concatenating two strings

This is a discussion on concatenating two strings within the C Programming forums, part of the General Programming Boards category; Hi, I am new to c. I was trying to print out this message using pointers. This is a test ...

  1. #1
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    concatenating two strings

    Hi,
    I am new to c. I was trying to print out this message using pointers.

    This is a test
    No - it is not a test

    This is my code.

    Code:
    #include<stdio.h>
    #include<string.h>
    #include<stdlib.h>
    
    int main(){
       char *p = "This is a test";
       printf("%s\n",p);
       strcat(p,"No - this is a test");
       printf("%s\n",p);
    }
    Your help will be appreciated.

  2. #2
    Obsessed with C chrismiceli's Avatar
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    not sure, but I think when you use char *p = "hi"; that you make a constant, you can't alter it because the compiler allocated space only for those character, I think...

  3. #3
    ATH0 quzah's Avatar
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    Originally posted by chrismiceli
    not sure, but I think when you use char *p = "hi"; that you make a constant, you can't alter it because the compiler allocated space only for those character, I think...
    Correct. They're using string literals, and as such, you cannot (read: shouldn't try to) modify them.

    You'll probably want an array for the first sentence, long enough to hold them both. Either that or do it dynamicly. But an array should suffice for this.

    However, if your code actually did work, you would end up with this output:
    This is a test
    This is a testNo - this is a test
    strcat adds one string to the end of another. It doesn't replace the first string with the second.

    If you really want the first string overwritten, you'd need to use strcpy (or strncpy) or something similar.

    Quzah.
    Hope is the first step on the road to disappointment.

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