Help with simple encode program

This is a simple casear cipher encode only portion that i wrote. it:

1. Promtps for user input
2. Asks for the shift value
3. Uses the shift value such as 2 on the first letter then increments it by 1 for each letter after that.
EXAMPLE: Hello would be Jhpqu


My problem is at the end of each encrypted word it prints a funny character that i dont need. How can i eliminate it??thanks

Code:

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


   



/*encode function, to encode user input */
int main()
{
	char buff[BUFSIZ];
	int i = 0;
	int shift_value;
	int p = 0;

    printf( "**initializing.....**\n\n"
	        "**linking..........**\n\n");
	printf( "Welcome agent Brown\n\n");
	printf( "You have accessed the Caesar Cipher program\n\n");
	printf("\nPlease enter the text you wish to encrypt: ");/*accept user input */
	fgets(buff, sizeof(buff), stdin);

	
	printf("\nEnter your encryption shift value (anything from +-1 to 25): "); 
    scanf ("%i", &shift_value);

	{	
			while ( buff[i] != '\0'  )
			{
				
				buff[i] = buff[i] + shift_value + i++;
				
				 }
		
	}

	printf("\n Your encrypted text is:%s\n",buff);/*return encrypted text */

	
	return 0; /* indicate successful completeion */
}

Remove the newline.

[edit] Curses, foiled again! [/edit]


Quzah.

I said that already!

http://faq.cprogramming.com/cgi-bin/...&id=1043284385

No, see my link.

oh the wonders of being a noob. I tried adjusting the code in the link and utilizing it in my code in different parts, but now it doesnt return anything. i dont get any text back now.

Code:

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


   



/*encode function, to encode user input */
int main()
{
	char buff[BUFSIZ];
	int i = 0;
	int shift_value;
	int p = 0;
	char *r;

    printf( "**initializing.....**\n\n"
	        "**linking..........**\n\n");
	printf( "Welcome agent Brown\n\n");
	printf( "You have accessed the Caesar Cipher program\n\n");
	printf("\nPlease enter the text you wish to encrypt: ");/*accept user input */
	fgets(buff, sizeof(buff), stdin);

	
	printf("\nEnter your encryption shift value (anything from +-1 to 25): "); 
    scanf ("%i", &shift_value);

	{	
			while ( buff[i] != '\0'  )
			{
				
				buff[i] = buff[i] + shift_value + i++;
				
				 }
		
	}
	if (fgets(buff, sizeof(buff), stdin) != NULL)
	{
		if ((r = strchr(buff, '\n')) != NULL)
		*r = '\0';

		printf("\nYour encrypted text is:%s\n",buff);/*return encrypted text */

	}
	return 0; /* indicate successful completeion */
}

Shouldn't you be removing the newline from the buffer before you shift it?


Quzah.

arg, yes, and i just noticed this line i have in there.

Code:

while ( buff[i] != '\0'  )

thats evidently not going to work anymore.
How could i take that out or modify it and get the code to work?

Well, you could go until buff[i] was '\n' instead...

hmm this is what i have now. the character at the end from the newline is gone but now the first 2 letters are funny shapes??

Code:

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


   



/*encode function, to encode user input */
int main()
{
	char buff[BUFSIZ];
	int i = 0;
	int shift_value;
	int p = 0;
	char *r;

    printf( "**initializing.....**\n\n"
	        "**linking..........**\n\n");
	printf( "Welcome agent Brown\n\n");
	printf( "You have accessed the Caesar Cipher program\n\n");
	printf("\nPlease enter the text you wish to encrypt: ");/*accept user input */
	fgets(buff, sizeof(buff), stdin);
	if (fgets(buff, sizeof(buff), stdin) != NULL)
	{
		if ((r = strchr(buff, '\n')) != NULL)
		*r = '\0';
	}


	
	printf("\nEnter your encryption shift value (anything from +-1 to 25): "); 
    scanf ("%i", &shift_value);

	{	
			while ( buff[i] != '\n'  )
			{
				
				buff[i] = buff[i] + shift_value + i++;
				
				 }
		
	}
	
		printf("\nYour encrypted text is:%s\n",buff);/*return encrypted text */

	
	return 0; /* indicate successful completeion */
}

All you need to do is pay attention to what it is you're really doing, rather than just keep changing small seemingly random portions of your code in hope you stumble across whatever it is that really isn't working right. Look:

Code:

fgets(buff, sizeof(buff), stdin);
	if (fgets(buff, sizeof(buff), stdin) != NULL)
	{
		if ((r = strchr(buff, '\n')) != NULL)
		*r = '\0';
	}

1 - Fill the line with something.
2 - Fill it again with something else, and then, remove the newline from that line of text.

Why? Why are you getting two lines of text here?

Code:

while ( buff[ i ] != '\n'  )
			{
				
				buff[ i ] = buff[ i ] + shift_value + i++;

1 - A for loop would be better, because then you're actually initializing i right before you use it, so you don't have to wonder what's in it.
2 - You have already removed the newline character in the code above, so why are you trying to go until you find one?

See? All you need to do is pay attention to what it is you're actually doing.

Quzah.

> buff[i] = buff[i] + shift_value + i++;
You'd be much better off if you didn't have undefined operations in your code either.

Just simplify to
buff[i] = buff[i] + shift_value + i;
i++;

i do have the habit of jumping ahead of myself without paying attention. This is just so overwhelming right now. Hopefully with more practice i can not fret so much about writing these programs.

I understand the for loop makes more sense. But what would i be checking for, i have tested a few ideas to no avail. I either get back no text, or 1 funny character.

Code:

	{	
		for(??? )
			{

			  buff[i] = buff[i] + shift_value + i;
			  i++;
				
			}
		
	}

Code:

buff[i] = buff[i] + shift_value + i;

is unlikely to produce the result that you want.

• you're not rotating, just "shifting" the character value up
• the amount that you're "shifting" the character code by increases as the loop progresses

If this is for a homework assignment, I'm sure that you've been introduced to the character type functions, or at least to the ASCII character set. If you add, say, 13 to the character "z", you get a character code that is not a letter.

Which means, in effect, that you need what is called modulo maths, which is maths modulo number of letters in your alphabet. Formula for shifting one letter:

result = c - offset + shift mod(%) number of letters + offset

offset is how far from 0 your alphabet numbering starts. c is your character to shift. number of letters is number of letter in alphabet.

You subtract the offset to make it as if your numbering started at 0, add the shift value, and modulo by the number of letters to wrap is your result exceeds them (Not sure how % operator reacts if in x % y, y is bigger than x.). Then you add offset back on to get your new character.