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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(guān)鍵詞) case char const(常量修飾符) continue default(預(yù)設(shè)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(guān)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(yù)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(fù)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
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每個C程序編碼在托管執(zhí)行環(huán)境中運行都包含被調(diào)用函數(shù)的定義(不是原型),該函數(shù)main是程序的指定開始。

int main (void) { body }

(1)


int main (int argc, char *argv[]) { body }

(2)


int main (int argc, char *argv[] , other_parameters ) { body }

(3)


/* another implementation-defined signature */

(4)


參數(shù)

ARGC

-

非負值,表示從運行程序的環(huán)境傳遞給程序的參數(shù)數(shù)量。

ARGV

-

指向由空字符結(jié)尾的多字節(jié)字符串組成的指針數(shù)組,這些字符串表示從執(zhí)行環(huán)境(argv0到argvargc-1)傳遞給程序的參數(shù)。argvargc的值保證為0。

body

-

主要功能的主體

other_parameters

-

實現(xiàn)可能允許主函數(shù)的其他形式。一個非常常見的擴展是傳遞char * []類型的第三個參數(shù),指向執(zhí)行環(huán)境變量的指針數(shù)組。

名稱argcargv是任意的,以及參數(shù)類型的表示:int main(int ac, char** av)是同樣有效。

返回值

如果使用return語句,則返回值將用作隱式調(diào)用的參數(shù)exit()(請參閱下面的詳細信息)。值為零并EXIT_SUCCESS表示終止成功,該值EXIT_FAILURE表示不成功終止。

說明

main在所有具有靜態(tài)存儲持續(xù)時間的對象被初始化之后,程序啟動時會調(diào)用該函數(shù)。它是在托管環(huán)境(即操作系統(tǒng))中執(zhí)行的程序的指定入口點。任何獨立程序(引導(dǎo)加載程序,操作系統(tǒng)內(nèi)核等)的入口點的名稱和類型都是實現(xiàn)定義的。

主函數(shù)的雙參數(shù)形式的參數(shù)允許從執(zhí)行環(huán)境傳遞任意多字節(jié)字符串(這些通常稱為命令行參數(shù))。指針argv[1] .. argv[argc-1]指向每個字符串中的第一個字符。argv[0]是一個指向空字符結(jié)尾多字節(jié)字符串的初始字符的指針,它表示用于調(diào)用程序本身的名稱(或者,如果執(zhí)行環(huán)境不支持它,argv0保證為零)。

如果執(zhí)行環(huán)境無法區(qū)分大寫字母和小寫字母,則命令行參數(shù)會轉(zhuǎn)換為小寫字母。

這些字符串是可修改的,任何修改都會一直存在,直到程序終止,盡管這些修改不會傳播回執(zhí)行環(huán)境:例如,可以使用它們strtok。

所指向的數(shù)組的大小argv至少為argc+1,最后一個元素argv[argc]保證為空指針。

main函數(shù)有幾個特殊的屬性:

1)該功能的原型不能由程序提供

2)如果主函數(shù)的返回類型與之兼容int,那么從初始調(diào)用返回到main(但不是從任何后續(xù)遞歸調(diào)用返回)相當于執(zhí)行該exit函數(shù),其值為主函數(shù)作為參數(shù)返回傳遞(然后調(diào)用注冊的函數(shù)atexit,刷新并關(guān)閉所有流,并刪除創(chuàng)建的文件tmpfile,并將控制權(quán)返回給執(zhí)行環(huán)境)。

3)如果主函數(shù)的返回類型與int(eg void main(void))不兼容,則返回到執(zhí)行環(huán)境的值未指定

4)main函數(shù)的主體不需要包含返回語句:如果控制到達main沒有遇到return語句的結(jié)尾,效果就是執(zhí)行return 0;

演示如何通知程序哪里可以找到它的輸入以及在哪里編寫結(jié)果。

Invocation: ./a.out indatafile outdatafile.

#include <stdio.h>
 int main(int argc, char *argv[]){    printf("argc = %d\n", argc);
    int ndx = 0;    while (ndx < argc)    {          printf("argv[%d] --> %s\n", ndx,argv[ndx]);          ++ndx;    }    printf("argv[argc] = %s\n", argv[argc]);    return 0;}

可能的輸出:

argc = 3argv[0] --> ./a.out
argv[1] --> indatafile
argv[2] --> outdatafile
argv[argc] = (null)

參考

  • C11 standard (ISO/IEC 9899:2011):

    • 5.1.2.2.1 Program startup (p: 13)

  • C99 standard (ISO/IEC 9899:1999):

    • 5.1.2.2.1 Program startup (p: 12)

  • C89/C90 standard (ISO/IEC 9899:1990):

    • 2.1.2.2 Hosted environment

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