When preparing a system script file for FileMaker server you must place it in the proper folder with proper ownership and privileges.
Step 1: Copy file to proper location
cp example.sh /Volumes/OS_Drive_Name_Example/Library/FileMaker\ Server/Data/Scripts/example.sh
Step 2: Navigate to FileMaker Server scripts folder
cd /Volumes/OS_Drive_Name_Example/Library/FileMaker\ Server/Data/Scripts/
Step 3: Assign FileMaker server owner/group to the file:
sudo chown fmserver:fmsadmin example.sh
Step 4: Assign proper privileges:
sudo chmod 755 example.sh