Background
 I recently came into contact with the Linux system. In the process of learning, there is a command alias that I feel particularly interesting. So I wrote my own command alias zzm='echo "wlz, I love u"' according to the tutorial, and then immediately showed it to my girlfriend. She first looked at those lines of code attentively, and then understood After that, we smiled shyly, with our eyes facing each other, we were all very excited.
 
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 But when I continued to learn Linux the next day, I first typed zzm on the command line, but found that I didn’t have this command anymore. It turned out that love would disappear, right? .
 
 No, how could I let love disappear so unclearly! I'm not convinced!
 
 So, I started to look up information and think about how to make the custom alias command permanent. There are some methods on the Internet, but there are some differences between different Linux distributions, and some methods are not applicable. My virtual machine is Ubuntu 18.04TLS.
 
 I wanted to read a few chapters of the Linux book today, but I spent a long time studying this. But I don't regret at all for spending the time to delve into a small problem. Because this is the guardian of love, and at the same time, learning/research is actually a process of discovering various small problems and then self-exploring.
 
 Not much nonsense, let me talk about how I solved it on Ubuntu 18.04TLS.
 
 
Solution
 First adjust the current working directory to /home/own user/
 
cd /home/zzmine
 Then, search for the .bashrc file (because it is a file starting with ., you need to use the -a option to display)
 
ls -a -l | grep .bashrc
 
 After confirming that there is this file, open it!
 
less .bashrc
 
 Scroll down and you will see a sentence
 
 You may want to put all your additions into a separate file like
 ~/.bash_aliases, instead of adding them here directly.
 
 This means that you can define a separate file .bash_aliases to store your own defined commands instead of adding them directly to the .bashrc file. Then let's write a .bash_aliases file in the current working directory /home/zzmine.
 
vim .bash_aliases
alias zzm='echo "wlz,I love u"'
 
 Then save, exit, and finally re-execute the .bashrc file to make it effective
 
source .bashrc
 
 Then, restart, directly enter the previously defined command, and find that it is all right!
 
 
Extension
 In fact, the usefulness of custom commands is much more than simply showing affection. You can combine multiple commands and assign aliases to simplify future work. For example, you can set the first push to github command as:
 
alias gpush ='git add .; git commit -m "first commit"; git push -u origin master'
 Finally, if readers have questions or other ideas about the article, welcome to share!