scanf, fscanf, sscanf - formatted input conversion
scanf(format [ , pointer ] . . . )
fscanf(stream, format [ , pointer ] . . . )
sscanf(s, format [ , pointer ] . . . )
char *s, *format;
Scanf reads from the standard input stream stdin. Fscanf reads from the named input
stream. Sscanf reads from the character string s. Each function reads characters, inter-
prets them according to a format, and stores the results in its arguments. Each expects
as arguments a control string format, described below, and a set of pointer arguments
indicating where the converted input should be stored.
The control string usually contains conversion specifications, which are used to direct
interpretation of input sequences. The control string may contain:
1. Blanks, tabs or newlines, which match optional white space in the input.
2. An ordinary character (not %) which must match the next character of the input stream.
3. Conversion specifications, consisting of the character %, an optional assignment sup-
pressing character *, an optional numerical maximum field width, and a conversion
A conversion specification directs the conversion of the next input field; the result is
placed in the variable pointed to by the corresponding argument, unless assignment sup-
pression was indicated by *. An input field is defined as a string of non-space charac-
ters; it extends to the next inappropriate character or until the field width, if speci-
fied, is exhausted.
The conversion character indicates the interpretation of the input field; the correspond-
ing pointer argument must usually be of a restricted type. The following conversion char-
acters are legal:
% a single `%' is expected in the input at this point; no assignment is done.
d a decimal integer is expected; the corresponding argument should be an integer
o an octal integer is expected; the corresponding argument should be a integer pointer.
x a hexadecimal integer is expected; the corresponding argument should be an integer
s a character string is expected; the corresponding argument should be a character
pointer pointing to an array of characters large enough to accept the string and a
terminating `\0', which will be added. The input field is terminated by a space char-
acter or a newline.
c a character is expected; the corresponding argument should be a character pointer.
The normal skip over space characters is suppressed in this case; to read the next
non-space character, try `%1s'. If a field width is given, the corresponding argument
should refer to a character array, and the indicated number of characters is read.
e a floating point number is expected; the next field is converted accordingly and
f stored through the corresponding argument, which should be a pointer to a float. The
input format for floating point numbers is an optionally signed string of digits pos-
sibly containing a decimal point, followed by an optional exponent field consisting of
an E or e followed by an optionally signed integer.
[ indicates a string not to be delimited by space characters. The left bracket is fol-
lowed by a set of characters and a right bracket; the characters between the brackets
define a set of characters making up the string. If the first character is not cir-
cumflex (^), the input field is all characters until the first character not in the
set between the brackets; if the first character after the left bracket is ^, the
input field is all characters until the first character which is in the remaining set
of characters between the brackets. The corresponding argument must point to a char-
The conversion characters d, o and x may be capitalized or preceeded by l to indicate that
a pointer to long rather than to int is in the argument list. Similarly, the conversion
characters e or f may be capitalized or preceded by l to indicate a pointer to double
rather than to float. The conversion characters d, o and x may be preceeded by h to indi-
cate a pointer to short rather than to int.
The scanf functions return the number of successfully matched and assigned input items.
This can be used to decide how many input items were found. The constant EOF is returned
upon end of input; note that this is different from 0, which means that no conversion was
done; if conversion was intended, it was frustrated by an inappropriate character in the
For example, the call
int i; float x; char name;
scanf( "%d%f%s", &i, &x, name);
with the input line
25 54.32E-1 thompson
will assign to i the value 25, x the value 5.432, and name will contain `thompson\0'. Or,
int i; float x; char name;
scanf("%2d%f%*d%", &i, &x, name);
56789 0123 56a72
will assign 56 to i, 789.0 to x, skip `0123', and place the string `56\0' in name. The
next call to getchar will return `a'.
atof(3), getc(3), printf(3)
The scanf functions return EOF on end of input, and a short count for missing or illegal
The success of literal matches and suppressed assignments is not directly determinable.