isalnum

isalnum（测试字符是否为英文或数字）

相关函数：isalpha，isdigit，islower，isupper

表头文件：#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。

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

Linux C

isalnum