why is not the following working?

purpleburple · 09-14-2002, 10:32 PM

Hi. What am I doing wrong?

#include <stdio.h>

int main(void)
{

char choice[20];

puts("Would you like to continue?\n");
puts("Enter \'yes\' or \'no\'");
scanf("%s", &choice);

if (choice == "YES" || choice == "yes")
printf("We are continuing!\n");

else if (choice == "NO" || choice == "no"){
printf("We are ending the program!\n");
}
else{
printf("You did not respond correctly!\n");
}

return 0;

}

I enter 'yes' ...
and it just prints >
You did not respond correctly!
I thought I was supposed to enclose the tests in double quotes.

thanks

acid_kewpie · 09-15-2002, 03:43 AM

well like we have already told you, you can't compare strings using mathematical operators like ==. like we already said, use strcmp() or whatever

purpleburple · 09-15-2002, 10:31 PM

thanks .... sorry. If I wanted to write my own strcmp function just to see how it works I think I could search thru the array and compare each character with the user entered array to see if it's a match and give an error if it isn't.

Is my idea close at all to how strcmp works? and where could I get a book or reference to how each of the various C functions like strcmp work and their function definitions? I think learning these would open up alot about C to me.

thanks again

llama_meme · 09-16-2002, 11:13 AM

That's pretty much how strcmp works, although it doesn't just return a boolean, it returns the number of characters by which the two string differ. Therefore when two strings match exactly, strcmp returns 0.

Alex

verigoth · 09-16-2002, 12:15 PM

what you might want to do instead would be:

if((choice[0]=='Y') || (choice[0]=='y'))

that way lazy people like me can just hit one char

verigoth

TheLinuxDuck · 09-18-2002, 08:58 AM

I would also suggest that if you insist on using scanf, please include a length operator on the %s, so that buffer overruns are not possible, as:

Code:

scanf("%20s", &choice);

A better option is to use fgets, IMHO, since it requires a length. Something like this works really nicely:

Code:

void getInput(char *myInput, const short int len)
{
  int dummy, sLen;
  fgets(myInput, len, stdin);
  sLen = strlen(myInput) - 1;
  if(myInput[sLen] =='\n') myInput[sLen] = '\0';
  else while((dummy = fgetc(stdin)) != '\n');
}

Since fgets leaves the newline on the input, we check to see if it exists.. if it does, we trim it off, if not, we know that there is still some input left in the input buffer, so we slurp it out into a dummy variable and poof, we're set.