transmission_auto_unrar.sh

#!/bin/bash

UNRAR_LOG="/config/unrar.log"
UNRAR_DESTINATION="$TR_TORRENT_DIR"

echo "unrar for $TR_TORRENT_NAME, in $UNRAR_DESTINATION"  >> $UNRAR_LOG

cd $UNRAR_DESTINATION;

if [ -n "$TR_TORRENT_NAME" ]; then

    if [ -f $TR_TORRENT_NAME ]; then

	unrar e "$TR_TORRENT_NAME" "$UNRAR_DESTINATION" >> $UNRAR_LOG;

    elif [ -d $TR_TORRENT_NAME ]; then

	echo "entering $TR_TORRENT_NAME" >> $UNRAR_LOG;
	UNRAR_DESTINATION="$UNRAR_DESTINATION/$TR_TORRENT_NAME"
	echo "new unrar destination $UNRAR_DESTINATION" >> $UNRAR_LOG
	cd "$TR_TORRENT_NAME";

	if [ -f *.rar ]; then
	    echo ".rar file found" >> $UNRAR_LOG;
	    files=(*.rar)
	elif [ -f *.part01.rar ]; then
	    echo ".part01.rar file found" >> $UNRAR_LOG;
	    files=(*.part01.rar)
	else
	    echo "!!!!!!!!!!!!!!!!!!!!!!!!!\ncouldn't match file pattern pls help\n!!!!!!!!!!!!!!!!!!!!!!!!!" >> $UNRAR_LOG;
	    exit 1
	fi

	for file in ${files[*]}; do
	    unrar e $file "$UNRAR_DESTINATION" >> $UNRAR_LOG;
	done
    else
	echo "!!!!!!!!!!!!!!!!!!!!!!!!!\nthis should be impossible. help?\n!!!!!!!!!!!!!!!!!!!!!!!!!" >> $UNRAR_LOG;
	exit 1
    fi

else
    echo "no name given" >> $UNRAR_LOG;
    exit 1
fi

In bash, quoting a wildcard makes it lose its special powers and becomes a literal. So, if [ -f *.rar ]; then is not the same as if [ -f "*.rar" ]; then.

Okay now we support multiple files and actually exit 1 when it fails