1.<

python read-input.py < nums-0-999 

2.> >>

ls /home/jackiechen/ >home.txt
ls /home/jackiechen/ >>home.txt
cat < foo > foo //Attention 
cat < foo >> foo //Attention 

3.head tail

head -n 3 table //head -n -2 table 
tail -n 3 table
head -n 3 table|tail -n 2

4.tr

tr -s "\n" <bad-new-line >good-new-line

5.sort

cat pumpkinsizes |tail -n +3|sort -n -t '|' -k2 -r|head -n 3
cat pumpkinsizes |tail -n +3|sort -n -t '|' -k2|head -n 2

6.uniq

cat words|tr [:space:] "\n"|tr [:punct:] "\n"|tr -s "\n"|sort |uniq >words-sorted 
cat words|tr [:space:] "\n"|tr [:punct:] "\n"|tr -s "\n"|sort |uniq -cd |sort -n -k1 > words-count 

7.cut

 wc -w words|cut -d " " -f 1

8.join

join <( cat pumpkinsizes|tail -n +2|sort) <( cat emails |sort)
join <( cat pumpkinsizes|tail -n +2|sort) <( cat emails |sort)|tr -d "|" |sort -k2 -nr|head -n1|cut -d " " -f 3
grep "[0-9]$" pumpkinsizes |sort -k2 -t '|' -n|tail -n 1 >winer |join emails winer|cut -d " " -f 2

9.sed
10.awk
11.tee
12.comm
13.grep