CODEWITHSUNDEEP
cinputscanf
AustinM
AustinM

Reputation: 803

C input problems

I'm trying to create a simple program in C. Here is kinda what I have so far for the basics

#include <stdio.h>
int main()
{
  char input[256];
  while(1)
  {
    printf("Input: ");
    scanf("%s", input);
    if(strcmp(input, "help") == 0)
      printf("HELP STUFF HERE\n");
    else if(strcmp(input, "1") == 0)
      printf("2\n");
    else if(strcmp(input, "test 1") == 0)
      printf("Test 1\n");
    else if(strcmp(input, "test 2") == 0)
      printf("Test 2\n");
    else
      printf("Error");
    }
  return 0;
}

I'm having some problems though. First of all I can't use spaces. If I try test 1, I get the output of Error. Second problem I'm having is when it outputs Error, it prints it onto the user input prompt

Upvotes: 1

Views: 333

Answers (2)

Jesse Cohen
Jesse Cohen

Reputation: 4040

This is because when you write scanf('%s'), on input test 1 the %s only scans up to the first space and the input your program receives is actually only test.

A useful thing to do in terms of debugging would be to do a 

printf("Error: %s", input)

So you can see what scanf is getting you.

If you just want whole lines of input, fgets() is better to use.

Upvotes: 2

Chris Lutz
Chris Lutz

Reputation: 75389

The simple answer is to change "%s" in scanf to "%[^\n]", which reads all characters other than a newline.

The better answer is to change it to "%255[^\n]", which does the same but includes bounds checking.

The best answer is to use fgets, which doesn't have funky issues with what exactly it will read, or make it difficult to do proper bounds checking.

Upvotes: 3

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