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Algorithms Algorithms（算法） bsearch bsearch_s qsort qsort_s Atomic operations Atomic operations library（原子操作库） ATOMIC_*_LOCK_FREE atomic_compare_exchange_strong atomic_compare_exchange_strong_explicit atomic_compare_exchange_weak atomic_compare_exchange_weak_explicit atomic_exchange atomic_exchange_explicit atomic_fetch_add atomic_fetch_add_explicit atomic_fetch_and atomic_fetch_and_explicit atomic_fetch_or atomic_fetch_or_explicit atomic_fetch_sub atomic_fetch_sub_explicit atomic_fetch_xor atomic_fetch_xor_explicit atomic_flag atomic_flag_clear atomic_flag_clear_explicit ATOMIC_FLAG_INIT atomic_flag_test_and_set atomic_flag_test_and_set_explicit atomic_init atomic_is_lock_free atomic_load atomic_load_explicit atomic_signal_fence atomic_store atomic_store_explicit atomic_thread_fence（线程围栏） ATOMIC_VAR_INIT kill_dependency memory_order（内存排序） C keywords auto（自动存储） break（跳出循环） C keywords（关键词） case char const（常量修饰符） continue default（预设运算式） do double（双精度浮点型） else enum（枚举类型） extern（全局变量） float（浮点数） for fortran goto（goto语句） if（if语句） inline（行内函式） int long（长整型） register（寄存器变量） restrict（ restrict类型限定符） return short signed sizeof（sizeof运算符） static（静态变量） struct（结构体） switch（switch语句） typedef（typedef关键字） union（联合体） unsigned（无符号） void（空类型） volatile（volatile变量） while（while语句） _Alignas _Alignof _Atomic _Bool _Complex _Generic _Imaginary _Noreturn _Static_assert _Thread_local C language #define directive #elif directive #else directive #endif directive #error directive #if directive #ifdef directive #ifndef directive #include directive #line directive #pragma directive alignas（对齐指定符） Alternative operators and tokens（替代运算符和令牌） Analyzability Arithmetic operators Arithmetic types Array declaration（数组声明） Array initialization（阵列初始化） ASCII Chart Assignment operators（赋值运算符） types（atomic类型限定符） Basic concepts Bit fields（位域） break statement C language C Operator Precedence cast operator character constant（字符字面量） Comments（注释符） Comparison operators（比较运算符） compound literals（符合字面量） Conditional inclusion（条件包含） Conformance（一致性） const type qualifier（const 限定符） Constant expressions（常量表达） continue statement Declarations（声明） do-while loop Enumerations（枚举类型） Escape sequences（转义字符） Expressions（表达式） External and tentative definitions（外部和暂定的定义） File scope（文件范围） floating constant（浮点常量） for loop Function declarations（函数声明） Function definitions（函数声明） Functions Generic selection泛型选择 goto statement Identifier（标示符） if statement Implicit conversions（隐式转换） Increment/decrement operators（前置/后置操作符） Initialization（初始化） inline function specifier（内联函式） integer constant Lifetime（生命期） Logical operators（逻辑运算符） Lookup and name spaces Main function（主函式） Member access operators（会员接入运营商） Memory model Objects and alignment（字节对齐） Order of evaluation（评估顺序） Other operators Phases of translation（翻译阶段） Pointer declaration Preprocessor（预处理） restrict type qualifier（restrict类型限定符） return statement Scalar initialization（标量类型初始化） Scope（范围） sizeof operator（sizeof运算符） Statements（陈述） static assert declaration（静态断言声明） Static storage duration（静态存储周期） Storage-class specifiers（存储类说明符） string literals（字符串字面量） Struct and union initialization（结构体与联合体初始化） Struct declaration（结构体声明） switch statement Thread storage duration（线程存储时间） Type Type（类型） Typedef declaration（Typedef声明） Undefined behavior（未定义行为） Union declaration（联合体声明） Value categories（值类别） Variadic arguments（变长参数宏） volatile type qualifier（volatile 类型限定符） while loop _Alignof operator _Noreturn function specifier Date and time asctime（asctime函数） asctime_s clock CLOCKS_PER_SEC clock_t ctime（ctime函数） ctime_s Date and time utilities（日期和时间库） difftime（计算两个时间的间隔） gmtime gmtime_s localtime localtime_s mktime（将时间结构数据转换成经过的秒数的函数） strftime（格式化输出时间函数） time timespec timespec_get time_t tm wcsftime（格式化时间宽字符） Dynamic memory management aligned_alloc C memory management library（内存管理库） calloc free（释放动态分配空间的函数） malloc（动态分配内存空间的函数） realloc（重新分配内存空间的函数） Error handling abort_handler_s assert（断言） constraint_handler_t errno（错误报告） Error handling（错误处理） Error numbers（错误个数） ignore_handler_s set_constraint_handler_s static_assert File input/output clearerr（清除/复位） fclose feof ferror fflush（清空文件缓冲区） fgetc fgetpos fgets fgetwc fgetws File input/output fopen fopen_s fprintf fprintf_s fputc fputs fputwc fputws fread freopen freopen_s fscanf fscanf_s fseek fsetpos ftell fwide fwprintf fwprintf_s fwrite fwscanf fwscanf_s getc getchar gets gets_s getwchar perror printf printf_s putc putchar puts putwc putwchar remove rename rewind scanf scanf_s setbuf setvbuf snprintf sprintf sscanf sscanf_s swprintf swprintf_s swscanf swscanf_s tmpfile tmpfile_s tmpnam tmpnam_s ungetc ungetwc vfprintf vfprintf_s vfscanf vfscanf_s vfwprintf vfwprintf_s vfwscanf vfwscanf_s vprintf vprintf_s vscanf vscanf_s vsnprintf vsprintf vsscanf vsscanf_s vswprintf vswprintf_s vswscanf vswscanf_s vwprintf vwprintf_s vwscanf vwscanf_s wprintf wprintf_s wscanf wscanf_s Localization support lconv LC_ALL LC_COLLATE LC_CTYPE LC_MONETARY LC_NUMERIC LC_TIME localeconv Localization support setlocale Numerics abs acos acosf acosh acoshf acoshl acosl asin asinf asinh asinhf asinhl asinl atan atan2 atan2f atan2l atanf atanh atanhf atanhl atanl cabs cabsf cabsl cacos cacosf cacosh cacoshf cacoshl cacosl carg cargf cargl casin casinf casinh casinhf casinhl casinl catan catanf catanh catanhf catanhl catanl cbrt cbrtf cbrtl ccos ccosf ccosh ccoshf ccoshl ccosl ceil ceilf ceill cexp cexpf cexpl cimag cimagf cimagl clog clogf clogl CMPLX CMPLXF CMPLXL Common mathematical functions complex Complex number arithmetic conj conjf conjl copysign copysignf copysignl cos cosf cosh coshf coshl cosl cpow cpowf cpowl cproj cprojf cprojl creal crealf creall csin csinf csinh csinhf csinhl csinl csqrt csqrtf csqrtl ctan ctanf ctanh ctanhf ctanhl ctanl div double_t erf erfc erfcf erfcl erff erfl exp exp2 exp2f exp2l expf expl expm1 expm1f expm1l fabs fabsf fabsl fdim feclearexcept fegetenv fegetexceptflag fegetround feholdexcept feraiseexcept fesetenv fesetexceptflag fesetround fetestexcept feupdateenv FE_ALL_EXCEPT FE_DFL_ENV FE_DIVBYZERO FE_DOWNWARD FE_INEXACT FE_INVALID FE_OVERFLOW FE_TONEAREST FE_TOWARDZERO FE_UNDERFLOW FE_UPWARD Floating-point environment float_t floor floorf floorl fma fmaf fmal fmax fmaxf fmaxl fmin fminf fminl fmod fmodf fmodl fpclassify FP_INFINITE FP_NAN FP_NORMAL FP_SUBNORMAL FP_ZERO frexp frexpf frexpl HUGE_VAL HUGE_VALF HUGE_VALL hypot hypotf hypotl I ilogb ilogbf ilogbl imaginary imaxabs imaxdiv INFINITY isfinite isgreater isgreaterequal isinf isless islessequal islessgreater isnan isnormal isunordered labs ldexp ldexpf ldexpl ldiv lgamma lgammaf lgammal llabs lldiv llrint llrintf llrintl llround llroundf llroundl log log10 log10f log10l log1p log1pf log1pl log2 log2f log2l logb logbf logbl logf logl lrint lrintf lrintl lround lroundf lroundl MATH_ERREXCEPT math_errhandling MATH_ERRNO modf modff modfl nan NAN nanf nanl nearbyint nearbyintf nearbyintl nextafter nextafterf nextafterl nexttoward nexttowardf nexttowardl Numerics pow powf powl Pseudo-random number generation rand RAND_MAX remainder remainderf remainderl remquo remquof remquol rint rintf rintl round roundf roundl scalbln scalblnf scalblnl scalbn scalbnf scalbnl signbit sin sinf sinh sinhf sinhl sinl sqrt sqrtf sqrtl srand tan tanf tanh tanhf tanhl tanl tgamma tgammaf tgammal trunc truncf truncl Type-generic math _Complex_I _Imaginary_I Program support abort atexit at_quick_exit exit EXIT_FAILURE EXIT_SUCCESS getenv getenv_s jmp_buf longjmp Program support utilities quick_exit raise setjmp SIGABRT SIGFPE SIGILL SIGINT signal SIGSEGV SIGTERM sig_atomic_t SIG_DFL SIG_ERR SIG_IGN system _Exit Strings atof atoi atol atoll btowc c16rtomb c32rtomb char16_t char32_t isalnum isalpha isblank iscntrl isdigit isgraph islower isprint ispunct isspace isupper iswalnum iswalpha iswblank iswcntrl iswctype iswdigit iswgraph iswlower iswprint iswpunct iswspace iswupper iswxdigit isxdigit mblen mbrlen mbrtoc16 mbrtoc32 mbrtowc mbsinit mbsrtowcs mbsrtowcs_s mbstate_t mbstowcs mbstowcs_s mbtowc memchr memcmp memcpy memcpy_s memmove memmove_s memset memset_s Null-terminated byte strings Null-terminated multibyte strings Null-terminated wide strings strcat strcat_s strchr strcmp strcoll strcpy strcpy_s strcspn strerror strerrorlen_s strerror_s Strings library strlen strncat Thread support call_once cnd_broadcast cnd_destroy cnd_init cnd_signal cnd_timedwait cnd_wait mtx_destroy mtx_init mtx_lock mtx_plain mtx_recursive mtx_timed mtx_timedlock mtx_trylock mtx_unlock once_flag ONCE_FLAG_INIT thrd_busy thrd_create thrd_current thrd_detach thrd_equal thrd_error thrd_exit thrd_join thrd_nomem thrd_sleep thrd_success thrd_timedout thrd_yield Thread support library thread_local tss_create tss_delete TSS_DTOR_ITERATIONS tss_get tss_set Type support Boolean type support library Fixed width integer types FLT_EVAL_METHOD FLT_ROUNDS max_align_t NULL Numeric limits offsetof ptrdiff_t size_t Type support Variadic functions Variadic functions va_arg va_copy va_end va_list va_start

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在头文件<stdio.h>中定义




(1)


int scanf（const char * format，...）;

（直到C99）


int scanf（const char * restrict format，...）;

（自C99以来）



(2)


int fscanf（FILE * stream，const char * format，...）;

（直到C99）


int fscanf（FILE * restrict stream，const char * restrict format，...）;

（自C99以来）



(3)


int sscanf（const char * buffer，const char * format，...）;

（直到C99）


int sscanf（const char *限制缓冲区，const char *限制格式，...）;

（自C99以来）


int scanf_s（const char * restrict format，...）;

(4)

（自C11以来）

int fscanf_s（FILE * restrict stream，const char * restrict format，...）;

(5)

（自C11以来）

int sscanf_s（const char *限制缓冲区，const char *限制格式，...）;

(6)

（自C11以来）

从各种来源读取数据，根据其解释并将format结果存储到给定位置。

1）从中读取数据 stdin

2）从文件流中读取数据 stream

3）从空终止的字符串中读取数据buffer。到达字符串的末尾等同于达到文件结束条件fscanf

4-6）与（1-3）相同，不同之处在于%c，%s和%[转换说明符每个都需要两个参数（通常的指针和rsize_t表示接收数组大小的类型值，当使用％c读取时可能为1成一个字符），除了在运行时检测到以下错误并调用当前安装的约束处理函数：

  • 指针类型的任何参数都是空指针

  • format，stream或者buffer是空指针

  • ％c，％s或％[，加上终止空字符，将会超过为每个转换说明符提供的第二个（rsize_t）参数所写的字符数

  • 可选地，还有任何其他可检测到的错误，例如未知的转换说明符

由于所有的边界检查功能，scanf_s，fscanf_s，和sscanf_s仅保证可供如果__STDC_LIB_EXT1__由实现所定义，并且如果用户定义__STDC_WANT_LIB_EXT1__的整数常数1，包括之前<stdio.h>。

参数

流

-

输入文件流从中读取



















































































缓冲

-

指向以null结尾的字符串读取的指针



















































































格式

-

pointer to a null-terminated character string specifying how to read the input. The format string consists of.   non-whitespace multibyte characters except %: each such character in the format string consumes exactly one identical character from the input stream, or causes the function to fail if the next character on the stream does not compare equal.   whitespace characters: any single whitespace character in the format string consumes all available consecutive whitespace characters from the input (determined as if by calling isspace in a loop). Note that there is no difference between "\n", " ", "\t\t", or other whitespace in the format string.   conversion specifications. Each conversion specification has the following format:    introductory % character   (optional) assignment-suppressing character *. If this option is present, the function does not assign the result of the conversion to any receiving argument.   (optional) 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.   (optional) 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 (C99).   h   (none)   l   ll (C99).   j (C99).   z (C99).   t (C99).   L     %   matches literal %   N/A   N/A   N/A   N/A   N/A   N/A   N/A   N/A   N/A     c    matches a character or a sequence of characters  If a width specifier is used, matches exactly width characters (the argument must be a pointer to an array with sufficient room). Unlike %s and %[, does not append the null character to the array.   N/A   N/A   char*   wchar_t*   N/A   N/A   N/A   N/A   N/A     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*   N/A     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 an unsigned decimal integer.  The format of the number is the same as expected by strtoul() with the value 10 for the base argument.     o   matches an unsigned octal integer.  The format of the number is the same as expected by strtoul() with the value 8 for the base argument.     x, X   matches an unsigned hexadecimal integer.  The format of the number is the same as expected by strtoul() 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(C99) e, E f, F g, G   matches a floating-point number.  The format of the number is the same as expected by strtof().   N/A   N/A   float*   double*   N/A   N/A   N/A   N/A   long double*     p   matches implementation defined character sequence defining a pointer.  printf family of functions should produce the same sequence using %p format specifier.   N/A   N/A   void**   N/A   N/A   N/A   N/A   N/A   N/A    For every conversion specifier other than n, the longest sequence of input characters which does not exceed any specified field width and which either is exactly what the conversion specifier expects or is a prefix of a sequence it would expect, is what's consumed from the stream. The first character, if any, after this consumed sequence remains unread. If the consumed sequence has length zero or if the consumed sequence cannot be converted as specified above, the matching failure occurs unless end-of-file, an encoding error, or a read error prevented input from the stream, in which case it is an input failure. All conversion specifiers other than [, c, and n consume and discard all leading whitespace characters (determined as if by calling isspace) 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 use of %s or %[, without specifying the destination array size, is as unsafe as gets. The correct conversion specifications for the fixed-width integer types (int8_t, etc) are defined in the header <inttypes.h> (although SCNdMAX, SCNuMAX, etc is synonymous with %jd, %ju, etc). There is a sequence point after the action of each conversion specifier; this permits storing multiple fields in the same "sink" variable. When parsing an incomplete floating-point value that ends in the exponent with no digits, such as parsing "100er" with the conversion specifier %f, the sequence "100e" (the longest prefix of a possibly valid floating-point number) is consumed, resulting in a matching error (the consumed sequence cannot be converted to a floating-point number), with "r" remaining. Existing implementations do not follow this rule and roll back to consume only "100", leaving "er", e.g. glibc bug 1765.

Conversion specifier

Explanation

Argument type

length modifier

hh (C99).

h

(none)

l

ll (C99).

j (C99).

z (C99).

t (C99).

L

%

matches literal %

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

c

matches a character or a sequence of characters  If a width specifier is used, matches exactly width characters (the argument must be a pointer to an array with sufficient room). Unlike %s and %[, does not append the null character to the array.

N/A

N/A

char*

wchar_t*

N/A

N/A

N/A

N/A

N/A

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*

N/A

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 an unsigned decimal integer.  The format of the number is the same as expected by strtoul() with the value 10 for the base argument.

o

matches an unsigned octal integer.  The format of the number is the same as expected by strtoul() with the value 8 for the base argument.

x, X

matches an unsigned hexadecimal integer.  The format of the number is the same as expected by strtoul() 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(C99) e, E f, F g, G

matches a floating-point number.  The format of the number is the same as expected by strtof().

N/A

N/A

float*

double*

N/A

N/A

N/A

N/A

long double*

p

matches implementation defined character sequence defining a pointer.  printf family of functions should produce the same sequence using %p format specifier.

N/A

N/A

void**

N/A

N/A

N/A

N/A

N/A

N/A

Conversion specifier

Explanation

Argument type



















































































length modifier

hh (C99).

h

(none)

l

ll (C99).

j (C99).

z (C99).

t (C99).

L












































































%

matches literal %

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A











































































c

matches a character or a sequence of characters  If a width specifier is used, matches exactly width characters (the argument must be a pointer to an array with sufficient room). Unlike %s and %[, does not append the null character to the array.

N/A

N/A

char*

wchar_t*

N/A

N/A

N/A

N/A

N/A











































































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*

N/A











































































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 an unsigned decimal integer.  The format of the number is the same as expected by strtoul() with the value 10 for the base argument.




















































































o

matches an unsigned octal integer.  The format of the number is the same as expected by strtoul() with the value 8 for the base argument.




















































































x, X

matches an unsigned hexadecimal integer.  The format of the number is the same as expected by strtoul() 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（C99）e，E f，F g，G

匹配一个浮点数。数字的格式与strtof（）的预期相同。

N / A

N / A

浮动*

双*

N / A

N / A

N / A

N / A

长双*











































































p

匹配定义指针的实现定义的字符序列。printf系列函数应该使用％p格式说明符产生相同的序列。

N / A

N / A

无效**

N / A

N / A

N / A

N / A

N / A

N / A











































































...

-

接收参数



















































































  • 非空白多字节字符除外%：格式字符串中的每个这样的字符只消耗输入流中的一个完全相同的字符，或者如果流中的下一个字符不相等，则会导致函数失败。

  • 空白字符：格式字符串中的任何单个空白字符都会消耗输入中所有可用的连续空白字符（如同通过调用isspace循环来确定）。请注意，有没有什么区别"\n"，" "，"\t\t"在格式字符串或其他空白。

  • 转换规格。每个转换规范具有以下格式：

    • 介绍%人物

    • （可选）分配抑制字符*。如果存在此选项，则函数不会将转换结果分配给任何接收参数。

    • （可选）指定最大字段宽度的整数数字（大于零），即该函数在执行由当前转换规范指定的转换时允许使用的最大字符数。请注意，如果未提供宽度，％s和％[可能会导致缓冲区溢出。

    • （可选）长度修饰符，用于指定接收参数的大小，即实际的目标类型。这会影响转换精度和溢出规则。每种转换类型的默认目标类型都不相同（请参阅下表）。

    • 转换格式说明符

以下格式说明符可用：

Conversion

说明符说明参数类型长度修饰符    hh（C99）。

h   (none)   l   ll (C99).

j (C99).

z (C99).

t (C99).

L %   匹配字面%   N / AN / AN / AN / AN / AN / AN / AN / AN / A      c    一个匹配字符或序列字符如果使用宽度说明，完全匹配宽度的字符（参数必须是一个指针数组有足够的空间）。与％s和％[不同，不会将空字符追加到数组。

N/A   N/A   char*

wchar_t*

N / AN / AN / AN / AN / A      s    匹配非空白字符序列（字符串）如果使用宽度说明符，则匹配宽度或直到第一个空白字符，以先出现者为准。除了匹配的字符外，总是存储一个空字符（所以参数数组必须至少有宽度+ 1个字符的空间）。

 `[`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()`](../string/byte/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`](../types/integer)`*` or [`uintmax_t`](../types/integer)`*`

size_t*

ptrdiff_t*

N / A      i   匹配整数。数的格式是相同的通过按预期strtol()与值0的base参数（基部由解析的第一字符确定）。

 `u`   matches an unsigned **decimal integer**.  The format of the number is the same as expected by [`strtoul()`](../string/byte/strtoul) with the value `10` for the `base` argument.
 `o`   matches an unsigned **octal integer**.  The format of the number is the same as expected by [`strtoul()`](../string/byte/strtoul) with the value `8` for the `base` argument.
 `x`, `X`   matches an unsigned **hexadecimal integer**.  The format of the number is the same as expected by [`strtoul()`](../string/byte/strtoul) 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`(C99)

e, E

f, F

g，G   匹配一个浮点数。数字的格式与预期的相同strtof()。

N/A   N/A   float*

double*

N/A   N/A   N/A   N/A   long double*

 `p`   matches implementation defined character sequence defining a **pointer**.  `printf` family of functions should produce the same sequence using `%p` format specifier.

N/A   N/A   void**

n不适用不适用不适用不适用不适用不适用不适用不适用于任何指定字段宽度的最长输入字符序列的   每个转换说明符，或者正是转换说明符所期望的或者是它期望的顺序是从流中消耗的。在消耗序列之后的第一个字符（如果有的话）仍然未读。如果消耗的序列长度为零或消费的序列不能如上所述进行转换，则会发生匹配失败，除非文件结束，编码错误或读取错误阻止了来自流的输入，在这种情况下，它是输入失败。

在尝试解析输入之前，除了[，，之外的所有转换说明符都会消耗并放弃所有前导空白字符（如同通过调用一样确定）。这些消耗的字符不会计入指定的最大字段宽度。cnisspace

转换说明符lc，ls并l[执行多字节到宽字符转换，就好像通过在第一个字符转换之前使用初始化为零mbrtowc()的mbstate_t对象调用一样。

除了匹配的字符之外，转换说明符s并[始终存储空终止符。目标数组的大小必须至少比指定的字段宽度大1。在不指定目标数组大小的情况下，使用%s或%[不安全gets。

对于固定宽度的整数类型（正确的转换规格int8_t<inttypes.h>还（虽然，等等）都在头定义SCNdMAX，SCNuMAX等是同义词%jd，%ju等）。

每个转换说明符的操作之后都有一个序列点; 这允许将多个字段存储在相同的“汇”变量中。

在解析指数中不包含数字的不完整浮点值时（例如"100er"使用转换说明符进行解析），会消耗%f序列"100e"（可能有效的浮点数的最长前缀），从而导致匹配错误（消耗的序列不能转换为浮点数），"r"剩余的。现有的实现不遵循此规则并仅回滚消耗"100"，只留下"er"例如glibc错误1765。

 ...   -   receiving arguments

返回值

1-3）成功分配的接收参数数量（EOF如果在分配第一个接收参数之前发生匹配故障，则可能为零），或者在分配第一个接收参数前发生输入故障。

4-6）与（1-3）相同，但是EOF如果存在运行时约束冲突，也会返回。

注意

由于大多数转换说明符首先消耗所有连续的空白，所以代码如。

scanf("%d", &a);scanf("%d", &b);

将读取在不同行上输入的两个整数（第二个％d将使用第一个剩下的换行符）或在同一行上，由空格或制表符分隔（第二个％d将使用空格或制表符）。不使用前导空格的转换说明符（如％c）可以通过在格式字符串中使用空格字符来完成：

scanf("%d", &a);scanf(" %c", &c); // ignore the endline after %d, then read a char

例

#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}

输出：

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

参考

  • C11标准（ISO / IEC 9899：2011）：

    • 7.21.6.2 fscanf函数（p：317-324）

    • 7.21.6.4 scanf函数（p：325）

    • 7.21.6.7 sscanf函数（p：326）

    • K.3.5.3.2 fscanf_s函数（p：592-593）

    • K.3.5.3.4 scanf_s函数（p：594）

    • K.3.5.3.7 sscanf_s函数（p：596）

  • C99标准（ISO / IEC 9899：1999）：

    • 7.19.6.2 fscanf函数（p：282-289）

    • 7.19.6.4 scanf函数（p：290）

    • 7.19.6.7 sscanf函数（p：291）

  • C89 / C90标准（ISO / IEC 9899：1990）：

    • 4.9.6.2 fscanf函数

    • 4.9.6.4 scanf函数

    • 4.9.6.6 sscanf函数

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