1. WIKI教程
2. C标准库
3. int isalnum(int c)

int isalnum(int c)

描述 (Description)

C库函数void isalnum(int c)检查传递的字符是否为字母数字。

声明 (Declaration)

以下是isalnum（）函数的声明。

int isalnum(int c);

参数 (Parameters)

• c - 这是要检查的字符。

返回值 (Return Value)

如果c是数字或字母，则此函数返回非零值，否则返回0。

例子 (Example)

以下示例显示了isalnum（）函数的用法。

#include <stdio.h>
#include <ctype.h>
int main () {
   int var1 = 'd';
   int var2 = '2';
   int var3 = '\t';
   int var4 = ' ';
   if( isalnum(var1) ) {
      printf("var1 = |%c| is alphanumeric\n", var1 );
   } else {
      printf("var1 = |%c| is not alphanumeric\n", var1 );
   }
   if( isalnum(var2) ) {
      printf("var2 = |%c| is alphanumeric\n", var2 );
   } else {
      printf("var2 = |%c| is not alphanumeric\n", var2 );
   }
   if( isalnum(var3) ) {
      printf("var3 = |%c| is alphanumeric\n", var3 );
   } else {
      printf("var3 = |%c| is not alphanumeric\n", var3 );
   }
   if( isalnum(var4) ) {
      printf("var4 = |%c| is alphanumeric\n", var4 );
   } else {
      printf("var4 = |%c| is not alphanumeric\n", var4 );
   }
   return(0);
}

让我们编译并运行上面的程序，产生以下结果 -

var1 = |d| is alphanumeric
var2 = |2| is alphanumeric
var3 = |        | is not alphanumeric
var4 = | | is not alphanumeric