# Junk Drawer

For all those little papers scattered across your desk

# I/O Funnels

23 Aug 2019 in Blog

I teach a lab, and think of a new way to teach I/O redirection operators.

## Problems to solve

We are software engineers, and we like to automate. We would prefer to automate:

• Keyboard input
• Output processing

Inputting entries for a program all day long is a boring job. So is copy-pasting the output into emails, as input for other programs, or as a test.

## Solutions

Files. It’s files all the way down.

### Input

We normally just type input while the program is running. We want to automate that. We use the < operator:

cmd <file


It sucks in the contents of file and funnels it as input to cmd

### Output

Output is normally sent to the console screen. We usually want to capture it and do something with it. We use the > operator:

cmd >file


It sucks the output of cmd and funnels it to file

You can combine them, too:

cmd <in >out
cmd >out <in
<in cmd >out
<in >out cmd


&c.