scanf, fscanf, sscanf, vscanf, vfscanf, vsscanf - formatted input
int scanf(const char *format [, pointer] ...)
int fscanf(FILE *stream, const char *format [, pointer] ...)
int sscanf(const char *s, const char *format [, pointer] ...)
int vscanf(const char *format, va_list args)
int vfscanf(FILE *stream, const char *format, va_list args)
int vsscanf(const char *s, const char *format, va_list args)
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, interprets 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 v*scanf functions can be used to make functions like the first three
by using the stdarg(3) method to process the argument pointers.
The control string usually contains conversion specifications, which are
used to direct interpretation of input sequences. The control string may
1. Blanks, tabs or newlines, which match optional white space in the
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 suppressing character *, an optional numerical maximum
field width, and a conversion character.
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 suppression was indicated by *.
An input field is defined as a string of non-space characters; it extends
to the next inappropriate character or until the field width, if
specified, is exhausted.
The conversion character indicates the interpretation of the input field;
the corresponding pointer argument must usually be of a restricted type.
The following conversion characters are legal:
% a single `%' is expected in the input at this point; no assignment is
d a decimal integer is expected; the corresponding argument should be
an integer pointer.
o an octal integer is expected; the corresponding argument should be a
x a hexadecimal integer is expected; the corresponding argument should
be an integer pointer.
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 character 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
efg a floating point number is expected; the next field is converted
accordingly and 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 possibly 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 followed 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 circumflex (^), 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 character array.
The conversion characters d, o and x may be capitalized or preceded by l
to indicate that a pointer to long rather than to int is in the argument
list. Similarly, the conversion characters e, f or g 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 preceded by h to indicate 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 input.
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), stdarg(3).
The scanf functions return EOF on end of input, and a short count for
missing or illegal data items.
The success of literal matches and suppressed assignments is not directly