Explain about Pipes in UNIX?

Answer 1

To see who is on the system with you, type

% who

One method to get a sorted list of names is to type,

% who > names.txt
% sort < names.txt

This is a bit slow and you have to remember to remove the temporary file called names when you have finished. What you really want to do is connect the output of the who command directly to the input of the sort command. This is exactly what pipes do. The symbol for a pipe is the vertical bar |

For example, typing

% who | sort

will give the same result as above, but quicker and cleaner.

To find out how many users are logged on, type

% who | wc -l
Exercise 3b

a2ps -Phockney textfile is the command to print a postscript file to the printer hockney.

Using pipes, print all lines of list1 and list2 containing the letter 'p', sort the result, and print to the printer hockney.