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文字

在头文件<ctype.h>中定义



int isalpha(int ch);



检查给定字符是否是字母字符,即大写字母(ABCDEFGHIJKLMNOPQRSTUVWXYZ)或小写字母(abcdefghijklmnopqrstuvwxyz)。

在除“C”以外的语言环境中,字母字符是isupper()或islower()返回true的字符,或者由语言环境认为是字母的任何其他字符。 在任何情况下,iscntrl(),isdigit(),ispunct()和isspace()将为此字符返回false。

如果ch的值不能表示为unsigned char或不等于EOF,则行为是不确定的。

参数

ch

-

分类字符

返回值

如果字符是字母字符,则为非零值,否则为零。

演示使用具有不同区域设置(特定于操作系统)的isalpha()。

#include <ctype.h>#include <stdio.h>#include <locale.h>
 int main(void){
    unsigned char c = '\xdf'; // German letter ß in ISO-8859-1 
    printf("isalpha('\\xdf') in default C locale returned %d\n", !!isalpha(c)); 
    setlocale(LC_CTYPE, "de_DE.iso88591");    printf("isalpha('\\xdf') in ISO-8859-1 locale returned %d\n", !!isalpha(c));}

输出:

isalpha('\xdf') in default C locale returned 0isalpha('\xdf') in ISO-8859-1 locale returned 1

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.4.1.2 isalpha函数(p:200-201)

  • C99标准(ISO / IEC 9899:1999):

    • 7.4.1.2 isalpha函数(p:181-182)

  • C89 / C90标准(ISO / IEC 9899:1990):

    • 4.3.1.2 isalpha函数

扩展内容

iswalpha (C95)

检查宽字符是否为字母(功能)

| 用于isalpha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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