Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Compare the difference between two directories
Answer:
You have two directories, say /foo and /bar, and you want to compare the difference between this two directories, you can use
# diff -r /foo /bar
If you only want to know which files difference, you can use
# diff -qr /foo /bar
Factor numbers in Linux
Answer:
This command is very handy for finding the prime factors of number n.
E.g.
# factor 100
100: 2 2 5 5
Print large banner on printer
Answer:
This is a less well known command for Linux. It allow you to prints a large, high quality banner on the standard output.
Example:
# banner -w 80 Hello World
Where -w change the width of the output, in which the default is 132.
Test if local SMTP server is running
Answer:
To test if a local SMTP server is running, you can try to ping the port 25
# echo -e "quit" | nc localhost 25
220 ubuntu ESMTP Postfix (Ubuntu)
221 2.0.0 Bye
If no SMTP server is listening
# echo -e "quit" | nc localhost 25
localhost.localdomain [127.0.0.1] 25 (?) : Connection refused
Open two files side by side using vim
Answer:
If you have two files, you want to open both of them in vi/vim and edit side by side, you can do the following.
# vim -O foo.txt bar.txt
