1. head1.txt
2. head2.txt 
3. head3.txt
4. head4.txt

1. Optimization with ZMAT
2. Optimation with Cartesian
3. Frequency
4. Transition State Search

#!/bin/bash

# Script to add input headers to GAMESS(US) input files generated by ChemCraft.
# This script assumes that there are 4 headers that you can use:
# opt.zmat.txt, opt_cart.txt, freq.txt and TS_Search.txt
# These files should be placed in /home/$USER directory and modified to your liking.

echo " Please chose the header you want to add:
1. Optimization with ZMAT
2. Optimation with Cartesian
3. Frequency
4. Transition State Search"
read choice
            if [ "$choice" = "1" ]; then
               head='opt_zmat'
            
            elif [ "$choice" = "2" ]; then
               head='opt_cart'
            fi

            if [ "$choice" = "3" ]; then
               head='freq'
            fi

            if [ "$choice" = "4" ]; then
               head='TS_Search'
            fi
sed -i '1,2d' $in.inp
cat /home/$USER/$head.txt $in.inp >tmp && mv tmp $in.inp