mjhjmtu

I am struggling to use IF statements.

A directory is passed to the script and that directory (which contains any number of subfolders) will either have .txt files in or .tmp files in and my ultimate goal is to copy all the .tmp files to one folder and and .txt files to another.

Currently have:

shopt -s nullglob
if [[ -n $(echo *.txt) ]]; then

elif [[ -n $(echo *.tmp) ]]; then

else
 echo "nothing Found"
fi

But it doesn't check the sub directories. Is there something missing?

You'll want to use the find command:

find "$start_dir" -type f -name '*.txt' -exec cp -t "$txt_destination" '' +
find "$start_dir" -type f -name '*.tmp' -exec cp -t "$tmp_destination" '' +

But it doesn't check the sub directories. Is there something missing?

Well, a normal glob doesn't recurse to subdirectories. Since you're using shopt, you're probably using Bash, which supports the **/ notation for recursive globs, provided you set shopt -s globstar. With it set, **/*.txt would expand to the all files matching *.txt also in subdirectories of the current directory.

ikkachu explained bash can do recursive globbing, but didn't say how. So, let's show how:

shopt -s globstar extglob nullglob
txt_files=(**/!(*test*|*sample*).txt)
if (( $#txt_files )); then
 cp -t "$txt_files[@]" $txt_destination
fi

tmp_files=(**/!(*test*|*sample*).tmp)
if (( $#tmp_files )); then
 cp -t "$tmp_files[@]" $tmp_destination
fi

zsh has been able to do this for over a decade, if I remember correctly. If you're using zsh rather than bash:

setopt extendedglob
txt_files=( **/*.txt~*(test|sample)*(N.) )
if (( $#txt_files )) cp -t $txt_files $txt_destination

tmp_files=( **/*.tmp~*(test|sample)*(N.) )
if (( $#tmp_files )) cp -t $tmp_files $tmp_destination

Or in a more C style:

setopt extendedglob nullglob
txt_files=( **/*.txt~*(test|sample)*(.) )
if [[ $#txt_files != 0 ]] 
 cp -t $txt_files $txt_destination


tmp_files=( **/*.tmp~*(test|sample)*(.) )
if [[ $#tmp_files != 0 ]] 
 cp -t $tmp_files $tmp_destination

I didn't forget any quotes there; zsh keeps track of array element boundaries rather than just breaking on spaces. The semicolons after [[ ]] tests are also optional.