C语言 <ctype.h> isalnum() 函数

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  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。
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  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。
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  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);
  }
  

  尝试一下

  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