在作为参数传递给函数时串联字符串

Question

There is a function that takes string as a parameter/argument.

Func(char* strA)
{
...
}

I have two strings;

#define FIRST "first"
char efg[] = " second";

I want to basically send "first second" as argument to Func(strA) , but I do not want to use strcat(FIRST, efg); as it would permanently change my macro FIRST .

Is there a way to send "first second" as argument without upsetting the macro above?

Answer 1

You can use of sprintf function to write first in a temp buffer:

#define FIRST "first"
char efg[] = " second";  
char* space = " ";
char* strA = calloc(strlen(FIRST) + strlen(space) + strlen(efg) + 1, sizeof(char));  

sprintf(strA,"%s%s%s",FIRST, space, efg);

Func(strA);  

free(strA);  

Give it a Try!!

---

Note: don't forget free() dynamic allocated memory.

Description:
The sprintf() function is just like printf() , except that the output is sent to buffer. The return value is the number of characters written.

Answer 2

If it's permissable to you not to have efg as a variable but as a string literal, then because adjacent string literals are implicitly concatenated (spec C99: 5.1.1.2.6) you could simply have the following:

Func(FIRST " second");

And for the same reason you could alternatively declare efg as

char efg[] = FIRST " second";

Either way, much easier than strcat or sprintf.

Answer 3

也许您可以先使用strcpy()将宏复制到新的char数组，然后使用strcat( new_var, efg ) -将其作为参数传递。