Concatenate two characters in c

Question

How to concatenate two characters and store the result in a variable?

For example, I have 3 characters 'a', 'b' and 'c' and I need to join them together and store them in an array and later use this array as a string:

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

char n[10];

main ()
{
    // now I want insert them in an array
    //ex: n = { a + b + c }
}

So store the characters in the appropriate elements of your array, followed by a string terminator. — John Bollinger, Sep 09 '20 at 13:19
Or use `sprintf()` (but that's awfully heavyweight for such a simple task). — John Bollinger, Sep 09 '20 at 13:19
A simple google search might always be helpful. See [How do I ask a good question?](https://stackoverflow.com/help/how-to-ask) — Shivam Jha, Sep 09 '20 at 17:37

ryyker · Answer 1 · 2020-09-09T14:21:28.017

There are many ways, the following 2 methods have exactly the same results: (using your code as a starting point.)

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

int main(void)
{
    //Given the following
    char a = 'a';
    char b = 'b';
    char c = 'c';
    
    // assignment by initializer list at time of creation
    char n1[10] = {a,b,c};
    
    //usage of a string function
    char n2[10] = {0};   //initialize  array
    sprintf(n2, "%c%c%c", a, b, c);

    return 0;
}

Both result in a null terminated char arrays, or C strings.

score 2 · Answer 2 · answered Sep 09 '20 at 13:18

Simply:

char a = 'a', b = 'b', c = 'c';

char str[4];
str[0] = a;
str[1] = b;
str[2] = c;
str[3] = '\0';

Or, if you want str to be stored on the heap (e.g. if you plan on returning it from a function):

char *str = malloc(4);
str[0] = a;
...

Any introductory book on C should cover this.

anastaciu · Answer 3 · 2020-09-09T14:53:28.187

An assignment similar to that can only be done when the char array is declared using array initialiation with a brace-enclosed list:

char a = 'a', b = 'b', c = 'c';
char n[10] = {a, b, c};

After the declaration you can't do it like this because a char array is not a modifiable lvalue:

n = {a, b, c}; //error

To insert characters in an array that has been previously initialized, you need to either insert them one by one as exemplified in another answer, or use some library function like sprintf.

sprintf(n, "%c%c%c", a, b, c);

In both of my examples the char array will be null terminated by the compiler so you can use it as a string, if you assign the characters one by one, make sure to place a null terminator at the end ('\0'), only then will you have a propper string.

Concatenate two characters in c

3 Answers3