isalnum

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头文件：#include <ctype.h>

isalnum() 用来判断一个字符是否为英文字母或数字，相当于 isalpha(c) || isdigit(c)，其原型为：
int isalnum(int c);

【参数】c 为需要检测的字符。

【返回值】若参数c 为字母或数字，若 c 为 0 ~ 9 a ~ z A ~ Z 则返回非 0，否则返回 0。

注意，isalnum()为宏定义，非真正函数。

【实例】找出str 字符串中为英文字母或数字的字符。

复制纯文本新窗口

#include <ctype.h> 
main(){ 
char str[] = "123c@#FDsP[e?"; 
int i; 
for (i = 0; str[i] != 0; i++) 
if(isalnum(str[i])) 
printf("%c is an alphanumeric character\n", str[i]); 
}

#include <ctype.h>main(){    char str[] = "123c@#FDsP[e?";    int i;    for (i = 0; str[i] != 0; i++)        if(isalnum(str[i]))            printf("%c is an alphanumeric character\n", str[i]);}

输出结果：
1 is an apphabetic character
2 is an apphabetic character
3 is an apphabetic character
c is an apphabetic character
F is an apphabetic character
D is an apphabetic character
s is an apphabetic character
P is an apphabetic character
e is an apphabetic character

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