Output to a File: >

So far, every command has printed its output to the screen. But what if you need to save that output? The > operator sends (redirects) a command's output into a file instead of displaying it.

The pattern is: COMMAND > FILE.

echo "Reactor online" > status.txt

Nothing appeared on screen: the text went into status.txt instead. You can verify with cat:

cat status.txt

Reactor online

Warning: > overwrites!

If the file already exists, > replaces its contents entirely. Think of it as "create or overwrite."

echo "Reactor offline" > status.txt
cat status.txt

Reactor offline

The old content is gone. When you need to keep existing content, you will use >> (next lesson).

Any command that produces output can be redirected: ls, grep, cat, date, anything.

Mission: Critical Alert Extraction

The sensor array has been logging readings to sensors.log, but the chief engineer wants the important lines split into their own files so the repair crew knows exactly what to fix.

1. Find the lines containing critical in sensors.log and save that output into a new file called alerts.txt instead of printing it to the screen.
2. Do the same for the healthy readings: capture the lines containing ok into a file called healthy.txt.
3. Create a folder called report and move both files into it.
4. Display report/alerts.txt to confirm the repair crew's list is correct.

Expected result

The report folder holds alerts.txt (the two critical lines) and healthy.txt (the three healthy readings).