shell脚本学习指南_Shell脚本初学者指南：基础知识

Myth丶恋晨 2021-07-27 02:31 444阅读 0赞

![shell脚本学习指南][shell]

shell脚本学习指南

![banner-01][]

The term “shell scripting” gets mentioned often in Linux forums, but many users aren’t familiar with it. Learning this easy and powerful programming method can help you save time, learn the command-line better, and banish tedious file management tasks.

“ shell脚本”一词在Linux论坛中经常被提及，但是许多用户对此并不熟悉。 学习这种简单而强大的编程方法可以帮助您节省时间，更好地学习命令行并消除繁琐的文件管理任务。

## 什么是Shell脚本？ **(**What Is Shell Scripting?**)** ##

Being a Linux user means you play around with the command-line. Like it or not, there are just some things that are done much more easily via this interface than by pointing and clicking. The more you use and learn the command-line, the more you see its potential. Well, the command-line itself is a program: the shell. Most Linux distros today use Bash, and this is what you’re really entering commands into.

成为Linux用户意味着您需要使用命令行。 不管喜欢与否，通过此界面完成的某些事情要比指向和单击要容易得多。 您使用和学习命令行的次数越多，您看到的命令行的潜力就越大。 好吧，命令行本身就是一个程序：shell。 如今，大多数Linux发行版都使用Bash，而这正是您真正在其中输入命令的地方。

Now, some of you who used Windows before using Linux may remember batch files. These were little text files that you could fill with commands to execute and Windows would run them in turn. It was a clever and neat way to get some things done, like run games in your high school computer lab when you couldn’t open system folders or create shortcuts. Batch files in Windows, while useful, are a cheap imitation of shell scripts.

现在，在使用Linux之前使用Windows的某些人可能会记住批处理文件。 这些都是小的文本文件，您可以在其中填充要执行的命令，Windows会依次运行它们。 这是完成某些事情的一种巧妙而巧妙的方法，例如当您无法打开系统文件夹或创建快捷方式时，在高中计算机实验室中运行游戏。 Windows中的批处理文件虽然有用，但可以廉价地模仿Shell脚本。

![cbr script][]

Shell scripts allow us to program commands in chains and have the system execute them as a scripted event, just like batch files. They also allow for far more useful functions, such as command substitution. You can invoke a command, like date, and use it’s output as part of a file-naming scheme. You can automate backups and each copied file can have the current date appended to the end of its name. Scripts aren’t just invocations of commands, either. They’re programs in their own right. Scripting allows you to use programming functions – such as ‘for’ loops, if/then/else statements, and so forth – directly within your operating system’s interface. And, you don’t have to learn another language because you’re using what you already know: the command-line.

Shell脚本使我们可以对链中的命令进行编程，并使系统将其作为脚本事件执行，就像批处理文件一样。 它们还允许使用更多有用的功能，例如命令替换。 您可以调用日期之类的命令，并将其输出用作文件命名方案的一部分。 您可以自动执行备份，每个复制的文件都可以在其名称的末尾附加当前日期。 脚本也不只是命令的调用。 它们本身就是程序。 脚本允许您直接在操作系统界面内使用编程功能，例如“ for”循环，if / then / else语句等。 而且，您不必学习其他语言，因为您使用的是已知的命令行。

That’s really the power of scripting, I think. You get to program with commands you already know, while learning staples of most major programming languages. Need to do something repetitive and tedious? Script it! Need a shortcut for a really convoluted command? Script it! Want to build a really easy to use command-line interface for something? Script it!

我认为，这确实是脚本编写的力量。 在学习大多数主要编程语言的基础知识的同时，您可以使用已知的命令进行编程。 需要做一些重复且乏味的事情吗？ 编写脚本！ 需要真正复杂的命令的快捷方式？ 编写脚本！ 是否想为某个东西构建一个真正易于使用的命令行界面？ 编写脚本！

## 在你开始之前 **(**Before You Begin**)** ##

Before we begin our scripting series, let’s cover some basic information. We’ll be using the bash shell, which most Linux distributions use natively. Bash is available for Mac OS users and Cygwin on Windows, too. Since it’s so universal, you should be able to script regardless of your platform. In addition, so long as all of the commands that are referenced exist, scripts can work on multiple platforms with little to no tweaking required.

在开始编写脚本系列之前，让我们介绍一些基本信息。 我们将使用bash shell，大多数Linux发行版都使用bash shell。 Bash适用于Mac OS用户和Windows上的Cygwin。 由于它是如此通用，因此无论平台如何，您都应该能够编写脚本。 此外，只要所引用的所有命令都存在，脚本就可以在多个平台上运行，而几乎不需要调整。

Scripting can easily make use of “administrator” or “superuser” privileges, so it’s best to test out scripts before you put them to work. Also use common sense, like making sure you have backups of the files you’re about to run a script on. It’s also really important to use the right options, like –i for the rm command, so that your interaction is required. This can prevent some nasty mistakes. As such, read through scripts you download and be careful with data you have, just in case things go wrong.

脚本编写可以轻松利用“管理员”或“超级用户”特权，因此最好在使用脚本之前先对其进行测试。 也请使用常识，例如确保已备份要在其上运行脚本的文件。 使用正确的选项(例如–i用于rm命令)也非常重要，这样就需要进行交互。 这可以防止一些令人讨厌的错误。 因此，请通读下载的脚本，并谨慎使用所拥有的数据，以防万一出错。

At their core, scripts are just plain text files. You can use any text editor to write them: gedit, emacs, vim, nano… This list goes on. Just be sure to save it as plain text, not as rich text, or a Word document. Since I love the [ease of use that nano provides][], I’ll be using that.

脚本的核心只是纯文本文件。 您可以使用任何文本编辑器来编写它们：gedit，emacs，vim，nano…此列表不胜枚举。 只要确保将其另存为纯文本，而不是富文本或Word文档即可。 由于我喜欢[nano提供][ease of use that nano provides]的[易用性][ease of use that nano provides] ，因此我将继续使用它。

## 脚本权限和名称 **(**Script Permissions and Names**)** ##

Scripts are executed like programs, and in order for this to happen they need to have the proper permissions. You can make scripts executable by running the following command on it:

脚本像程序一样被执行，为了使这种情况发生，它们需要具有适当的权限。 您可以通过在脚本上运行以下命令来使脚本可执行：

> chmod +x ~/somecrazyfolder/script1
> 
> chmod + x〜/ somecrazyfolder / script1

This will allow anyone to run that particular script. If you want to restrict its use to just your user, you can use this instead:

这将允许任何人运行该特定脚本。 如果您希望将其仅用于您的用户，则可以使用以下方法：

> chmod u+x ~/somecrazyfolder/script1
> 
> chmod u + x〜/ somecrazyfolder / script1

In order to run this script, you would have to cd into the proper directory and then run the script like this:

为了运行此脚本，您必须将cd放入正确的目录，然后像这样运行脚本：

> cd ~/somecrazyfolder
> 
> cd〜/ somecrazyfolder
> 
> ./script1
> 
> ./script1

To make things more convenient, you can place scripts in a “bin” folder in your home directory:

为了方便起见，可以将脚本放在主目录中的“ bin”文件夹中：

> ~/bin
> 
> 〜/箱

In many modern distros, this folder no longer is created by default, but you can create it. This is usually where executable files are stored that belong to your user and not to other users. By placing scripts here, you can just run them by typing their name, just like other commands, instead of having to cd around and use the ‘./’ prefix.

在许多现代发行版中，默认情况下不再创建此文件夹，但是您可以创建它。 通常在这里存储属于您的用户而不是其他用户的可执行文件。 通过在此处放置脚本，您可以像输入其他命令一样通过键入其名称来运行它们，而不必使用cd并使用'./'前缀。

Before you name a script, though, you should the following command to check if you have a program installed that uses that name:

但是，在命名脚本之前，应使用以下命令检查是否安装了使用该名称的程序：

> which \[command\]
> 
> 哪个\[命令\]

A lot of people name their early scripts “test,” and when they try to run it in the command-line, nothing happens. This is because it conflicts with the test command, which does nothing without arguments. Always be sure your script names don’t conflict with commands, otherwise you may find yourself doing things you don’t intend to do!

很多人将他们早期的脚本命名为“测试”，当他们尝试在命令行中运行它时，什么也没有发生。 这是因为它与test命令冲突，后者没有参数就什么也不做。 始终确保脚本名称与命令不冲突，否则您可能会发现自己在做自己不打算做的事情！

## 脚本编写准则 **(**Scripting Guidelines**)** ##

![guidelines][]

As I mentioned before, every script file is essentially plain text. That doesn’t mean you can write what you want all willy-nilly, though. When a text file is attempted to be executed, shells will parse through them for clues as to whether they’re scripts or not, and how to handle everything properly. Because of this, there are a few guidelines you need to know.

如前所述，每个脚本文件基本上都是纯文本。 不过，这并不意味着您可以随意编写所有内容。 尝试执行文本文件时，shell将通过它们解析以获取有关它们是否为脚本以及如何正确处理所有内容的线索。 因此，您需要了解一些准则。

1.  Every script should being with “\#!/bin/bash”
    
    每个脚本都应带有“＃！/ bin / bash”
2.  Every new line is a new command
    
    每行都是新命令
3.  Comment lines start with a \#
    
    注释行以＃开头
4.  Commands are surrounded by ()
    
    命令被()包围

**The Hash-Bang Hack**

**哈希邦哈克**

When a shell parses through a text file, the most direct way to identify the file as a script is by making your first line:

当外壳程序解析文本文件时，将文件标识为脚本的最直接方法是通过第一行：

> \#!/bin/bash
> 
> ＃！/ bin / bash

If you use another shell, substitute its path here. Comment lines start with hashes (\#), but adding the bang (!) and the shell path after it is a sort of hack that will bypass this comment rule and will force the script to execute with the shell that this line points to.

如果您使用其他外壳，请在此处替换其路径。 注释行以哈希(＃)开头，但是在爆炸之后添加bang(！)和shell路径是一种hack，它将绕过此注释规则，并强制脚本以该行指向的shell执行。

**New Line = New Command**

**新行=新命令**

Every new line should be considered a new command, or a component of a larger system. If/then/else statements, for example, will take over multiple lines, but each component of that system is in a new line. Don’t let a command bleed over into the next line, as this can truncate the previous command and give you an error on the next line. If your text editor is doing that, you should turn off text-wrapping to be on the safe side. You can turn off text wrapping in nano bit hitting ALT+L.

每个新行都应被视为新命令，或者是更大系统的组成部分。 例如，if / then / else语句将接管多行，但是该系统的每个组件都在新行中。 不要让命令流到下一行，因为这会截断上一条命令，并在下一行给您一个错误。 如果您的文本编辑器正在执行此操作，则出于安全考虑，应关闭文本包装。 您可以按ALT + L的十亿分之一位关闭文本换行。

**Comment Often with \#s**

**常与\#s一起评论**

If you start a line with a \#, the line is ignored. This turns it into a comment line, where you can remind yourself of what the output of the previous command was, or what the next command will do. Again, turn off text wrapping, or break you comment into multiple lines that all begin with a hash. Using lots of comments is a good practice to keep, as it lets you and other people tweak your scripts more easily. The only exception is the aforementioned Hash-Bang hack, so don’t follow \#s with !s. ;-)

如果以＃开头，则忽略该行。 它将变成注释行，您可以在其中提醒自己上一条命令的输出是什么，或者下一条命令将执行什么操作。 同样，请关闭文本换行，或将注释分成多行，所有行均以哈希开头。 保留大量注释是一个好习惯，因为它使您和其他人可以更轻松地调整脚本。 唯一的例外是上述的Hash-Bang hack，因此请勿在\#s后面加上！s。 ;-)

**Commands Are Surrounded By Parentheses**

**命令用括号括起来**

In older days, command substitutions were done with single tick marks (\`, shares the ~ key). We’re not going to be touching on this yet, but as most people go off and explore after learning the basics, it’s probably a good idea to mention that you should use parentheses instead. This is mainly because when you nest – put commands inside other commands – parentheses work better.

在较早的日子里，命令替换是用单个刻度线来完成的(\`，共享〜键)。 我们还不会涉及到这一点，但是随着大多数人开始学习基础知识之后，提到应该改用括号可能是一个好主意。 这主要是因为当您将命令嵌套在其他命令中时，括号会更好。

## 您的第一个脚本 **(**Your First Script**)** ##

Let’s start with a simple script that allows you to copy files and append dates to the end of the filename. Let’s call it “datecp”. First, let’s check to see if that name conflicts with something:

让我们从一个简单的脚本开始，该脚本允许您复制文件并将日期附加到文件名的末尾。 我们称之为“ datecp”。 首先，让我们检查一下该名称是否与某些内容冲突：

![which cp][]

You can see that there’s no output of the which command, so we’re all set to use this name.

您会看到which命令没有输出，因此我们都已设置为使用此名称。

Let’s create a blank file in the ~/bin folder:

让我们在〜/ bin文件夹中创建一个空白文件：

> touch ~/bin/datecp
> 
> 触摸〜/ bin / datecp

![touch][]

And, let’s change the permission now, before we forget:

而且，在忘记之前，让我们现在更改权限：

![chmod][]

Let’s start building our script then. Open up that file in your text editor of choice. Like I said, I like the simplicity of nano.

然后让我们开始构建脚本。 在您选择的文本编辑器中打开该文件。 就像我说的，我喜欢nano的简单性。

> nano ~/bin/datecp
> 
> 纳米〜/ bin / datecp

And, let’s go ahead and put in the prerequisite first line, and a comment about what this script does.

并且，让我们继续进行操作，并在前提条件第一行中添加注释，并对此脚本的功能进行注释。

![hashbang hack][]

Next, let’s declare a variable. If you’ve ever taken algebra, you probably know what a that is. A variable allows us to store information and do things with it. Variables can “expand” when referenced elsewhere. That is, instead of displaying their name, they will display their stored contents. You can later tell that same variable to store different information, and any instruction that occurs after that will use the new information. It’s a really fancy placeholder.

接下来，让我们声明一个变量。 如果您曾经学习过代数，那么您可能知道那是什么。 变量使我们能够存储信息并使用它来做事。 变量在其他地方引用时可以“扩展”。 即，他们将不显示其名称，而是显示其存储的内容。 您以后可以告诉该变量存储不同的信息，此后发生的任何指令都将使用新信息。 这是一个非常漂亮的占位符。

What will we put in out variable? Well, let’s store the date and time! To do this, we’ll call upon the date command.

我们将输入什么变量？ 好吧，让我们存储日期和时间！ 为此，我们将调用date命令。

Take a look at the screenshot below for how to build the output of the date command:

查看以下屏幕截图，了解如何构建date命令的输出：

![date output][]

You can see that by adding different variables that start with %, you can change the output of the command to what you want. For more information, you can look at the manual page for the date command.

您可以看到，通过添加以％开头的不同变量，可以将命令的输出更改为所需的内容。 有关更多信息，请参见date命令的手册页。

Let’s use that last iteration of the date command, “date +%m\_%d\_%y-%H.%M.%S”, and use that in our script.

让我们使用date命令的最后一个迭代“ date +％m\_％d\_％y-％H.％M.％S”，并在脚本中使用它。

![date in script][]

If we were to save this script right now, we could run it and it would give us the output of the date command like we’d expect:

如果我们现在要保存此脚本，则可以运行它，它将像我们期望的那样为我们提供date命令的输出：

![date script output][]

But, let’s do something different. Let’s give a variable name, like date\_formatted to this command. The proper syntax for this is as follows:

但是，让我们做些不同的事情。 让我们给此命令指定一个变量名称，例如date\_formatted。 正确的语法如下：

> variable=$(command –options arguments)
> 
> 变量= $(命令–options参数)

And for us, we’d build it like this:

对于我们来说，我们将像这样构建它：

> date\_formatted=$(date +%m\_%d\_%y-%H.%M.%S)
> 
> date\_formatted = $(日期+％m\_％d\_％y-％H.％M.％S)

![date as variable][]

This is what we call command substitution. We’re essentially telling bash that whenever the variable “date\_formatted” shows up, to run the command inside the parentheses. Then, whatever output the commands gives should be displayed instead of the name of the variable, “date\_formatted”.

这就是我们所谓的命令替换。 我们实质上是在告诉bash，只要出现变量“ date\_formatted”，就在括号内运行命令。 然后，应显示命令给出的任何输出，而不是变量“ date\_formatted”的名称。

Here’s an example script and its output:

这是一个示例脚本及其输出：

![echo date script][]

![echo date output][]

Note that there are two spaces in the output. The space within the quotes of the echo command and the space in front of the variable are both displayed. Don’t use spaces if you don’t want them to show up. Also note that without this added “echo” line, the script would give absolutely no output.

请注意，输出中有两个空格。 都会显示echo命令的引号内的空格和变量前面的空格。 如果您不希望出现空格，请不要使用空格。 另请注意，如果没有添加此行的“ echo”行，该脚本将绝对不会提供任何输出。

Let’s get back to our script. Let’s next add in the copying part of the command.

让我们回到我们的脚本。 接下来让我们添加命令的复制部分。

> cp –iv $1 $2.$date\_formatted
> 
> cp –iv $ 1 $ 2. $ date\_formatted

![appended filename][]

This will invoke the copy command, with the –i and –v options. The former will ask you for verification before overwriting a file, and the latter will display what is being down on the command-line.

这将调用带有–i和–v选项的复制命令。 前者会在覆盖文件之前要求您进行验证，而后者将在命令行中显示正在关闭的内容。

Next, you can see I’ve added the “$1” option. When scripting, a dollar sign ($) followed by a number will denote that numbered argument of the script when it was invoked. For example, in the following command:

接下来，您可以看到我已经添加了“ $ 1”选项。 编写脚本时，美元符号($)后跟数字表示调用脚本时该编号的参数。 例如，在以下命令中：

> cp –iv Trogdor2.mp3 ringtone.mp3
> 
> cp –iv Trogdor2.mp3 ringtone.mp3

The first argument is “Trogdor2.mp3” and the second argument is “ringtone.mp3”.

第一个参数是“ Trogdor2.mp3”，第二个参数是“ ringtone.mp3”。

Looking back at our script, we can see that we’re referencing two arguments:

回顾一下脚本，我们可以看到我们在引用两个参数：

![appended filename][appended filename 1]

This means that when we run the script, we’ll need to provide two arguments for the script to run correctly. The first argument, $1, is the file that will be copied, and is substituted as the “cp –iv” command’s first argument.

这意味着在运行脚本时，我们需要提供两个参数以使脚本正确运行。 第一个参数$ 1是将被复制的文件，并被替换为“ cp –iv”命令的第一个参数。

The second argument, $2, will act as the output file for the same command. But, you can also see that it’s different. We’ve added a period and we’ve referenced the “date\_formatted” variable from above. Curious as to what this does?

第二个参数$ 2将用作同一命令的输出文件。 但是，您也可以看到它是不同的。 我们添加了一个句点，并从上面引用了“ date\_formatted”变量。 好奇这是做什么的？

Here’s what happens when the script is run:

运行脚本时会发生以下情况：

![appended filename output][]

You can see that the output file is listed as whatever I entered for $2, followed by a period, then the output of the date command! Makes sense, right?

您会看到输出文件被列为我为$ 2输入的内容，然后是句点，然后是date命令的输出！ 有道理吧？

Now when I run the datecp command, it will run this script and allow me to copy any file to a new location, and automatically add the date and time to end of the filename. Useful for archiving stuff!

现在，当我运行datecp命令时，它将运行此脚本，并允许我将任何文件复制到新位置，并自动将日期和时间添加到文件名的末尾。 对存档有用！

--------------------

Shell scripting is at the heart of making your OS work for you. You don’t have to learn a new programming language to make it happen, either. Try scripting with some basic commands at home and start thinking of what you can use this for.

Shell脚本是使操作系统适合您的核心。 您也不必学习新的编程语言即可实现它。 尝试在家中使用一些基本命令编写脚本，然后开始考虑可以将其用作什么。

Do you script? Have any advice for newbies? Share your thoughts in the comments! There’s more to come in this series!

你写剧本吗？ 对新手有什么建议吗？ 在评论区分享你的观点！ 这个系列还有更多内容！

> 翻译自: [https://www.howtogeek.com/67469/the-beginners-guide-to-shell-scripting-the-basics/][https_www.howtogeek.com_67469_the-beginners-guide-to-shell-scripting-the-basics]

shell脚本学习指南

[shell]: /images/20210726/33d2c2fd42cb42f383d394a2f2b3be8a.png
[banner-01]: /images/20210726/47822b0de46a4356919e588fb8566543.png
[cbr script]: /images/20210726/97f5bb1e43a442afa35af1489dca4a02.png
[ease of use that nano provides]: https://www.howtogeek.com/howto/42980/the-beginners-guide-to-nano-the-linux-command-line-text-editor/
[guidelines]: /images/20210726/9fd014791e184706be95dd24e782d4df.png
[which cp]: /images/20210726/6ba67b49973946f091ce19306b0c6a4e.png
[touch]: /images/20210726/133af227a2d3476a8fc10d2ac926f5ca.png
[chmod]: /images/20210726/c9ad84ae7d494294b5f0c170737d5b39.png
[hashbang hack]: /images/20210726/b2589378651c497c9f4f2473e92ab7b5.png
[date output]: /images/20210726/46d4fd71ede14c2db65dd53c75b4a9d7.png
[date in script]: /images/20210726/69c89e1e202e4a0f9d17ed4c6d7f153f.png
[date script output]: /images/20210726/9a87bdd9e4dd461a8c6cb855a54b0197.png
[date as variable]: /images/20210726/39cf3ddb67da416bbe140f8475bc3ccf.png
[echo date script]: /images/20210726/405a62152f4c4a919724fbd5814b027a.png
[echo date output]: /images/20210726/bd129482a156412098371b66d042feb8.png
[appended filename]: /images/20210726/f1c660ce01c845c28a05e4c240e38271.png
[appended filename 1]: /images/20210726/ce3b37bfaf424bce9cb32bef86a3a542.png
[appended filename output]: /images/20210726/91d339f7e96d48089f978c584c236254.png
[https_www.howtogeek.com_67469_the-beginners-guide-to-shell-scripting-the-basics]: https://www.howtogeek.com/67469/the-beginners-guide-to-shell-scripting-the-basics/