How to clear input buffer after fgets overflow?

问题

I'm facing a little problem with fgets when the input string exceeds its predefined limit.

Taking the example below:

    for(index = 0; index < max; index++)
    {printf(" Enter the %d string : ",index+1)
                if(fgets(input,MAXLEN,stdin))
                {
                    printf(" The string and size of the string is %s and %d \n",input,strlen(input) + 1);
                    removeNewLine(input);
                    if(strcmp(input,"end") != 0)
                   { //Do something with input
                   }
                }

Now when I exceed the length MAXLEN and enter a string, I know that the input will append a '\0' at MAXLEN -1 and that would be it. The problem happens when I try to enter the 2nd string which is not asked for i.e

Output :
Enter the first string : Aaaaaaaaaaaaaaaaaaaa //Exceeds limit
Enter the second string : Enter the third string : ....Waits input

So, I thought I should clear the buffer the standard way as in C. It waits until I enter

return

two times, The first time it being appended to the string and the next time,expecting more input with another return. 1. Is there any method by which I can clear the buffer without entering the extra return? 2. How do I implement error handling for the same? Because the fgets return value will be Non-null and strlen(input) gives me the accepted size of the string by fgets, what should be done?

Thanks a lot

回答1:

If I understood correctly, looks like you want to avoid twice enter press, when entered input is within range.

A work around would be

for(index = 0; index < max; index++)
{
    printf(" Enter the %d th string :",index);
    // if (strlen(input) >=MAXLEN )

    if(fgets(input,MAXLEN,stdin))
    {

        removeNewLine(input);

        if(strcmp(input,"end") != 0)
        // Do something with input 
          ;
    }
    if (strlen(input) == MAXLEN-1 )
      while((ch = getchar())!='\n'  && ch != EOF  );

 }

With a limitation that it will again ask for two times enter when entered characters are exactly MAXLEN-2.

Or else you can simply form your input using character by character input.

回答2:

while ((c=getchar()) != '\n' && c != EOF)
    ;

or:

scanf("%*[^\n]%*c");

来源：https://stackoverflow.com/questions/18348984/how-to-clear-input-buffer-after-fgets-overflow

标签

overflow

fgets