C语言 isalnum() 函数—测试字符是否为英文或数字

相关函数 isalpha, isdigit, islower, isupper
头文件 #include <ctype.h>
定义函数 int isalnum (int c);
函数说明检查参数 c 是否为英文字母或阿拉伯数字, 在标准c 中相当于使用"isalpha(c) || isdigit(c)"做
测试.
返回值若参数c 为字母或数字, 则返回TRUE, 否则返回NULL(0).
附加说明此为宏定义, 非真正函数.

转自：http://see.xidian.edu.cn/cpp/html/112.html

范例 /* 找出str 字符串中为英文字母或数字的字符 */
#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]);
}
执行 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