I have four array of strings. I would like to print out the strings with this formatting:

                        printf(" %d \t %s \t %s \t %s \t %s.\n",

It gives this output:

 17      func    sub     int     3.
 17      param   (null)          (null)          (null).
 17      alloc           4       (null)          xa.
 17      alloc           4       (null)          y.
 17      alloc           4       (null)          z.
 17      multiply        55      y       t0.
 17      divide          t0      z       t1.
 17      plus            xa      t1      t2.
 17      plus            t2      x       t3.
 17      func    main    void    0.
 17      alloc           4       (null)          a.
 17      alloc           4       (null)          b.
 17      alloc           4       (null)          c.
 17      arg             (null)          (null)          x.
 17      arg             (null)          (null)          y.
 17      arg             (null)          (null)          z.
 17      call            sub     3       t5.
 17      assign          t5      (null)          y.

How would I go about ignoring the nulls when printing? I am not sure how to do this.