script to create depth files from envelope files

#! /bin/bash
if [ "$#" != "2" ]; then
   if [ "$#" != "3" ]; then
        echo "*****    env2depth ERROR    *****"
        echo "Usage:   env2depth  input-pathname output-pathname [END-DEPTH]"
        exit
   fi
fi
if [ "$1" == "$2" ]; then
        echo "*****     env2depth ERROR    *****"
        echo "Do not use the same directory for output as input (it causes a loop)."
        exit
fi
declare OSI edepth
let OSI=1 edepth=16000
dir_in="$1"
dir_out="$2"

LINE=" "
if [ "$#" == "3" ]; then
   LINE="     sdepth 0  edepth $3"
   edepth=$3
fi

if [ $edepth -lt 8192 ]; then
        OSI=.5
fi
if [ $edepth -lt 4096 ]; then
        OSI=.25
fi
if [ $edepth -lt 2048 ]; then
        OSI=.125
fi

cd "$dir_in"
for x in *sgy ; do
        extension=${x##*.}
        if [ $extension = sgy ]; then
                echo "reading file: $dir_in/$x"
                echo "writing file: $dir_out/depth-$x"
                cd "-"
sioseis << eof
procs diskin filter wbt avenor mix gains2 t2d header3 diskoa end
diskin
        ipath $dir_in/$x end
end
prout
   fno 0 lno 999999 noinc 1000 end    ! print every 500th trace
end
filter
    ftype 0 pass 2 500 dbdrop 48 end
end
t2d
   $LINE
   osi $OSI  vtp 1500 0 end
end
gains2
    subwb yes type 5 alpha 5 end
end
avenor
   sets 0 .1 addwb yes end
end
wbt
   vel 1500 end
end
mix
   weight 1  1 end
end
header3
   c30 'SIOSEIS processing step 1:  convert correlates to envelope.'
   c31 'step 2: procs diskin filter wbt avenor mix gains2 t2d header3 diskoa'
   c32 '        filter ftype 0 pass 2 500 dbdrop 48 end'
   c33 '        wbt vel 1500 end # convert water depth to time'
   c34 '        avenor sets 0 .1 addwb yes end'
   c35 '        mix weight 1  1 end'
   c36 '        gains2 subwb yes type 5 alpha 5 end # exponential gain from wb'
   c37 'Notes: '
   c38 '1)  The data sample interval is $OSI kilometers, thus other seismic'
   c39 '    packages should treat it like time.'
   c40 '2)  The deep water delay has been removed - all data start at zero.'

   end
end
diskoa
    opath $dir_out/depth-$x end
end
end
eof
chmod 444 $dir_out/depth-$x
cd "-"

      fi
done