Thread: Problems Running a Caesar Cipher

Hello forums. I was making some adjustments to a Caesar Cipher to allow for it to read a .txt file. However, after having saved the file in numerous places, including the directory where Code:Blocks is saved, I was still not able to get it to work. Can someone please take a look at my code and tell me if the code actually works?

Code:

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


void main()
{
    int shift, i;
    char code[30];


    FILE*fp;


    fp=fopen("caesarText","r");


    if(fp ==NULL){ printf("Error opening input file \"caesarText\"!\n");
    return 0;
   }
    else{
    printf("Enter how much you would like to shift the text: /n");
    scanf("%d", &shift);
        {
            for(i=0;i<strlen(code);i++)
            {       if(code[i]==' '){}
                    else
                    {
                        if (code[i]>='x')
                        {
                        code[i]=code[i]-26;
                        }
                        code[i]=code[i]+shift;
                    }
            }


    }
    printf("Your encrypted text is: %s", code);
    getch();}
}

If by not getting it to work you mean you are getting the "Error opening input file" message indicating that the file can't be found:

With Codeblocks I normally chuck any files in the project folder for the specific project I'm working on and they are found no problem. Depending on your system you may need the .txt filetype appended to the filename though.

I have the file saved in C drive ,program files x86, same place that code blocks in saved in. It is still not working.

Can I ask a favor and have someone run this program with a text file to see if it actually works. The text file just has to be a semtence.

Do you happen to know where I might have saved my EXE ? Sorry I am new to computer programming. I really appreciate the help.

While your problem can most likely be fixed by taking the advice in post #3 there are several steps you can take to determine where your text file should be located and also give you a better idea of why the file opening failed.

Probably the easiest solution would be to open a file for writing that has an unique file name because by default opening a file for writing has fewer chances of failure. If the file opens correctly then you will need to use your operating system's find functionality to locate exactly where this uinque file is located. You then place your file in that directory. Normally when running the program in Code::Blocks the default directory is the directory that contains the project files.

And when you check that the file properly opened you can use perror() to possibly tell you why the file failed to open.

Jim

While your problem can most likely be fixed by taking the advice in post #3 there are several steps you can take to determine where your text file should be located and also give you a better idea of why the file opening failed.

Probably the easiest solution would be to open a file for writing that has an unique file name because by default opening a file for writing has fewer chances of failure. If the file opens correctly then you will need to use your operating system's find functionality to locate exactly where this uinque file is located. You then place your file in that directory. Normally when running the program in Code::Blocks the default directory is the directory that contains the project files.

And when you check that the file properly opened you can use perror() to possibly tell you why the file failed to open.

Jim

Ok , i've noticed that even after the need for the .txt extension in your filename is sorted, the program is also missing an important line. The code below is still pretty "basic" and will only allow you to read the first line of the file but will at least give you the chance to experiment a bit.

Code:

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

int main(void)
{
    int shift, i;
    char code[30];
    FILE*fp;

    fp=fopen("caesarText.txt","r");

    if(fp ==NULL)
    {
        printf("Error opening input file \"caesarText\"!\n");
    }
    else
    {
        printf("Enter how much you would like to shift the text: ");
        scanf("%d", &shift);
        fgets(code,30,fp);          // important line missing in original code

        for(i=0;i < strlen(code);i++)
        {
            if(code[i]==' ')
            {

            }
            else
            {
                if (code[i]>='x')
                {
                    code[i]=code[i]-26;
                }
                code[i]=code[i]+shift;
            }
        }

        printf("Your encrypted text is: %s", code);

    }
    getchar();
    return 0;
}