sugree@sugree-laptop:~$ history|awk '{a[$2]++} END{for(i in a){printf "%5d\t%s\n",a[i],i}}'|sort -rn|head
   78   ls
   72   git
   57   ant
   55   vi
   50   cd
   25   du
   21   wget
   12   ssh
   12   dpkg
   11   rm