Unistd.h is not present in common libs

I would like to use the below API to get the absolute path of working directory , so  i can use them in the code for file operations , i came to know unistd.h file is not present , then how can i get the absolut path without statically defining them

   if (getcwd(cwd, sizeof(cwd)) != NULL) {
       printf("Current working dir: %s\n", cwd);