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scanf, fscanf, sscanf, scanf_s, fscanf_s, sscanf_s

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< c‏ | io

معرفة في ملف <stdio.h>
(1)
int scanf( const char          *format, ... );
(حتى C99)
int scanf( const char *restrict format, ... );
(منذ C99)
(2)
int fscanf( FILE          *stream, const char          *format, ... );
(حتى C99)
int fscanf( FILE *restrict stream, const char *restrict format, ... );
(منذ C99)
(3)
int sscanf( const char          *buffer, const char          *format, ... );
(حتى C99)
int sscanf( const char *restrict buffer, const char *restrict format, ... );
(منذ C99)


تقرأ من المواضع المحددة وتترجمها حسب الشروط في ‎format‎ ثم تخزنها في الأماكن المعطاه.

1) تقرأ بيانات من تيار الإدخال القياسي stdin‎
2) تقرأ بيانات من تيار الملف ‎stream‎
3) تقرأ البيانات من سلسلة الحروف المنتهية بـ ‎'\0'‎ المسماة ‎buffer‎. الوصول إلى نهاية السلسة يعدل الوصول لنهاية الملف في ‎fscanf‎

محتويات

[تعديل] المعطيات

stream - تيار الإدخال الذي ستتم منه القراءة
buffer - مؤشر إلى سلسلة من الحروف منتهية بـ‎‎'\0'‎ ستتم القراءة منها
format - مؤشر إلى سلسلة من الحروف منتهية بـ‎‎'\0'‎ توضح التنسيق (طريقة فهم النص).

The format string consists of whitespace characters (any single whitespace character in the format string consumes all available consecutive whitespace characters from the input), non-whitespace characters except % (each such character in the format string consumes exactly one identical character from the input) and conversion specifications. Each conversion specification has the following format:

  • introductory % character
  • (اختياري) assignment-suppressing character *. If this option is present, the function does not assign the result of the conversion to any receiving argument.
  • (اختياري) integer number (greater than zero) that specifies maximum field width, that is, the maximum number of characters that the function is allowed to consume when doing the conversion specified by the current conversion specification. Note that %s and %[ may lead to buffer overflow if the width is not provided.
  • (اختياري) length modifier that specifies the size of the receiving argument, that is, the actual destination type. This affects the conversion accuracy and overflow rules. The default destination type is different for each conversion type (see table below).
  • conversion format specifier

The following format specifiers are available:

Conversion
specifier
Explanation Argument type
length modifier ‎hh‎ ‎h‎ (none) l ll j z t L
‎%‎ matches literal % غ\م غ\م غ\م غ\م غ\م غ\م غ\م غ\م غ\م
‎c‎
matches a character

If a width specifier is used, matches exactly width characters (the argument must be a pointer to an element of an array of char in that case, with room for at least width characters). Unlike %s and %[, does not append the null character to the array.

غ\م غ\م
char*
wchar_t*
غ\م غ\م غ\م غ\م غ\م
‎s‎
matches a sequence of non-whitespace characters (a string)

If width specifier is used, matches up to width or until the first whitespace character, whichever appears first. Always stores a null character in addition to the characters matched (so the argument array must have room for at least width+1 characters)

‎[‎set‎]‎
matches a non-empty sequence of character from set of characters.

If the first character of the set is ‎^‎, then all characters not in the set are matched. If the set begins with ‎]‎ or ‎^]‎ then the ‎]‎ character is also included into the set. It is implementation-defined whether the character ‎-‎ in the non-initial position in the scanset may be indicating a range, as in ‎[0-9]‎. If width specifier is used, matches only up to width. Always stores a null character in addition to the characters matched (so the argument array must have room for at least width+1 characters)

‎d‎
matches a decimal integer.

The format of the number is the same as expected by strtol() with the value 10 for the ‎base‎ argument

signed char* or unsigned char*
signed short* or unsigned short*
signed int* or unsigned int*
signed long* or unsigned long*
signed long long* or unsigned long long*
intmax_t* or uintmax_t*
size_t*
ptrdiff_t*
غ\م
‎i‎
matches an integer.

The format of the number is the same as expected by strtol() with the value 0 for the ‎base‎ argument (base is determined by the first characters parsed)

‎u‎
matches a unsigned integer.

The format of the number is the same as expected by strtoul() with the value 0 for the ‎base‎ argument (base is determined by the first characters parsed)

‎o‎
matches an octal integer.

The format of the number is the same as expected by strtol() with the value 8 for the ‎base‎ argument

‎x‎
matches an hexadecimal integer.

The format of the number is the same as expected by strtol() with the value 16 for the ‎base‎ argument

‎n‎
returns the number of characters read so far.

No input is consumed. Does not increment the assignment count. If the specifier has assignment-suppressing operator defined, the behavior is undefined

‎a‎, ‎A‎
‎e‎, ‎E‎
‎f‎, ‎F‎
‎g‎, ‎G‎
matches a floating-point number.

The format of the number is the same as expected by strtof()

غ\م غ\م
float*
double*
غ\م غ\م غ\م غ\م
long double*
‎p‎
matches implementation defined character sequence defining a pointer.

‎printf‎ family of functions should produce the same sequence using %p format specifier

غ\م غ\م
void**
غ\م غ\م غ\م غ\م غ\م غ\م

All conversion specifiers other than ‎[‎, ‎c‎, and ‎n‎ consume and discard all leading whitespace characters before attempting to parse the input. These consumed characters do not count towards the specified maximum field width.

The conversion specifiers ‎lc‎, ‎ls‎, and ‎l[‎ perform multibyte-to-wide character conversion as if by calling mbrtowc‎ with an mbstate_t‎ object initialized to zero before the first character is converted.

The conversion specifiers ‎s‎ and ‎[‎ always store the null terminator in addition to the matched characters. The size of the destination array must be at least one greater than the specified field width.

The correct conversion specifications for the fixed-width character types (int8_t‎, etc) are defined in the header <cinttypes>.


... - المعطيات التي سيتم التخزين فيها

[تعديل] القيمة المُرجعة

1-3) عدد المعطيات التي تم اسناد قيمة اليها بنجاح أو EOF‎ في حالة حدوث خطأ في القراءة قبل اسناد أي قيم.

[تعديل] ملحوظات

Because most conversion specifiers first consume all consecutive whitespace, code such as

scanf("%d", &a);
scanf("%d", &b);

will read two integers that are entered on different lines (second %d will consume the newline left over by the first) or on the same line, separated by spaces or tabs (second %d will consume the spaces or tabs).

The conversion specifiers that do not consume leading whitespace, such as %c, can be made to do so by using a whitespace character in the format string:
scanf("%d", &a);
scanf(" %c", &c); // ignore the endline after %d, then read a char

[تعديل] مثال

#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
#include <stddef.h>
#include <locale.h>
 
int main(void)
{
    int i, j;
    float x, y;
    char str1[10], str2[4];
    wchar_t warr[2];
    setlocale(LC_ALL, "en_US.utf8");
 
    char input[] = "25 54.32E-1 Thompson 56789 0123 56ß水";
    /* parse as follows:
       %d: an integer
       %f: a floating-point value
       %9s: a string of at most 9 non-whitespace characters
       %2d: two-digit integer (digits 5 and 6)
       %f:  a floating-point value (digits 7, 8, 9)
       %*d: an integer which isn't stored anywhere
       ' ': all consecutive whitespace
       %3[0-9]: a string of at most 3 decimal digits (digits 5 and 6)
       %2lc: two wide characters, using multibyte to wide conversion  */
    int ret = sscanf(input, "%d%f%9s%2d%f%*d %3[0-9]%2lc",
                     &i, &x, str1, &j, &y, str2, warr);
 
    printf("Converted %d fields:\ni = %d\nx = %f\nstr1 = %s\n"
           "j = %d\ny = %f\nstr2 = %s\n"
           "warr[0] = U+%x warr[1] = U+%x\n",
           ret, i, x, str1, j, y, str2, warr[0], warr[1]);
 
#ifdef __STDC_LIB_EXT1__
    int n = sscanf_s(input, "%d%f%s", &i, &x, str1, (rsize_t)sizeof str1);
    // writes 25 to i, 5.432 to x, the 9 bytes "thompson\0" to str1, and 3 to n.
#endif
}

الخرج:

Converted 7 fields:
i = 25
x = 5.432000
str1 = Thompson
j = 56
y = 789.000000
str2 = 56
warr[0] = U+df warr[1] = U+6c34

[تعديل] أنظر أيضا

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تطبع خرج منسق في stdout‎ أو تيار ملف أو Buffer
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