Viewing Files: cat, less, head, tail

A huge part of working on Linux is simply reading files: configuration files, logs, source code, CSV exports. You rarely need an editor just to look. This lesson covers the four classic viewers—cat, less, head and tail—plus wc for quick statistics, and shows when each tool is the right choice.

cat: Print the Whole File

cat (concatenate) dumps a file straight to the screen:

bash

cat /etc/hostname
cat notes.txt
cat -n script.sh        # -n adds line numbers
cat part1.txt part2.txt # print several files back to back

cat is perfect for short files. For a 10,000-line log it floods your terminal—that is what less is for. True to its name, cat can also concatenate files together, which becomes powerful once you learn redirection: cat part1.txt part2.txt > whole.txt.

less: Scroll Through Anything

less opens a file in a scrollable, searchable viewer without loading the whole file into memory, so it handles gigabyte logs effortlessly:

bash

less /var/log/syslog

Essential keys inside less:

Space / b – page down / page up
Arrow keys – scroll line by line
g / G – jump to the start / end of the file
/error – search forward for "error"; n for next match, N for previous
q – quit

If a command like git log or man ls drops you into a scrolling view, that is less—the same keys apply everywhere.

head: The First Lines

head shows the beginning of a file, ten lines by default:

bash

head /etc/passwd
head -n 3 data.csv      # just the first 3 lines
head -c 100 file.bin    # first 100 bytes

head -n 1 data.csv is the classic way to peek at a CSV header row before processing the file.

tail: The Last Lines

tail is the mirror image, showing the end of a file—which is where the newest entries of any log live:

bash

tail /var/log/syslog
tail -n 50 app.log        # last 50 lines
tail -f app.log           # follow: stream new lines as they arrive
tail -f app.log | grep -i error   # follow, but only show errors

tail -f (follow) is one of the most used commands in real operations work: start it, trigger your application, and watch log lines appear live. Press Ctrl+C to stop following.

wc: Count Lines, Words, Bytes

bash

wc -l access.log     # number of lines
wc -w essay.txt      # number of words
wc -c photo.jpg      # number of bytes

wc -l answers questions like "how many entries are in this log?" instantly.

Choosing the Right Tool

| Situation | Tool | |---|---| | Short config file | cat | | Long file, need to search or scroll | less | | Check a CSV header or file format | head | | Latest log entries | tail -n 50 | | Watch a log live | tail -f | | How big is this file? | wc -l or ls -lh |

Practice Session

bash

cat /etc/os-release
head -n 5 /etc/passwd
tail -n 5 /etc/passwd
wc -l /etc/passwd
less /etc/services      # practice /search, g, G, then q to quit

All of these files are safe, world-readable system files—perfect practice material on any Linux machine.

Key Takeaways

cat prints whole files; ideal for short ones and for concatenating.
less is a fast, searchable pager: / to search, q to quit.
head and tail show the start and end; -n controls how many lines.
tail -f streams a growing log in real time—indispensable for debugging.
wc -l counts lines for instant file statistics.

Next lesson: File Permissions and chmod — understand who can read, write and execute your files.