SCANF(3S) COMMAND REFERENCE 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 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 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 nonspace 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. These conversion characters are
Printed 3/13/89 1
SCANF(3S) COMMAND REFERENCE SCANF(3S)
legal:
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 nonspace 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.
d A decimal integer is expected; the corresponding argument
should be an integer pointer.
e A floating point number is expected; the next field is
f 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.
o An octal integer is expected; the corresponding argument
should be a 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.
x Hexadecimal integer is expected; corresponding argument
should be an integer pointer.
% A single % is expected in the input at this point; no
assignment is done.
[ 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 a caret (^), 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
preceeded by l to indicate that a pointer to long rather
than to int is in the argument list. Similarly, the
Printed 3/13/89 2
SCANF(3S) COMMAND REFERENCE SCANF(3S)
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 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.
EXAMPLES
The following call 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':
int i; float x; char name[50];
scanf("%d %f %s", &i, &x, name);
In the next example, the input
56789 0123 56a72
will assign 56 to i, 789.0 to x, skip 0123, and place the
string 56\0 in name.
int i; float x; char name[50];
scanf("%2d %f %*d %[1234567890]", &i, &x, name);
After this, the next call to getchar will return a.
DIAGNOSTICS
Scanf functions return EOF on end of input and a short count
for missing or illegal data items.
CAVEATS
The success of literal matches and suppressed assignments is
not directly determinable.
SEE ALSO
atof(3c), getc(3s), and printf(3s).
Printed 3/13/89 3
%%index%%
na:288,102;
sy:390,1867;
de:2257,2002;4619,2752;7731,992;
ex:8723,881;
di:9604,309;
ca:9913,177;
se:10090,166;
%%index%%000000000144