isalnum() – C函数

C库函数 void isalnum(int c)检查，传递的字符字母是否为数字。

声明

以下是isalnum（）函数的声明。

int isalnum(int c);

参数

• c -- 这是要检查的字符。

返回值

这个函数返回非零值，如果c是一个数字或字母，否则为0

实例

下面的例子显示isalnum（）函数的用法。

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

让我们编译和运行上面的程序，这将产生以下结果：

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