Here is an iovec version, doing it all in a single writev.

  #include <unistd.h>
  #include <stdlib.h>
  #include <string.h>
  #include <alloca.h>
  #include <sys/uio.h>

  int main(int argc, char **argv)
  {
    if (argc > 1) {
      int nstr = argc - 1;
      char **svec = argv + 1;
      int i, j;
      struct iovec *iov = alloca(sizeof *iov * nstr * 2);
      for (i = 0, j = 0; i < nstr; i++, j += 2)
      {
        iov[j].iov_base = svec[i];
        iov[j].iov_len = strlen(svec[i]);
        iov[j + 1].iov_base = " ";
        iov[j + 1].iov_len = 1;
      }
      iov[j - 1].iov_base = "\n";
      writev(STDOUT_FILENO, iov, j);
    }

    return 0;
  }

#include <numerous_caveats.h>. We are not checking that everything got written, let alone handling a partial write. Systems have some limit on how many elements you can have in the iov array passed to writev.