Pipes — joining commands

The big idea: pipes

This is what makes the shell powerful. A pipe | sends one command's output straight into the next command:

cat fruits.txt | sort

cat produces the lines; sort receives them and puts them in order. No file in between.

Build a chain

You can join as many as you like, like an assembly line:

cat fruits.txt | sort | uniq

sort orders the lines, then uniq removes neighbouring duplicates — so you get each fruit once.

Small tools, big results

Each command does one job well. Pipes let you combine them to answer real questions:

cat fruits.txt | sort | uniq | wc -l

"How many different fruits are there?" — sort, dedupe, then count. That is the Unix way.

Send the output of cat fruits.txt into wc -l with a pipe |, to count the lines.

# cat the file, piped into wc -l

Click Run to see the output here.

List each fruit once, in order. Pipe sort into uniq: cat fruits.txt | sort | uniq.

# cat | sort | uniq

Click Run to see the output here.

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