C语言 <ctype.h> isalnum() 函数



  • 描述

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

    如果c是数字或字母,则此函数返回非零值,否则返回0。
    示例
    以下示例显示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述程序,以产生以下结果-
    
    var1 = |d| is alphanumeric
    var2 = |2| is alphanumeric
    var3 = |        | is not alphanumeric
    var4 = | | is not alphanumeric