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Algorithms Algorithms（算法） bsearch bsearch_s qsort qsort_s Atomic operations Atomic operations library（原子操作庫） 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（線程圍欄） ATOMIC_VAR_INIT kill_dependency memory_order（內(nèi)存排序） C keywords auto（自動存儲） break（跳出循環(huán)） C keywords（關鍵詞） case char const（常量修飾符） continue default（預設運算式） do double（雙精度浮點型） else enum（枚舉類型） extern（全局變量） float（浮點數(shù)） for fortran goto（goto語句） if（if語句） inline（行內(nèi)函式） int long（長整型） register（寄存器變量） restrict（ restrict類型限定符） return short signed sizeof（sizeof運算符） static（靜態(tài)變量） struct（結(jié)構(gòu)體） switch（switch語句） typedef（typedef關鍵字） union（聯(lián)合體） unsigned（無符號） void（空類型） volatile（volatile變量） while（while語句） _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（對齊指定符） Alternative operators and tokens（替代運算符和令牌） Analyzability Arithmetic operators Arithmetic types Array declaration（數(shù)組聲明） Array initialization（陣列初始化） ASCII Chart Assignment operators（賦值運算符） types（atomic類型限定符） Basic concepts Bit fields（位域） break statement C language C Operator Precedence cast operator character constant（字符字面量） Comments（注釋符） Comparison operators（比較運算符） compound literals（符合字面量） Conditional inclusion（條件包含） Conformance（一致性） const type qualifier（const 限定符） Constant expressions（常量表達） continue statement Declarations（聲明） do-while loop Enumerations（枚舉類型） Escape sequences（轉(zhuǎn)義字符） Expressions（表達式） External and tentative definitions（外部和暫定的定義） File scope（文件范圍） floating constant（浮點常量） for loop Function declarations（函數(shù)聲明） Function definitions（函數(shù)聲明） Functions Generic selection泛型選擇 goto statement Identifier（標示符） if statement Implicit conversions（隱式轉(zhuǎn)換） Increment/decrement operators（前置/后置操作符） Initialization（初始化） inline function specifier（內(nèi)聯(lián)函式） integer constant Lifetime（生命期） Logical operators（邏輯運算符） Lookup and name spaces Main function（主函式） Member access operators（會員接入運營商） Memory model Objects and alignment（字節(jié)對齊） Order of evaluation（評估順序） Other operators Phases of translation（翻譯階段） Pointer declaration Preprocessor（預處理） restrict type qualifier（restrict類型限定符） return statement Scalar initialization（標量類型初始化） Scope（范圍） sizeof operator（sizeof運算符） Statements（陳述） static assert declaration（靜態(tài)斷言聲明） Static storage duration（靜態(tài)存儲周期） Storage-class specifiers（存儲類說明符） string literals（字符串字面量） Struct and union initialization（結(jié)構(gòu)體與聯(lián)合體初始化） Struct declaration（結(jié)構(gòu)體聲明） switch statement Thread storage duration（線程存儲時間） Type Type（類型） Typedef declaration（Typedef聲明） Undefined behavior（未定義行為） Union declaration（聯(lián)合體聲明） Value categories（值類別） Variadic arguments（變長參數(shù)宏） volatile type qualifier（volatile 類型限定符） while loop _Alignof operator _Noreturn function specifier Date and time asctime（asctime函數(shù)） asctime_s clock CLOCKS_PER_SEC clock_t ctime（ctime函數(shù)） ctime_s Date and time utilities（日期和時間庫） difftime（計算兩個時間的間隔） gmtime gmtime_s localtime localtime_s mktime（將時間結(jié)構(gòu)數(shù)據(jù)轉(zhuǎn)換成經(jīng)過的秒數(shù)的函數(shù)） strftime（格式化輸出時間函數(shù)） time timespec timespec_get time_t tm wcsftime（格式化時間寬字符） Dynamic memory management aligned_alloc C memory management library（內(nèi)存管理庫） calloc free（釋放動態(tài)分配空間的函數(shù)） malloc（動態(tài)分配內(nèi)存空間的函數(shù)） realloc（重新分配內(nèi)存空間的函數(shù)） Error handling abort_handler_s assert（斷言） constraint_handler_t errno（錯誤報告） Error handling（錯誤處理） Error numbers（錯誤個數(shù)） ignore_handler_s set_constraint_handler_s static_assert File input/output clearerr（清除/復位） fclose feof ferror fflush（清空文件緩沖區(qū)） 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
characters

在頭文件<stdio.h>中定義




(1)


int scanf（const char * format，...）;

（直到C99）


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

（自C99以來）



(2)


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

（直到C99）


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

（自C99以來）



(3)


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

（直到C99）


int sscanf（const char *限制緩沖區(qū)，const char *限制格式，...）;

（自C99以來）


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

(4)

（自C11以來）

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

(5)

（自C11以來）

int sscanf_s（const char *限制緩沖區(qū)，const char *限制格式，...）;

(6)

（自C11以來）

從各種來源讀取數(shù)據(jù)，根據(jù)其解釋并將format結(jié)果存儲到給定位置。

1）從中讀取數(shù)據(jù) stdin

2）從文件流中讀取數(shù)據(jù) stream

3）從空終止的字符串中讀取數(shù)據(jù)buffer。到達字符串的末尾等同于達到文件結(jié)束條件fscanf

4-6）與（1-3）相同，不同之處在于%c，%s和%[轉(zhuǎn)換說明符每個都需要兩個參數(shù)（通常的指針和rsize_t表示接收數(shù)組大小的類型值，當使用％c讀取時可能為1成一個字符），除了在運行時檢測到以下錯誤并調(diào)用當前安裝的約束處理函數(shù)：

  • 指針類型的任何參數(shù)都是空指針

  • format，stream或者buffer是空指針

  • ％c，％s或％[，加上終止空字符，將會超過為每個轉(zhuǎn)換說明符提供的第二個（rsize_t）參數(shù)所寫的字符數(shù)

  • 可選地，還有任何其他可檢測到的錯誤，例如未知的轉(zhuǎn)換說明符

由于所有的邊界檢查功能，scanf_s，fscanf_s，和sscanf_s僅保證可供如果__STDC_LIB_EXT1__由實現(xiàn)所定義，并且如果用戶定義__STDC_WANT_LIB_EXT1__的整數(shù)常數(shù)1，包括之前<stdio.h>。

參數(shù)

流

-

輸入文件流從中讀取



















































































緩沖

-

指向以null結(jié)尾的字符串讀取的指針



















































































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 speci?ed ?eld 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 ?rst 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-?le, 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 *或uintmax_t *

為size_t *

ptrdiff_t的*

N / A











































































一世

匹配一個整數(shù)。數(shù)字的格式與strtol（）所期望的相同，基本參數(shù)的值為0（基數(shù)由解析的第一個字符決定）。




















































































在

匹配一個無符號的十進制整數(shù)。數(shù)字的格式與strtoul（）的預期相同，基本參數(shù)的值為10。




















































































該

匹配一個無符號的八進制整數(shù)。數(shù)字的格式與strtoul（）的預期相同，基本參數(shù)的值為8。




















































































x，X

匹配一個無符號的十六進制整數(shù)。數(shù)字的格式與strtoul（）預期的基本參數(shù)的值為16相同。




















































































?

返回迄今閱讀的字符數(shù)。沒有輸入被消耗。不增加分配計數(shù)。如果說明符具有定義的分配抑制運算符，則行為是未定義的。




















































































a，A（C99）e，E f，F(xiàn) g，G

匹配一個浮點數(shù)。數(shù)字的格式與strtof（）的預期相同。

N / A

N / A

浮動*

雙*

N / A

N / A

N / A

N / A

長雙*











































































p

匹配定義指針的實現(xiàn)定義的字符序列。printf系列函數(shù)應該使用％p格式說明符產(chǎn)生相同的序列。

N / A

N / A

無效**

N / A

N / A

N / A

N / A

N / A

N / A











































































...

-

接收參數(shù)



















































































對于每個轉(zhuǎn)換說明符以外的n，最長的輸入字符序列不超過任何指定的字段寬度，或者正是轉(zhuǎn)換說明符所期望的或者是期望序列的前綴，是流中消耗的內(nèi)容。在消耗序列之后的第一個字符（如果有的話）仍然未讀。如果消耗的序列長度為零或消費的序列無法如上所述進行轉(zhuǎn)換，則會發(fā)生匹配失敗，除非文件結(jié)束，編碼錯誤或讀取錯誤阻止來自流的輸入，在這種情況下，它是輸入失敗。

在嘗試解析輸入之前，除了[，，之外的所有轉(zhuǎn)換說明符c并n消耗并放棄所有前導空白字符（如同調(diào)用isspace一樣確定）。這些消耗的字符不會計入指定的最大字段寬度。

轉(zhuǎn)換說明符lc，ls并l[執(zhí)行多字節(jié)到寬字符的轉(zhuǎn)換，就好像通過調(diào)用mbrtowc（）并在轉(zhuǎn)換第一個字符之前將mbstate_t對象初始化為零一樣。

除了匹配的字符之外，轉(zhuǎn)換說明符s并[始終存儲空終止符。目標數(shù)組的大小必須至少比指定的字段寬度大1。使用％小號或％[，而不指定目的地的陣列大小，是為不安全作為得到

為正確的轉(zhuǎn)換規(guī)格固定寬度整數(shù)類型（int8_t等）都在頭中定義<inttypes.h>還（雖然SCNdMAX，SCNuMAX等是同義詞%jd，%ju等）。

每個轉(zhuǎn)換說明符的操作之后都有一個序列點 ; 這允許將多個字段存儲在相同的“匯”變量中。

當解析一個不帶數(shù)字的指數(shù)結(jié)束的不完整浮點值時，例如用轉(zhuǎn)換說明符％f解析“100er”時，會消耗序列“100e”（可能有效的浮點數(shù)的最長前綴） ，導致匹配錯誤（消耗的序列不能轉(zhuǎn)換為浮點數(shù)），并保留“r”?，F(xiàn)有的實現(xiàn)不遵循這個規(guī)則并回滾到只消耗“100”，留下“er”，例如glibc bug 1765

如果轉(zhuǎn)換規(guī)范無效，則行為未定義。

...

-

接收參數(shù)


返回值

1-3）成功分配的接收參數(shù)數(shù)量（EOF如果在分配第一個接收參數(shù)之前發(fā)生匹配故障，則可能為零），或者在分配第一個接收參數(shù)前發(fā)生輸入故障。

4-6）與（1-3）相同，但是EOF如果存在運行時約束沖突，也會返回。

注意

由于大多數(shù)轉(zhuǎn)換說明符首先消耗所有連續(xù)的空白，所以代碼如。

scanf("%d", &a);scanf("%d", &b);

將讀取在不同行上輸入的兩個整數(shù)（第二個％d將使用第一個剩下的換行符）或在同一行上，由空格或制表符分隔（第二個％d將使用空格或制表符）。不使用前導空格的轉(zhuǎn)換說明符（如％c）可以通過在格式字符串中使用空格字符來完成：

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 56?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}

輸出：

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

參考

  • C11標準（ISO / IEC 9899：2011）：

    • 7.21.6.2 fscanf函數(shù)（p：317-324）

    • 7.21.6.4 scanf函數(shù)（p：325）

    • 7.21.6.7 sscanf函數(shù)（p：326）

    • K.3.5.3.2 fscanf_s函數(shù)（p：592-593）

    • K.3.5.3.4 scanf_s函數(shù)（p：594）

    • K.3.5.3.7 sscanf_s函數(shù)（p：596）

  • C99標準（ISO / IEC 9899：1999）：

    • 7.19.6.2 fscanf函數(shù)（p：282-289）

    • 7.19.6.4 scanf函數(shù)（p：290）

    • 7.19.6.7 sscanf函數(shù)（p：291）

  • C89 / C90標準（ISO / IEC 9899：1990）：

    • 4.9.6.2 fscanf函數(shù)

    • 4.9.6.4 scanf函數(shù)

    • 4.9.6.6 sscanf函數(shù)

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