Thread: always prints ASCII character 255

I am passing a string through an external validation function (that I wrote and was working previously) and the function is correctly picking up all the errors, but when I enter the correct input and printf the result to the screen it prints the ASCII character of 255 (y with two dots above it). It does this no matter what number I put in and because of the ASCII value I have a feeling it has something to do with my buffer size of 256? When I changed the buffer size to 1256 (just to troubleshoot) it printed nothing to the screen when there was correct input and carried on to the next step.

When I change the printf sign to %s it returns segmentation fault

Here is my code;

Code:

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

char *validate(char *valid);

int main(void)
{
	char    buffer1[256], buffer2[256], buffer3[256];
	char    *input_1, *input_2, *input_3; 
        char    *valid_1, *valid_2, *valid_3;

	printf("Please enter input 1.\n");
	input_1 = fgets(buffer1, 256, stdin);
	
	valid_1 = validate(input_1);
	printf("valid_1 is %c\n", valid_1);

	printf("Please enter input 2.\n");
	input_2 = fgets(buffer2, 256, stdin);
	
	valid_2 = validate(input_2);
	printf("valid_2 is %c\n", valid_2);
	
	printf("Please enter input 3.\n");
	input_3 = fgets(buffer3, 256, stdin);
	
	valid_3 = validate(input_3);
	printf("valid_3 is %c\n", valid_3);
	
	return(0);
}


char *validate(char *valid)
{
	char	*valid_input;
	int	length, j, k;
	
	
	length = strlen(valid);
	
	for (k=0; k<length; k++)
	{
		if (valid[k] == '\n')
		{
			valid[k] = '\0';
			length--;
		}
	}
	
	for(j = 0; j < length; j++)
	{
		if (('0' <= valid[j]) && (valid[j] <= '9'))
		{
			continue;
		}
		else if (valid[j] == '.')
		{
			if (j ==0)
			{
				printf("Please enter a number before the dot in your input.\n");
				exit(EXIT_FAILURE);
			}
			else if (j == (length-1))
			{
				printf("Please enter a number after the dot in your input.\n");
				exit(EXIT_FAILURE);
			}
			else
			{
				continue;
			}
		}
		else if (valid[j] == '+')
		{
			if (j == 0)
			{
				continue;
			}
			else
			{
				printf("There is a plus sign in the middle of your entry.\n");
				exit(EXIT_FAILURE);
			}
		}
		else if (valid[j] == '-')
		{
			printf("There is a negative sign in your entry.\n");
			exit(EXIT_FAILURE);
		}
		else
		{
			printf("You have not entered the correct input.\n");
			exit(EXIT_FAILURE);
		}
	}
	
	return(valid_input);
}

In Main:

Where are you allocating memory for these pointers?

Code:

	char    *input_1, *input_2, *input_3; 
        char    *valid_1, *valid_2, *valid_3;

In this function:

Code:

char *validate(char *valid)
{
	char	*valid_input;

Where do you allocate memory for this pointer?


In this snippet:

Code:

	valid_1 = validate(input_1);
	printf("valid_1 is %c\n", valid_1);

You are calling validate() with an uninitialized pointer.

In the printf the "%c" says character but valid_1 is a character pointer.

Thanks guys.

I got rid of all the "input_x" and put in your loop to recalculate the length. Out of interest, when would '\n' not be right before '\0' in this scenario?

I initialised the string (i think) by putting into main

Code:

char *valid_input;

I also changed the external function so it does not return a value and have the function called in main like this;

Code:

fgets(buffer1, 256, stdin);
	
valid_1 = validate(buffer1);
printf("valid_1 is %s\n", valid_1);

Is that what you meant?

I am now getting the correct number printing using %s

Thanks again!!