scanf, fscanf, sscanf, vscanf, vsscanf, vfscanf - input format conversion
#include <stdio.h>
int
scanf(const char *format, ...);
int
fscanf(FILE *stream, const char *format, ...);
int
sscanf(const char *str, const char *format, ...);
#include <stdarg.h>
int
vscanf(const char *format, va_list ap);
int
vsscanf(const char *str, const char *format, va_list ap);
int
vfscanf(FILE *stream, const char *format, va_list ap);
The scanf() family of functions read input according to the
given format
as described below. This format may contain ``conversion
specifiers'';
the results of such conversions, if any, are stored through
a set of
pointer arguments.
The scanf() function reads input from the standard input
stream stdin,
fscanf() reads input from the supplied stream pointer
stream, and
sscanf() reads its input from the character string pointed
to by str.
The vfscanf() function is analogous to vfprintf(3) and reads
input from
the stream pointer stream using a variable argument list of
pointers (see
stdarg(3)). The vscanf() function scans a variable argument
list from
the standard input and the vsscanf() function scans it from
a string;
these are analogous to the vprintf() and vsprintf() functions, respectively.
Each successive pointer argument must correspond properly
with each successive
conversion specifier (but see ``suppression'' below). All conversions
are introduced by the % (percent sign) character.
The format
string may also contain other characters. Whitespace (such
as blanks,
tabs, or newlines) in the format string match any amount of
whitespace,
including none, in the input. Everything else matches only
itself.
Scanning stops when an input character does not match such a
format character.
Scanning also stops when an input conversion cannot
be made (see
below).
Following the % character introducing a conversion there may
be a number
of flag characters, as follows:
* Suppresses assignment. The conversion that follows
occurs as
usual, but no pointer is used; the result of the
conversion is
simply discarded.
h Indicates that the conversion will be one of dioux
or n and the
next pointer is a pointer to a short int (rather
than int).
l Indicates either that the conversion will be one of
dioux or n
and the next pointer is a pointer to a long int
(rather than
int), or that the conversion will be one of efg and
the next
pointer is a pointer to double (rather than float).
q Indicates that the conversion will be one of dioux
or n and the
next pointer is a pointer to a quad_t (rather than
int).
L Indicates that the conversion will be efg and the
next pointer is
a pointer to long double.
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 characters are scanned
in processing
the conversion. Before conversion begins, most conversions
skip whitespace;
this whitespace 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.
D Equivalent to ld; this exists only for backwards compatibility.
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.
O Equivalent to lo; this exists for backwards compatibility.
u Matches an optionally signed decimal integer; the next
pointer must
be a pointer to unsigned int.
x Matches an optionally signed hexadecimal integer; the
next pointer
must be a pointer to unsigned int.
X Equivalent to x.
f Matches an optionally signed floating-point number;
the next pointer
must be a pointer to float.
e Equivalent to f.
g Equivalent to f.
E Equivalent to f.
G Equivalent to f.
s Matches a sequence of non-whitespace characters; the
next pointer
must be a pointer to char, and the provided array must
be large
enough to accept and store all the sequence and the
terminating NUL
character. The input string stops at whitespace or at
the maximum
field width, whichever occurs first. If specified,
the maximum
field length refers to the sequence being scanned
rather than the
storage space, hence the provided array must be 1
larger for the
terminating NUL character.
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 whitespace is suppressed. To skip
whitespace
first, use an explicit space in the format.
[ 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
whitespace 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 [ character and a
close bracket
] 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.
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.
For backwards compatibility, other conversion characters
(except ` ')
are taken as if they were `%d' or, if uppercase, `%ld', and
a `conversion'
of `% ' causes an immediate return of EOF.
These functions return the number of input items assigned,
which can be
fewer than provided for, or even zero, in the event of a
matching failure.
Zero indicates that, while there was input available,
no conversions
were assigned; typically this is due to an invalid input character,
such as an alphabetic character for a `%d' conversion. The
value EOF is
returned if an input failure occurs before any conversion
such as an endof-file
occurs. If an error or end-of-file occurs after
conversion has
begun, the number of conversions which were successfully
completed is returned.
getc(3), printf(3), strtod(3), strtol(3), strtoul(3)
The functions fscanf(), scanf(), and sscanf() conform to ANSI X3.159-1989
(``ANSI C'').
The functions vscanf(), vsscanf(), and vfscanf() first appeared in
4.3BSD-Reno.
All of the backwards compatibility formats will be removed
in the future.
Numerical strings are truncated to 512 characters; for example, %f and %d
are implicitly %512f and %512d.
OpenBSD 3.6 January 31, 1995
[ Back ] |
