cat a b | sort | uniq > c # c 是a和b的合集
cat a b | sort | uniq -d > c # c 是a和b的交集
cat a b b | sort | uniq -u > c # c 是a和b的不同

awk ‘{ x += $3 } END { print x }' myfile

find . -type f -ls

find . -name /*.py | xargs grep some_function
cat hosts | xargs -I{} ssh root@{} hostname

cat access.log | egrep -o ‘acct_id=[0-9]+' | cut -d= -f2 | sort | uniq -c | sort -rn ]