~ $ mkdir tmp ~ $ cd tmp ~/tmp $ mkdir a ~/tmp $ cd a ~/tmp/a $ mkdir b ~/tmp/a $ cd b ~/tmp/a/b/ $ mkdir c ~/tmp/a/b/ $ cd c ~/tmp/a/b/c $ 

mkdir -p tmp/a/b/c 

cp a.tar.gz /tmp cd /tmp tar xzvf a.tar.gz 

tar xzvf -C /tmp a.tar.gz 

cat a.txt | grep "a" 

grep "a" a.txt 

cat a.txt | grep "a" | wc -l 

grep -c "a" a.txt 

~/tmp $ ls -l /tmp| grep Dec -rw-r--r-- 7 joe joe 12043 Jan 27 20:36 December_Report.pdf -rw-r--r-- 1 root root 238 Dec 03 08:19 README -rw-r--r-- 3 joe joe  5096 Dec 14 14:26 archive.tar ~/tmp $ 

~/tmp $ ls -l | awk '$6 == "Dec"' -rw-r--r-- 3 joe joe  5096 Dec 14 14:26 archive.tar -rw-r--r-- 1 root root 238 Dec 03 08:19 README ~/tmp $