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  1. #include<stdio.h>
  2. #include<string.h>
  3.  
  4. int main()
  5. {
  6.     char id[50];
  7.     int i, len;
  8.     int valid = 1;
  9.  
  10.     scanf("%s", id);    
  11.     len = strlen(id);
  12.  
  13.     if( !( (id[0]>='a' && id[0]<='z') || (id[0]>='A' && id[0]<='Z') || id[0]=='_' ) )
  14.     {
  15.         valid = 0;
  16.     }
  17.  
  18.     for(i=1; i<len; i++)
  19.     {
  20.         if( !( (id[i]>='a' && id[i]<='z') || (id[i]>='A' && id[i]<='Z') || (id[i]>='0' && id[i]<='9') || id[i]=='_' ) )
  21.         {
  22.             valid = 0;
  23.             break;
  24.         }
  25.     }
  26.  
  27.     if(valid==1)
  28.     {
  29.         printf("%s is a valid identifier\n", id);
  30.     }
  31.     else
  32.     {
  33.         printf("%s is not a valid identifier\n", id);
  34.     }
  35.  
  36.     return 0;
  37. }
Success #stdin #stdout 0s 5332KB
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stdin
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my-var
stdout
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my-var is not a valid identifier
https://ideone.com/H6e0Kw
language:
C (gcc 8.3)
created:
7 days ago
visibility:
public

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