Programming :: Tar *.gz/.bz2 Extraction - Deploy With Bash Script

I thought of a command that would make my life easier, though I do not know how to deploy it with bash script. The idea- A simple script that would check in a the current directory for *.bz2 or *.gz files,and when finds one of those,or both - execute a tar -xvf *.bz2/*.gz following the files that have been found there. It should be very simple,as I am very new to bash,I can`t figure that out. I wrote :

[Code]....

The idea ls command that would find *.gz files in the current dir,then it outputs the errors to ./tmp.txt, if there were no errors = a tar.gz archive found,tmp.txt will be blank,hence the cat command that checks the file. The wrong - I couldn`t succeed with the "cat 'tmp.txt' == '' ;" ,as cat command searches == as a file and it fails.