6 shell tips to make scripts look less amateurish (1 minute Series)

open_idh31hqp 2020-11-11 09:29:14
shell tips make scripts look


Long article 《memcache Core technology points 》 Reading is low , restart 1 Minute Series , The fast disappearing age , Fragmentary time, maybe you like the essay better , I prefer technical practice articles .
Voice over : Tell the truth , Technical thinking article (WHY, HOW), It's better than technology practice (WHAT) It's harder to write .

How to make your own shell Not so Amateur ? below 6 A little practice will help .
Voice over : This article originates from Google A practice of , Part of it is extracted 1 What you can read in minutes , Added some analysis .

One 、 Start with the following sentence

6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
set -o nounset
By default , Encountered a variable that doesn't exist , Will ignore and continue to execute , And that's often not what you expect , Add this option , It can prevent the consequences from spreading , Terminate execution of script .
Voice over : Some mistakes in variable names , It's going to take a long time to debug , In this way , This kind of hand Miss second detection .


set -o errexit
By default , Encountered execution error , Will skip and continue to execute , And that's often not what you expect , Add this option , It can prevent the consequences from spreading , Terminate execution of script .
Voice over : There are some Linux command , for example rm Of -f Parameters can force errors to be ignored , At this point, the script cannot capture errexit, Such parameters are not recommended in scripts .

These two options , All conform to fail fast Design concept .

Two 、 It is necessary to encapsulate functions

Don't patronize and write down , Encapsulation can improve reuse .
6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
As in the above example :
log()
Simple packaging , Can save a lot of
[$(date +%Y/%m/%d\ %H:%M:%S)]
Duplicate code for .
Voice over : This log() I little interesting , Have you learned ?






meanwhile , Encapsulation can also improve the readability of the code .
6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
As in the above example :
ExtractBashComments
Than
egrep "^#"
It's much more readable .
Voice over : Some friends will say , I don't know English .






3、 ... and 、 Use readonly and local Modifying variables

6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
readonly
seeing the name of a thing one thinks of its function , read-only .

local
Variables within a function .

Don't try to save time , While improving security , Can avoid a lot of people to collapse of the inexplicable mistakes . Is the script written professionally , It's not a high point , It is absolutely necessary to embody from the basic skills .
Voice over : It is said that , One C++ What level of programmers , from ta In the code const How often do you use it , Can see .

Four 、 Use $() Instead of `( Back single quotes )

6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
Why? ? Look at the example above and you will understand :
(1)$() Can support embedded ;
(2)$() No need to escape ;
(3) Some Fonts ,`( Back single quotes ) and ’( Single quotation marks ) It's like , It's easy to confuse people ;



5、 ... and 、 Use [[]] Instead of []

Use single brackets :
6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
Use double brackets :
6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )


See the difference ?[[]] More in line with the human code :
(1) Avoid escape problems ;
(2) There are many new features ;

New features include, but are not limited to :
|| : Logic or
&& : Logic and
< : String comparison ( There is no need to escape )
== : wildcard (globbing) String comparison
=~ : Regular expressions (regular expression, RegEx) String comparison
6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
It should be noted that , from bash3.2 Start , Neither wildcards nor regular expressions can be enclosed in quotation marks ( therefore , The above example , Quotation marks are literal comparisons ).
6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
So if there's a space in the expression , It has to be stored in a variable , Then compare the wildcard with the regular .








6、 ... and 、echo It's not the only way to debug

6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
It can be used -n Check the syntax of the script .
6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )

It can be used -v Tracking the execution of each command in the script .
6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )

It can be used -x Tracking the execution of each command in the script , And add expanded information .

Of course , It can also be in scripts , add to
set -o verbose
set -o xtrace
To permanently specify the output debug information .
Voice over : Try more on the machine and you'll see .



I hope this 1 Minutes, we have a harvest .
6 strip shell Tips , Make scripts look less amateurish (1 Minute Series )
Architect's way - Share technical ideas
Related to recommend :
《 Write a cache, What technical points should be mastered 》



research , When writing a script :
(1) It's because of a mistake , Have you ever driven yourself crazy ?
(2) It's because of the escape , Have you ever made yourself dizzy ?
(3) Yes, it is echo Debugging ?


版权声明
本文为[open_idh31hqp]所创,转载请带上原文链接,感谢

  1. [front end -- JavaScript] knowledge point (IV) -- memory leakage in the project (I)
  2. This mechanism in JS
  3. Vue 3.0 source code learning 1 --- rendering process of components
  4. Learning the realization of canvas and simple drawing
  5. gin里获取http请求过来的参数
  6. vue3的新特性
  7. Get the parameters from HTTP request in gin
  8. New features of vue3
  9. vue-cli 引入腾讯地图(最新 api,rocketmq原理面试
  10. Vue 学习笔记(3,免费Java高级工程师学习资源
  11. Vue 学习笔记(2,Java编程视频教程
  12. Vue cli introduces Tencent maps (the latest API, rocketmq)
  13. Vue learning notes (3, free Java senior engineer learning resources)
  14. Vue learning notes (2, Java programming video tutorial)
  15. 【Vue】—props属性
  16. 【Vue】—创建组件
  17. [Vue] - props attribute
  18. [Vue] - create component
  19. 浅谈vue响应式原理及发布订阅模式和观察者模式
  20. On Vue responsive principle, publish subscribe mode and observer mode
  21. 浅谈vue响应式原理及发布订阅模式和观察者模式
  22. On Vue responsive principle, publish subscribe mode and observer mode
  23. Xiaobai can understand it. It only takes 4 steps to solve the problem of Vue keep alive cache component
  24. Publish, subscribe and observer of design patterns
  25. Summary of common content added in ES6 + (II)
  26. No.8 Vue element admin learning (III) vuex learning and login method analysis
  27. Write a mini webpack project construction tool
  28. Shopping cart (front-end static page preparation)
  29. Introduction to the fluent platform
  30. Webpack5 cache
  31. The difference between drop-down box select option and datalist
  32. CSS review (III)
  33. Node.js学习笔记【七】
  34. Node.js learning notes [VII]
  35. Vue Router根据后台数据加载不同的组件(思考-&gt;实现-&gt;不止于实现)
  36. Vue router loads different components according to background data (thinking - & gt; Implementation - & gt; (more than implementation)
  37. 【JQuery框架,Java编程教程视频下载
  38. [jQuery framework, Java programming tutorial video download
  39. Vue Router根据后台数据加载不同的组件(思考-&gt;实现-&gt;不止于实现)
  40. Vue router loads different components according to background data (thinking - & gt; Implementation - & gt; (more than implementation)
  41. 【Vue,阿里P8大佬亲自教你
  42. 【Vue基础知识总结 5,字节跳动算法工程师面试经验
  43. [Vue, Ali P8 teaches you personally
  44. [Vue basic knowledge summary 5. Interview experience of byte beating Algorithm Engineer
  45. 【问题记录】- 谷歌浏览器 Html生成PDF
  46. [problem record] - PDF generated by Google browser HTML
  47. 【问题记录】- 谷歌浏览器 Html生成PDF
  48. [problem record] - PDF generated by Google browser HTML
  49. 【JavaScript】查漏补缺 —数组中reduce()方法
  50. [JavaScript] leak checking and defect filling - reduce() method in array
  51. 【重识 HTML (3),350道Java面试真题分享
  52. 【重识 HTML (2),Java并发编程必会的多线程你竟然还不会
  53. 【重识 HTML (1),二本Java小菜鸟4面字节跳动被秒成渣渣
  54. [re recognize HTML (3) and share 350 real Java interview questions
  55. [re recognize HTML (2). Multithreading is a must for Java Concurrent Programming. How dare you not
  56. [re recognize HTML (1), two Java rookies' 4-sided bytes beat and become slag in seconds
  57. 【重识 HTML ,nginx面试题阿里
  58. 【重识 HTML (4),ELK原来这么简单
  59. [re recognize HTML, nginx interview questions]
  60. [re recognize HTML (4). Elk is so simple