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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

在头文件中定义



char * strerror(int errnum);

(1)


errno_t strerror_s(char * buf,rsize_t bufsz,errno_t errnum);

(2)

(自C11以来)

size_t strerrorlen_s(errno_t errnum);

(3)

(自C11以来)

1)返回一个指向系统错误代码errnum的文本描述的指针,与由perror()打印的描述相同。

errnum通常是从errno变量中获取的,但是该函数接受int类型的任何值。 字符串的内容是特定于语言环境的。

返回的字符串不能被程序修改,但可能会被随后对strerror函数的调用覆盖。 strerror不需要是线程安全的。 实现可能会返回指向静态只读字符串文字的不同指针,或者可能一遍又一遍地返回相同的指针,指向strerror放置字符串的静态缓冲区。

2)与(1)相同,但消息复制到用户提供的存储器buf中。 不超过bufsz-1字节被写入,缓冲区总是空终止的。 如果消息必须被截断以适应缓冲区,并且bufsz大于3,则只写入bufsz-4字节,并且在空终止符之前附加字符“...”。 另外,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:

  • buf是一个空指针

  • bufsz是零或大于RSIZE_MAX

如果写入buf发生在数组的末尾(这可能发生在buf指向的缓冲区的大小小于错误消息中小于bufsz的字符数时可能发生),则行为未定义。

3)计算如果使用errnum调用时,strerror_s会编写的未截断的特定于语言环境的错误消息的长度。 该长度不包括空终止符。 与所有边界检查函数一样,只有在__STDC_LIB_EXT1__由实现定义且用户在包含string.h之前将__STDC_WANT_LIB_EXT1__定义为整数常量1时,strerror_s和strerrorlen_s才能保证可用。

参数

差错编号

-

整数值是指错误代码

BUF

-

指向用户提供的缓冲区的指针

bufsz

-

用户提供的缓冲区大小

返回值

1)指向与errno错误代码errnum相对应的空终止字节字符串。

2)如果整个消息被buf成功存储,则为零,否则为非零。

3)strerror_s将返回的消息的长度(不包括空终止符)

注意

POSIX允许对strerror的后续调用使先前调用返回的指针值无效。 它还指定它是控制这些消息内容的LC_MESSAGES语言环境构面。

strerror_s是唯一允许截断的边界检查函数,因为提供关于失败的尽可能多的信息被认为是更可取的。为了类似的目的,POSIX还定义了strerror_r

#define __STDC_WANT_LIB_EXT1__ 1#include #include #include #include  int main(void){ FILE *fp = fopen(tmpnam((char[L_tmpnam]){0}), "r"); if(fp==NULL) { printf("File opening error: %s\n", strerror(errno)); setlocale(LC_MESSAGES, "de_DE.utf8"); printf("Now in German: %s\n", strerror(errno));#ifdef __STDC_LIB_EXT1__ setlocale(LC_ALL, "zh_CN.utf8"); // printf needs CTYPE for multibyte output size_t errmsglen = strerrorlen_s(errno) + 1; char errmsg[errmsglen]; strerror_s(errmsg, errmsglen, errno); printf("Now in Chinese: %s\n", errmsg);#endif }}

可能的输出:

File opening error: No such file or directory Now in German: Datei oder Verzeichnis nicht gefunden Now in Chinese: 没有那个文件或目录

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.24.6.2 strerror函数(p:371)

    • K.3.7.4.2 strerror_s函数(p:622)

    • K.3.7.4.3 strerrorlen_s函数(p:623)

  • C99标准(ISO / IEC 9899:1999):

    • 7.21.6.2 strerror函数(p:334)

  • C89 / C90标准(ISO / IEC 9899:1990):

    • 4.11.6.2 strerror函数

扩展内容

PERROR

显示当前错误对应的字符串到stderr(函数)

errno

宏扩展到POSIX兼容的线程局部错误号变量(宏变量)

| 用于strerror 的C ++文档|

在头文件中定义



int iswdigit(wint_t ch);


(自C95以来)

检查给定的宽字符是否对应(如果缩小)十个十进制数字字符0123456789中的一个。

参数

CH

-

宽字符

返回值

如果宽字符是数字字符,则为非零值,否则为零。

注意

iswdigitiswxdigit是唯一不受当前安装的C语言环境影响的标准宽字符分类函数。

一些语言环境提供了检测非ASCII数字的附加字符类。

#include #include #include #include  void test(wchar_t a3, wchar_t u3, wchar_t j3){ printf(" '%lc' '%lc' '%lc'\n", a3, u3, j3); printf("iswdigit %d %d %d\n", !!iswdigit(a3), !!iswdigit(u3), !!iswdigit(j3)); printf("jdigit: %d %d %d\n", !!iswctype(a3, wctype("jdigit")), !!iswctype(u3, wctype("jdigit")), !!iswctype(j3, wctype("jdigit")));} int main(void){ wchar_t a3 = L'3'; // the ASCII digit 3 wchar_t u3 = L'三'; // the CJK numeral 3 wchar_t j3 = L'3'; // the fullwidth digit 3 setlocale(LC_ALL, "en_US.utf8"); puts("In American locale:"); test(a3, u3, j3); setlocale(LC_ALL, "ja_JP.utf8"); puts("\nIn Japanese locale:"); test(a3, u3, j3);}

输出:

In American locale: '3' '三' '3'iswdigit 1 0 0jdigit: 0 0 0 In Japanese locale: '3' '三' '3'iswdigit 1 0 0jdigit: 0 0 1

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.30.2.1.5 iswdigit函数(p:449)

  • C99标准(ISO / IEC 9899:1999):

    • 7.25.2.1.5 iswdigit函数(p:395)

扩展内容

isdigit

检查一个字符是否是一个数字(功能)

| 用于iswdigit的C ++文档 |

ASCII 值 (十六进制)

字符

iscntrl iswcntrl.

isprint iswprint.

isspace iswspace.

isblank iswblank.

isgraph iswgraph.

ispunct iswpunct.

isalnum iswalnum.

isalpha iswalpha.

isupper iswupper.

islower iswlower.

isdigit iswdigit.

isxdigit iswxdigit.


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