Viewing Files

Several commands show a file's contents in different ways.

printf '%s\n' "line 1" "line 2" "line 3" "line 4" "line 5" "line 6" > log.txt

cat log.txt
echo "---"
head -n 2 log.txt
echo "---"
tail -n 2 log.txt
echo "---"
wc -l log.txt

line 1
line 2
line 3
line 4
line 5
line 6
---
line 1
line 2
---
line 5
line 6
---
6 log.txt

• cat prints the whole file (its name comes from "concatenate" — it can join several files).
• head -n N / tail -n N show the first or last N lines (10 by default).
• wc -l counts lines; wc -w words; wc -c bytes.
• (printf '%s\n' ... printed each argument on its own line to create a sample file — you'll meet printf again later.)

Long files: less

less log.txt opens a scrollable viewer: arrow keys or Space to scroll, /text to search, n for the next match, and q to quit.

Watching a growing file

tail -f app.log keeps showing new lines as they're added — the standard way to watch a log file live. Press Ctrl + C to stop.

Common mistakes

• Running cat on a huge file floods the terminal. Use less or head.
• Running cat on a binary file (like an image) prints garbage and can mess up the terminal; reset fixes it.