCANF

#include <stdio.h>

#include <stdarg.h>

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 bytes are scanned in processing the conversion. In the case of the lc, ls and l[ conversions, the field width specifies the maximum number of multibyte characters that will be scanned. 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.
d	Matches an optionally signed decimal integer; the next pointer must be a pointer to int.
i	Matches an optionally signed integer; the next pointer must be a pointer to int. The integer is read in base 16 if it begins with ‘0x’ or ‘0X’, in base 8 if it begins with ‘0’, and in base 10 otherwise. Only characters that correspond to the base are used.
o	Matches an octal integer; the next pointer must be a pointer to unsigned int.
u	Matches an optionally signed decimal integer; the next pointer must be a pointer to unsigned int.
x, X	Matches an optionally signed hexadecimal integer; the next pointer must be a pointer to unsigned int.
a, A, e, E, f, F, g, G
	Matches a floating-point number in the style of strtod(3). The next pointer must be a pointer to float (unless l or L is specified.)
s	Matches a sequence of non-white-space characters; the next pointer must be a pointer to char, and the array must be large enough to accept all the sequence and the terminating NUL character. The input string stops at white space or at the maximum field width, whichever occurs first. If an l qualifier is present, the next pointer must be a pointer to wchar_t, into which the input will be placed after conversion by mbrtowc(3).
S	The same as ls.
c	Matches a sequence of width count characters (default 1); the next pointer must be a pointer to char, and there must be enough room for all the characters (no terminating NUL is added). The usual skip of leading white space is suppressed. To skip white space first, use an explicit space in the format. If an l qualifier is present, the next pointer must be a pointer to wchar_t, into which the input will be placed after conversion by mbrtowc(3).
C	The same as lc.
amp;[	Matches a nonempty sequence of characters from the specified set of accepted characters; the next pointer must be a pointer to char, and there must be enough room for all the characters in the string, plus a terminating NUL 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 amp;[ character and a close bracket amp;] character. The set excludes 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, ‘[^]0-9-]’ 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. If an l qualifier is present, the next pointer must be a pointer to wchar_t, into which the input will be placed after conversion by mbrtowc(3).
p	Matches a pointer value (as printed by ‘%p’ in printf(3)); the next pointer must be a pointer to void.
n	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 int. This is not a conversion, although it can be suppressed with the * flag.

The decimal point character is defined in the program's locale (category LC_NUMERIC).

For backwards compatibility, a "conversion" of ‘%\0’ causes an immediate return of EOF.

Numerical strings are truncated to 512 characters; for example, %f and %d are implicitly %512f and %512d.

The %n$ modifiers for positional arguments are not implemented.

The scanf family of functions do not correctly handle multibyte characters in the format argument.