Each command in the chain takes data, modifies it in some way, and passes it on to the next command. Programs are connected with 'pipes', and as a programmer of shell scripts you get to be the plumber. A pipe takes the output stream of one program and connects it to the input stream of another. For example, pipes make it easy to search many compressed files for lines containing a specific string. Variables Variables allow you to store information inside the Shell Environment.
All shell variables are of the same type and can hold numbers or text.
Using the data stored in a variable is done by perpending a dollar sign the variable name. The output of a shell command can also be stored in a variable.