# Select two most recent files with corresponding file name format and 
# copy to destination directory
 
for file in 'ls -1t OUS_*_*_*.txt | head -n 2'
do 
    cp "$file" $testDestDir
done

cp: cannot access ls -1t OUS_*_*_*.txt | head -n 2: No such file or directory

cp: cannot access ls: No such file or directory
cp: cannot access -1t: No such file or directory
cp: cannot access |: No such file or directory
cp: cannot access head: No such file or directory
cp: cannot access -n: No such file or directory
cp: cannot access 2: No such file or directory