strcat to concatenate a and b without actually changing a or b

Question

I know I can have a statement as such

    strcat( a, b );
    int alen = strlen( a );
    printf("a and b concatenated = %s and its length is %d\n", a, alen );

However, I want to preserve a, so I am trying use something more like this:

    strcat( a, b );
    int xlen = strlen( x );
    printf("a and b concatenated = %s and its length is %d\n", x, xlen );

How do I fix the first line with strcat so that it concatenates a and b into x?

Am_I_Helpful · Accepted Answer · 2015-04-05T19:57:23.933

5

You should use the following :-

strcpy(x,a);
strcat(x,b);
int xlen = strlen(x);
printf("a and b concatenated = %s and its length is %d\n", x, xlen );

Voila,and that's it.

edited Apr 05 '15 at 19:57

answered Apr 05 '15 at 19:55

Am_I_Helpful

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Thank you, that is simple enough. – tinkerton101 Apr 05 '15 at 19:56
1

there is an important detail to always check. Specifically, is the length of 'x' large enough to hold strlen(a) + strlen(b) +1 – user3629249 Apr 06 '15 at 22:10

score 0 · Answer 2 · answered Apr 06 '15 at 20:07

0

I found that the following as works as well:

    /* Concatenate a and b */
    char x[SIZE1+SIZE2] = “”;
    strcat(x , a );
    strcat(x , b );

    printf("a and b concatenated = %s and its length is %d\n", x, (int)strlen(x) );

answered Apr 06 '15 at 20:07

tinkerton101

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if SIZE1 and SIZE2 are related to strlen(a) and strlen(b) then the result is not large enough, because strlen() is the offset to the trailing NUL byte so need to add +1 to get the proper length. Also, the first line causes x[0] to contain '\0'. it does not clear all of x[]. suggest using: ;char x[SIZE1+SIXE2+1] = {'\0'}; to clear the whole array and to not generate a literal (containing only a '\0' character) in readonly memory – user3629249 Apr 06 '15 at 22:15

strcat to concatenate a and b without actually changing a or b

2 Answers2