C snippets

2Darray.c

// create
char** arr = (char**) malloc(10 * sizeof(char**));

for(int i = 0; i < 10; ++i) {
  *(arr + i) = (char*) malloc(sizeof(char*) * 4);
  strcpy(*(arr + i), "test");
}

// use
for(int i = 0; i < 10; ++i) {
  printf("%s\n", *(arr + i));
}

// free
for(int i = 0; i < 10; ++i) {
  free(*(arr + i));
}

free(arr);

concat.c

#include <string.h>

char* concat(char* a, char* b) {
  // + 1 for '\0'
  char* s = (char*) malloc(sizeof(a) + sizeof(b) + 1);

  if(s == NULL) {
    // malloc error
  }

  // strcat needs '\0' to copy after.
  // s being uninitialized, we can either set it by hand at [0] or use strcpy.
  //
  // s[0] = '\0';
  // strcat(s, a);
  // strcat(s, b);
  //
  // strcpy(s, a);
  // strcat(s, b);
  *s = '\0';
  strcat(s, a);
  strcat(s, b);

  return s;
}