C program- using switch causing infinite loop

I wrote the program to keep looping as long as a user entered numerical input. When the appropriate "End program" is used, the program terminates. If a user entered 9 for example, the program would say error and ask them to re-enter. However, it goes into an infinite loop when a user enters a character, such as p. How do I correct this? I want it to read the same error line.

Here it is:

#include <stdio.h>
#include <stdlib.h>

int main()
{
int input;

do
{
printf ("1. You chose a square\n");
printf ("2. You chose a triangle\n");
printf ("3. You chose a circle\n");
printf ("4. You chose a rectangle\n");
printf ("5. End the program\n");
printf( "Enter your selection: \n\n" );
scanf( "%d", &input );
switch ( input )
{
case 1: /* Prints the selection chosen by the user*/
printf("You chose a square\n\n");
break;
case 2:
printf("You chose a triangle\n\n");
break;
case 3:
printf("You chose a circle\n\n");
break;
case 4:
printf("You chose a rectangle\n\n");
break;
case 5:
printf( "End the program\n" );
default:
printf("Error: Please re-enter your selection\n");
}
}while(input != 5);

system("PAUSE");
}

Don't use scanf() for user input. Use fgets() and parse the string instead.

To parse the string you can use strtol(), or sscanf(), or a myriad other methods.

Like the previous poster stated, you could parse your input.



The above is just a quick example of what you might do.

How do I incorporate this into the program? Have it before the switch loop?

scanf reads from stdin.
so does fgets(buffer,length,stdin)
Oh, you'd better find your own reference for fgets.


oops, you'd better investigate sscanf. It's already known that I'm less familiar with the return values of scanf/printf functions than one would hope.
A reference that, by title, looks promising.

I am Just start learn C program this post all programming language like very much.

Do you have a clear idea of what you're trying to do? Usually, using switch isn't the best way of doing it.

Regards,

Shaun.

Interesting, because switch was suggested by my instructor as the best way to do it. I want to avoid stream errors and only have the 5 numbers be considered valid input.

In my experience, academics like switch case because it makes their assignments more readable and easier to mark. But from the original code, I'd reckon that you'd get an error if you enter a character other than a number.

You could do an if( input<1 || input>5 ) first and report the error there. And if you're going to use while like that, you need do ... while I think.

Edit: Sorry, you were using do ... while - you hadn't lined up your code properly, so I missed it.

Regards,

Shaun.