omes@lucas:~$ perl -e 'print "fictive    fictive"x10'> temp.fic
omes@lucas:~$ cat temp.fic 
fictive    fictivefictive    fictivefictive    fictivefictive    fictivefictive 
   fictivefictive    fictivefictive    fictivefictive    fictivefictive    ficti
vefictive    fictive
omes@lucas:~$ sed s/fictive/\0/g temp.fic 
0    00    00    00    00    00    00    00    00    00    0