Concatenating strings in C, which method is more efficient?
c, concatenation, performance, string
Solution
For readability, I'd go with
char * s = malloc(snprintf(NULL, 0, "%s %s", first, second) + 1);
sprintf(s, "%s %s", first, second);
If your platform supports GNU extensions, you could also use `asprintf()`:
char * s = NULL;
asprintf(&s, "%s %s", first, second);
If you're stuck with the MS C Runtime, you have to use `_scprintf()` to determine the length of the resulting string:
char * s = malloc(_scprintf("%s %s", first, second) + 1);
sprintf(s, "%s %s", first, second);
The following will most likely be the fastest solution:
size_t len1 = strlen(first);
size_t len2 = strlen(second);
char * s = malloc(len1 + len2 + 2);
memcpy(s, first, len1);
s[len1] = ' ';
memcpy(s + len1 + 1, second, len2 + 1); // includes terminating null
Problem
I came across these two methods to concatenate strings: Common part: ``` char* first= "First"; char* second = "Second"; char* both = malloc(strlen(first) + strlen(second) + 2); ``` Method 1: ``` strcpy(both, first); strcat(both, " "); // or space could have been part of one of the strings strcat(both, second); ``` Method 2: ``` sprintf(both, "%s %s", first, second); ``` In both cases the content of `both` would be `"First Second"`. I would like to know which one is more efficient (I have to perform several concatenation operations), or if you know a better way to do it.