Thread: Alteration of chars of a string

So i want the user to input a string, and then reverse the capps. So "echHis" turns "into ECHhIS".

I have no clue what to do because the book I read didn't civer this. I tried using strcmp() but it only does full strings not a character in a string i.e.: int = strcmp(str1[3],"a");

How can I compare a specific char in a string to a given char or even a char from another string? I just want a function or a tutorial

Thanks!

Thanks oogabooga, those are exactly the functions I needed for this specific program.

However, I see some application in the way I am approaching it (what if i am looking for a char inside of a string but don't want it to be upper/lower case).

Here is how I written it so far. I need something along the lines of: strcpy(temp[i],abc[a]);

Thanks!

Code:

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

int main()
{
    char start [50];
    int sizeStart;

    char abc[53] = {"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"};
    char ABC[53] = {"ABCDEFGHIJKLMNOPKRSTUVWXYZabcdefghijklmnopqrstuvwxyz"};

    int i = 0;
    int a = 0;

    int compare;


    printf("Input a string to reverse the case: ");
    scanf("%s", start);

    sizeStart = strlen (start);

printf("size of start is %d\n", sizeStart);

    while(i<=sizeStart)
    {
        a = 0;
        while(a<=51)
        {
            compare = strcmp(start[i],abc[a]);

            if(compare == 0)
            {
                strcpy(start[i],ABC[a]);
            }

            a++;

        }
        i++;
    }


printf("New String is: %s", start);

    return 0;
}

Oh, so something like this?

Code:

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

int main()
{
    char start [50];
    int sizeStart;

    char abc[53] = {"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"};
    char ABC[53] = {"ABCDEFGHIJKLMNOPKRSTUVWXYZabcdefghijklmnopqrstuvwxyz"};

    int i = 0;
    int a = 0;

    int compare;


    printf("Input a string to reverse the case: ");
    scanf("%s", start);

    sizeStart = strlen (start);

printf("size of start is %d\n", sizeStart);

    while(i<=sizeStart)
    {
        a = 0;
        while(a<=51)
        {
            if(start[i] == abc[a])
            {
                start[i] = ABC[a];
            }

            a++;

        }
        i++;
    }


printf("New String is: %s", start);

    return 0;
}

I know I am missing something very basic here. Think I am doing the "start[i] = ABC[a];" wrong... Warning! Thick skull!

EDIT: Oh, perhaps when it changes it to capps, it check for capps and changes it back to lower case. I'll need some sort of break in there, researchign it now.

Didn't need some sort fo break, i needed break XD I thought break will break out of all the nested loops, not just one. Lucky me! Thanks all for your help much appreciated.

As for the concern of the 49 length of start. Doesn't matter it is just an exercise, not a real app.

As for the "while(a<=51)" i did that bc in my head when i set up "char abc[53]" that gives me 52 chars to work with.

The while loop started with 0 (because as i understand the string starts at 0, so if it goes up to 51 that gives 52 chars

also i tested it out with a string of "a-z" and it works, so I guess the computer made sense of it.

Ah ASCII values, never thought of that. Great idea probably faster too! I'll have to keep that in mind when making other programs!

The declaration of the 2 arrays abc and ABC is not good, what you do is undefined, remove the braces:

Code:

char abc[]="..."
char ABC[]="..."

And second, starting with the code from post#6, you need to add a break statement after successfully changing a character:

Code:

if(...==...) {
  ...
  break;
}

At last, replace <=51 with <sizeof(abc)-1.