How to use pipe in Linux
Pipe | is very useful when you want to redirect the output of a program as an input of another program.
The combinations of using pipe in Linux is almost unlimited.
Some common usage:
1. count the number of lines in a file
cat test.txt | wc -l
2. read a very large text file
cat large.txt | less
3. filter filename from find util
find -type f | grep foo.txt