Problem printing characters and creating a new string array

Question

I have created a program that loads an expression from an input file and converts the expression from infix to postfix form.

So in the file I have expressions. Each expression is placed on a separate line in the text file. I read from the file line by line and form a array of strings that make up the expressions from the text file. I take each string from the array and convert it to postfix form.

The problem is that when converting from infix to postfix, I print out the characters. The array of strings from the input is not changed.

Here' s code:

for(i = 0; i < strlen(c); i++)
    {
        if(c[i] == '(')
            stek.arr[++stek.tos] = '(';

        else if(c[i] == ')')
        {
            while(stek.arr[stek.tos] != '(')
            {
                printf("%c", stek.arr[stek.tos--]);
              
            }

            stek.tos--; 
        }
        // if Operator
        else if(isOperator(c[i]))
        {
            while(stek.tos != -1 && !isHigherPrecedence(c[i], stek.arr[stek.tos]))
            {
                printf("%c", stek.arr[stek.tos--]);
               
            }

            stek.arr[++stek.tos] = c[i];
        }
        // if operand
        else
        {
            printf("%c", c[i]);
        }

    }
    while(stek.tos != -1)
    {
        printf("%c", stek.arr[stek.tos--]);
       
    }

This is just the conversion code from infix to postfix form.

c-represents a string of expressions loaded from a file, it is at the beginning a string of the first line, a string of the second line, etc.

My question is : When a string is converted from infix to postfix form, it is printed character by character. How to create a new array of strings that will contain only the postfix form?

I want these characters that are printed individually in this code to be put into an array, and it becomes an array of strings.