Mac/Unix SHELL script help

Hello,

I would really appreciate it if a seasoned Unix Shell script user could look over my code and explain how I can fix it to make it work. I got this script from a coworker and I don't know how to use it.

Here is the script:

#!/bin/sh
filename="$1"
output="${filename%.*}_modified.csv"
cd $(dirname $filename)
string1="Reading #2 from /home/njhunsak/images/"
string2="/antsCorticalThickness/BrainSegmentation.nii.gz"
grep -vwE "(Reading #1|LabelID|^(    0))" ${filename} | sed -e "s|$string1||" -e "s|$string2||" -e "s|/|,|" -Ee "s/[ ]+/,/g" > temp.txt
awk '/^[0-9][0-9][0-9],/{for(i=0;i<6;i++)print}' temp.txt > part1.txt
awk '/^,/{print}' temp.txt > part2.txt
sed -i '' -e "s|,1,|,csf,|" -e "s|,2,|,gm,|" -e "s|,3,|,wm,|" -e "s|,4,|,subcortical,|" -e "s|,5,|,brainstem,|" -e "s|,6,|,cerebellum,|" part2.txt
paste part1.txt part2.txt > ${output}
perl -pi -e 'print "cabilid, subjectid, label, mean, std, max, min, count, volume (mm^3), extent x, extent y, extent z\n" if($.==1)' ${output}
rm part1.txt
rm part2.txt
rm temp.txt

What I have tried to do is open terminal and type "sh ~/Desktop/script.sh" but after I press enter to send the command, the next line says "usage: dirname path" and I don't know how to proceed.

I tried typing in the directory path that my data.txt is in, but pressing enter after typing that doesn't do anything.

I am glad I can actually run the script but it seems I don't know what to do once I am in the script.

Was I supposed to change some text in the script or is this script interactive and asking me to press a special button to proceed?

Thanks in advance for helping this newbie!