shell script with options

http://www.mkssoftware.com/docs/man1/getopts.1.asp


EXAMPLE
This is an example of using getopts in a shell script. Compare it to the getopt example.

# Example illustrating use of getopts builtin. This
# shell script would implement the paste command,
# using getopts to process options, if the underlying
# functionality was embedded in hypothetical utilities
# hpaste and vpaste, which perform horizontal and
# vertical pasting respectively.
#
paste=vpaste # default is vertical pasting
seplist="\t" # default separator is tab

while getopts d:s o
do case "$o" in
d) seplist="$OPTARG";;
s) paste=hpaste;;
[?]) print >&2 "Usage: $0 [-s] [-d seplist] file ..."
exit 1;;
esac
done
shift $OPTIND-1

# perform actual paste command
$paste -d "$seplist" "$@"

How to make DHDall.xyz

#!/bin/bash

DHDfile=($(ls -1 DHD?????.xyz))  # Read all files of DHD?????.xyz
interval=$1        # Interval is the first argument.
: ${interval:=1}   # If there is no argument, default value is 1.


if [ -f DHDall.xyz ] # If DHDall.xyz exist
then
   rm DHDall.xyz     # then delete it.
fi
touch DHDall.xyz     # As DHDall.xyz is absent, touch it.

for (( i=0; i < ${#DHDfile[@]} ; i=i+$interval )) do
   cat  ${DHDfile[$i]} >> DHDall.xyz
done
exit

fortran file append

This partial code is to open existing (OLD) file, DHD00000.xyz, and write (APPEND) additional information from the end of the file

open(unit=1,file='DHD00000.xyz',status='old',position='append')
 write(1,*) "Here we go!"
close(1)

stop
end