escape sequence

I would like to make an error appear when a user hits enter instead of entering data first (ie. leaving the line blank). I have tried
line[i] == '' generates an error
line[i] == ' ' only works if they hit the spacebar first
line[i] == '\0' or EOF or '\r' or '\f' none of which work...

my first instinct is to use '\n' but obviously that wouldnt work.

So if there isnt an escape sequence for this, what would be the best way? Count the number of characters and if that number > 0 then error?

How are you reading the input in the first place?

If you're using fgets(), then the answer is easy

Code:

char buff[100];
if ( fgets( buff, sizeof(buff), stdin ) != NULL ) {
  if ( buff[0] == '\n' ) {
    // user just pressed return
  } else {
    // mmm, something's in the buffer, better see what they typed
  }
}

yes it is getting passed in via fgets but then sent to a validate function where I check to make sure the input is within all the paramaters (ie... (a - n) etc)

If I must keep it in main then I will but I would really like to have this in the function where it would make more sense.

thats where this is used
if( line[i] == '\n' )
return TRUE; //this needs to be here or else everything entered returns as FALSE

ok did get salems code to work, but is there anyway to get the same thing accomplished within the function?

here is the full function:

Code:

 static int valid( char array[], int maxnum )
{   
	int i = 0, decCount = 0, negCount = 0;

	for( i = 0; i < maxnum; i++)
	{
		if( array[i] == '\n' )
			return BOOL_TRUE;

		if( array[i] == NULL )  // **THIS IS THE PROBLEM.**
			return BOOL_FALSE;

		if(( array[i] < '0' || array[i] > '9' ) && array[i] != '.'&& array[i] != '-')
			return BOOL_FALSE;

		if( array[i] == '-' && i > 0) // '-' can only be first element of array
			return BOOL_FALSE;
		
		if( array[i] == '.' )
			decCount++;
		if( decCount > 1)  // only allow 1 decimal
			return BOOL_FALSE;
	}

	return BOOL_TRUE;
}

>if( array[i] == NULL ) // **THIS IS THE PROBLEM.**
what are you trying to test for here? did you mean
>>if( array[i] == '\0' )

i *think* i understand what you're asking. see modified code

Code:

static int valid( char array[], int maxnum )
{   
	int i = 0, decCount = 0, negCount = 0;

	for( i = 0; i < maxnum; i++)
	{
		if( array[i] == '\n')
			if (i > 0)
				return BOOL_TRUE;
			else
				return BOOL_FALSE;
		
		if( array[i] == NULL )  // **THIS IS THE PROBLEM.**
			return BOOL_FALSE;
		
		if(( array[i] < '0' || array[i] > '9' ) && array[i] != '.'&& array[i] != '-')
			return BOOL_FALSE;

		if( array[i] == '-' && i > 0) // '-' can only be first element of array
			return BOOL_FALSE;
		
		if( array[i] == '.' )
			decCount++;
		if( decCount > 1)  // only allow 1 decimal
			return BOOL_FALSE;
	}

	return BOOL_TRUE;
}

Sorry if I was too vague.

Thanks for your help!

Originally posted by RyeDunn
Sorry if I was too vague.

Thanks for your help!

the problem was of course, that the \n is always at the end, whether or not there's stuff before it.

Originally posted by moi


the problem was of course, that the \n is always at the end, whether or not there's stuff before it.

.... unless fgets() reads a buffer full of data, in which case the last character won't be \n.