how to merge two strings

Question

I have the following program which fails to merge the two strings because the string1 does not have enough space to hold the merged string .When string1 doesnt have enough space and without using the additional array to hold merged string how to return a merged string ?

 #include<stdio.h>
 #include<string.h>
 int main()
  { 
      void strcat2(char *str1,char *str2);
      strcat2("john","kris");
      getchar();
  }
  void strcat2(char *str1,char *str2)
   {
     for (; *str1++;);
     for (;*str1++ =*str2++;);

  }

This could be of use http://stackoverflow.com/questions/308695/c-string-concatenation — , Aug 22 '13 at 18:01
Is there any particular reason that you use `for` loops instead of `while`? And don't write into string literals, never. — Jens Gustedt, Aug 22 '13 at 18:52
I am confident that you had warnings as part of your compilation. Recommend that you show them when posting. — chux - Reinstate Monica, Aug 22 '13 at 20:00

Rahul Tripathi · Answer 1 · 2013-08-22T20:07:37.040

3

You can try this as this is a better one or just allocate more space.:-

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

char* concat(const char *s1, const char *s2)
{
    char *result = malloc(strlen(s1)+strlen(s2)+1);

    strcpy(result, s1);
    strcat(result, s2);
    return result;
}

edited Aug 22 '13 at 20:07

answered Aug 22 '13 at 18:07

Rahul Tripathi

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Suggest `concat(const char *s1, const char *s2)`. – chux - Reinstate Monica Aug 22 '13 at 20:06

score 2 · Answer 2 · answered Aug 22 '13 at 18:47

In C, you have to do your own memory allocation. That means that in general it is not possible for functions to return strings in the way garbage collected languages can. When you need to return a string from a function, you must either pass in the result string, pre-allocated by the caller, or else allocate it dynamically and rely on the caller to free it.

There's no shortcut in C, you just have to do the work.

how to merge two strings

2 Answers2