isalnum() 函数定义在 ctype.h 头文件中。它有助于检查指定字符是否为字母数字。如果字符是字母或数字，则称其为字母数字。
int isalnum(int argument); #where argument will be a character
isalnum() 函数接受一个参数。
| 参数 | 描述 | 必需/可选 |
|---|---|---|
| 参数 | 要检查的字符 | 必需 |
返回值为 1 或 0。
| 输入 | 返回值 |
|---|---|
| 参数是字母数字 | 1 |
| 参数既不是字母也不是数字 | 0 |
#include <stdio.h>
#include <ctype.h>
int main()
{
char ch;
int output;
ch = '10';
output = isalnum(ch);
printf("If %c is passed, return value is %d\n", ch, output);
ch = 'A';
output = isalnum(ch);
printf("If %c is passed, return value is %d\n", ch, output);
ch = 'B';
output = isalnum(ch);
printf("If %c is passed, return value is %d\n", ch, output);
ch = '+';
output = isalnum(ch);
printf("If %c is passed, return value is %d\n", ch, output);
return 0;
}
输出
If 10 is passed, return value is 1 If A is passed, return value is 1 If B is passed, return value is 1 If + is passed, return value is 0
#include <stdio.h>
#include <ctype.h>
int main()
{
char ch;
printf("Enter a character: ");
scanf("%c", &ch);
if (isalnum(ch) == 0)
printf("The given %c is not an alphanumeric character.", ch);
else
printf("The given %c is an alphanumeric character.", ch);
return 0;
}
输出
Enter a character: 0 The given 0 is an alphanumeric character.
