Piping and Redirection

Question

What is exact difference between piping and redirection?

Where should we use piping and where should we use redirection?

How they internall

Answer 1

Piping directs the output of a program to another program.

For example:

ls * | grep "name"

Pipes the names of all files in the current directory to grep. Re-direction directs or appends output to a file.

ls * > file  # writes all file names in current directory to the "file"
ls * >> file # appends all files names in current directory to the "file"

Piping saves you the hassle of having to write to a file, then read from a file to execute a program on the output of another program.

ls * > file
grep "name" file

is equivalent to

ls * | grep "name"

As for how it they work internally, I am only learning that my self now. But I found this link which offers some discussion on it.

How Does Piping Work in Linux?

You should use piping if you want to pass outputs between programs; use redirection if you want to write to a file.