SHELL

script inside script bash

#!/bin/bash
cat > sim.in << WWW

 20 ns production run (explicit solvent)  
  &cntrl   
   imin=0,   
   ntx=5,
   irest=1,   
   ntpr=10000,
   ig=-1,   
   ntp=1,
   taup=2.0, 
   pres0=1, 
   ioutfm=1,
  /

WWW

this will right sim.in file