#include <stdio.h>
int scanf(format [ , pointer... ] ) char *format;
int fscanf(stream, format [ , pointer... ] ) FILE *stream; char *format;
int sscanf(s, format [ , pointer... ] ) char *s, *format;
The following are provided for XPG2 compatibility:
#define nl_scanf scanf #define nl_fscanf fscanf #define nl_sscanf sscanf
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 results are undefined in there are insufficient args for the format. If the format is exhausted while args remain, the excess args are simply ignored.
The control string usually contains conversion specifications, which are used to direct interpretation of input sequences. The control string may contain:
Conversion specifications are introduced by the character % or the character sequence %digit$. 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 `*'. The suppression of assignment provides a way of describing an input field which is to be skipped. 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. For all descriptors except ``['' and ``c'', white space leading an input field is ignored.
The conversion character indicates the interpretation of the input field; the corresponding pointer argument must usually be of a restricted type. For a suppressed field, no pointer argument is given. The following conversion characters are legal:
The conversion characters d, u, o, x, and i may be preceded by l or h to indicate that a pointer to long or to short rather than to int is in the argument list. Similarly, the conversion characters e, f, and g may be preceded by l to indicate that a pointer to double rather than to float is in the argument list. The l or h modifier is ignored for other conversion characters.
Avoid this common error: because printf.3v does not require that the lengths of conversion descriptors and actual parameters match, coders sometimes are careless with the scanf() functions. But converting %f to &double or %lf to &float does not work; the results are quite incorrect.
scanf() conversion terminates at EOF, at the end of the control string, or when an input character conflicts with the control string. In the latter case, the offending character is left unread in the input stream.
scanf() returns the number of successfully matched and assigned input items; this number can be zero in the event of an early conflict between an input character and the control string. The constant EOF is returned upon end of input. Note: 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.
If the input ends before the first conflict or conversion,
EOF
is returned. If the input ends after the first conflict or conversion,
the number of successfully matched items is returned.
Conversions can be applied to the nth argument in the argument list, rather than the next unused argument. In this case, the conversion character % (see below) is replaced by the sequence %digit$, where digit is a decimal integer n in the range [1,9], giving the position of the argument in the argument list. This feature provides for the definition of format strings that select arguments in an order appropriate to specific languages.
The format string can contain either form of a conversion specification, that is % or %digit$, although the two forms cannot be mixed within a single format string.
All forms of the scanf() functions allow for the detection of a language dependent radix character in the input string. The radix character is defined by the program's locale (category LC_NUMERIC). In the "C" locale, or in a locale where the radix character is not defined, the radix character defaults to `.'.
FORMFEED is allowed as a white space character in control strings.
XPG2 requires that nl_scanf, nl_fscanf and nl_sscanf be defined as scanf, fscanf and sscanf, respectively for backward compatibility.
If any items are converted, scanf(), fscanf() and sscanf() return the number of items converted successfully. This number may smaller than the number of items requested. If no items are converted, these functions return 0. scanf(), fscanf() and sscanf() return EOF on end of input.
int i, n; float x; char name[50]; n = scanf("%d%f%s", &i, &x, name);
with the input line:
will assign to n the value 3, to i the value 25, to x the value 5.432, and name will contain thompson\0. Or:
int i, j; float x; char name[50]; (void) scanf("%i%2d%f%*d %[0-9]", &j, &i, &x, name);
with input:
will assign 9 to j, 56 to i, 789.0 to x, skip 0123, and place the string 56\0 in name. The next call to getchar() (see getc.3v will return a. Or:
int i, j, s, e; char name[50]; (void) scanf("%i %i %n%s%n", &i, &j, &s, name, &e);
with input:
will assign 17 to i, 0 to j, 6 to s, will place the string xy\0 in name, and will assign 8 to e. Thus, the length of name is e - s = 2. The next call to getchar() (see getc.3v will return a SPACE.
getc.3v
printf.3v
setlocale.3v
stdio.3v
string_to_decimal.3
strtol.3
Trailing white space (including a NEWLINE) is left unread unless matched in the control string.
The success of literal matches and suppressed assignments is not directly determinable.
Created by unroff & hp-tools. © somebody (See intro for details). All Rights Reserved. Last modified 11/5/97