Performing grep operation in tar files without extracting

the tar command has a -O switch to extract your files to standard output. So you can pipe those output to grep/awk

tar xvf  test.tar -O | awk '/pattern/{print}'

tar xvf  test.tar -O | grep "pattern"

eg to return file name one pattern found

tar tf myarchive.tar | while read -r FILE
do
    if tar xf test.tar $FILE  -O | grep "pattern" ;then
        echo "found pattern in : $FILE"
    fi
done

The command zgrep should do exactly what you want, directly.

for example

zgrep "mypattern" *.gz

http://linux.about.com/library/cmd/blcmdl1_zgrep.htm