Input from a File: <

Output redirection (>, >>) controls where output goes. Input redirection (<) controls where input comes from.

The pattern is: COMMAND < FILE.

Some commands read from standard input (stdin), the keyboard by default. With < you can feed them a file instead:

wc -l < manifest.txt

5

Here wc -l counts lines. Instead of typing lines on the keyboard, it reads them from manifest.txt. Note that the filename is not shown in the output. That is the subtle difference from wc -l manifest.txt (which prints the name alongside the count).

When is < useful?

Many commands accept filenames as arguments directly, so < is not always required. It becomes valuable when:

• A program only reads stdin (no filename argument).
• You want to hide the filename from the output.
• You are combining < with > in one command: sort < unsorted.txt > sorted.txt.

Mission: Crew Headcount

Life support needs an exact headcount to calibrate oxygen levels. The manifest is stored in crew.txt, one name per line.

1. Count the crew from crew.txt using input redirection, so only the number appears, no filename beside it.
2. Save that clean count into a new file called headcount.txt, combining input and output redirection in a single command.
3. Create a folder called life-support and move headcount.txt into it.
4. Display the stored file to confirm it holds only the number.

Expected result

life-support/headcount.txt contains just the number 6.