How I exec sheel script from Postrgres Function ???

        Hi ALL!

               So  subj.   My     task   very simple and  i'm  not  a
 master c-programmer .
I write a shell scripts but , how  attach  it  to Postgres i can't found
in  docs  or FAQ.
 Now  i write  simple-and-stupid C-function  for exec my script but its
not a god solution! :(
 Thanks in advance.
       Vic Konovalov.