The Start and End of a File: head and tail

head: the first lines

head prints the first 10 lines of a file. -n chooses how many:

head numbers.txt
head -n 3 numbers.txt

In the terminal

student@vulntech:~$ head numbers.txt
Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10
student@vulntech:~$ head -n 3 numbers.txt
Line 1
Line 2
Line 3

tail: the last lines

tail prints the last 10 lines. It's perfect for logs, where the newest entries are at the end:

tail -n 3 numbers.txt
tail -n 2 logs/web.log

In the terminal

student@vulntech:~$ tail -n 3 numbers.txt
Line 198
Line 199
Line 200
student@vulntech:~$ tail -n 2 logs/web.log
2024-06-01 10:59:00 INFO request 119 served
2024-06-01 11:00:00 INFO request 120 served

Following a log with tail -f

tail -f (follow) keeps the file open and prints new lines as they're added. System administrators use it to watch a log while something is happening. Press Ctrl+C to stop:

tail -f /var/log/messages

Starting from a line

tail -n +195 means from line 195 to the end:

tail -n +195 numbers.txt

In the terminal

student@vulntech:~$ tail -n +195 numbers.txt
Line 195
Line 196
Line 197
Line 198
Line 199
Line 200

Remember: head = beginning, tail = end, -n = how many lines, tail -f = keep watching.