SCANF(3S) GENIX Programmer's Manual SCANF(3S)
NAME
scanf, fscanf, sscanf - formatted input conversion
SYNOPSIS
#include <stdio.h>
scanf(format [ , pointer ] . . . )
char *format;
fscanf(stream, format [ , pointer ] . . . )
FILE *stream;
char *format;
sscanf(s, format [ , pointer ] . . . )
char *s, *format;
DESCRIPTION
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 for-
mat, and stores the results in its arguments. Each expects as argu-
ments 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 charac-
ter of the input stream.
3. Conversion specifications, consisting of the character %, an
optional assignment suppressing character *, an optional numeri-
cal 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 charac-
ters; 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 res-
tricted type. The following conversion characters are legal:
% a single `%' is expected in the input at this point; no assign-
ment is done.
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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 integer pointer.
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 charac-
ter 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 argu-
ment 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
f 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 remain-
ing 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 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 pre-
ceeded 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
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was done; if conversion was intended, it was frustrated by an inap-
propriate character in the input.
For example, the call
int i; float x; char name[50];
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 con-
tain `thompson\0'. Or,
int i; float x; char name[50];
scanf("%2d%f%*d%[1234567890]", &i, &x, name);
with input
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'.
SEE ALSO
atof(3), getc(3), printf(3)
DIAGNOSTICS
The scanf functions return EOF on end of input, and a short count
for missing or illegal data items.
BUGS
The success of literal matches and suppressed assignments is not
directly determinable.
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