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[#]: subject: "Bash Shell Scripting for beginners (Part 1)"
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[#]: via: "https://fedoramagazine.org/bash-shell-scripting-for-beginners-part-1/"
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[#]: author: "zexcon https://fedoramagazine.org/author/zexcon/"
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[#]: collector: "lujun9972"
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[#]: translator: "unigeorge"
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[#]: reviewer: " "
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[#]: publisher: " "
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[#]: url: " "
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Bash Shell Scripting for beginners (Part 1)
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======
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![][1]
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Photo by [N Bandaru][2] on [Unsplash][3]
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As the title implies this article will be covering Bash Shell Scripting at a beginner level. I’m not going to review the history of Bash but there are many resources to fill you in or you can visit the GNU project at <https://www.gnu.org/software/bash/>. We will start out with understanding some very basic concepts and then start to put things together.
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### Creating a script file
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The first thing to do is create a script file. First make sure the home directory is the current directory.
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```
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cd ~
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```
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In the home directory, create the example file. This can be named anything but _learnToScript.sh_ will be used in this article.
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```
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touch learnToScript.sh
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```
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From this point there will be a file called _learnToScript.sh_ in your home directory. Verify it exists and also notice the privileges for that file are -rw-rw-r– by typing the following.
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```
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ls -l
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```
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```
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[zexcon@trinity ~]$ ls -l
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total 7
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drwxr-xr-x. 1 zexcon zexcon 90 Aug 30 13:08 Desktop
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drwxr-xr-x. 1 zexcon zexcon 80 Sep 16 08:53 Documents
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drwxr-xr-x. 1 zexcon zexcon 1222 Sep 16 08:53 Downloads
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-rw-rw-r--. 1 zexcon zexcon 70 Sep 17 10:10 learnToScript.sh
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Music
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drwxr-xr-x. 1 zexcon zexcon 318 Sep 15 13:53 Pictures
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Public
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Videos
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[zexcon@trinity ~]$
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```
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There is one more thing that needs to be done to get started. Let’s try and execute the script with nothing written in it. Type the following:
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```
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./learnToScript.sh
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```
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```
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[zexcon ~]$ ./learnToScript.sh
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bash: ./learnToScript.sh: Permission denied
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```
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You get permission denied because there are no execute permissions on the file. You need to change the permissions of the file to be able to execute the script. If you are not familiar with permissions I would recommend reading the Fedora Magazine articles written by [Paul W. Frields][4]
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> [Command line quick tips: Permissions][5]
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> [Command line quick tips: More about permissions][6]
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At this point you’ve brushed up on permissions, so back to the terminal and let’s change the _learnToScript.sh_ file so it will execute. Type in the following to allow execution of the file.
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```
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chmod 755 learnToScript.sh
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```
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```
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[zexcon@trinity ~]$ ls -l
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total 7
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drwxr-xr-x. 1 zexcon zexcon 90 Aug 30 13:08 Desktop
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drwxr-xr-x. 1 zexcon zexcon 80 Sep 16 08:53 Documents
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drwxr-xr-x. 1 zexcon zexcon 1222 Sep 16 08:53 Downloads
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-rwxr-xr-x. 1 zexcon zexcon 70 Sep 17 10:10 learnToScript.sh
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Music
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drwxr-xr-x. 1 zexcon zexcon 318 Sep 15 13:53 Pictures
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Public
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Videos
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[zexcon@trinity ~]$
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```
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Okay now you’re ready, you have read, write and execute permissions (-rwxr-x r-x) to the _learnToScript.sh_ command.
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### Editing a script file
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Take a moment and make certain you are familiar with _vim_ or any text editor. Throughout this article I will be utilizing _vim_. At the command prompt type the following:
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```
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vim learnToScript.sh
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```
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This will bring you to an empty text file with a bunch of tildes in it. Type _i_ on your keyboard and this will move you into — INSERT — mode. You can see it’s in this mode by looking at the bottom left of the terminal window. (Note that an alternative editor is the [_nano_ editor][7].)
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From here you need to make sure that the file is recognized by the correct interpreter. So enter the shebang ( #! ) and the directory to your bash, /bin/bash:
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```
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#!/bin/bash
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```
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One last thing that you will use throughout the article is saving the document. Hit _Esc_ to leave input mode, then Shift + Colon. At the colon you will enter _wq_. This will write(_w_) the file and quit(_q_) _vim_ once you hit enter.
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A few things to remember while using _vi_m, anytime you want to write into a document you need to enter _i_ and you will see –INSERT– at the bottom. Anytime you want to save, you will need to hit _Esc_ to leave input mode, and then _Shift+:_ to enter _w_ to write the file or _Esc_ then _Shift+:_ to enter _q_ to quit and not save. Or add both _wq_ together and it will write and close. _Esc_ by itself will exit INSERT mode. You can find much more about _vim_ at it’s [website][8] or this [get started][9] site.
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## Lets start scripting…
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### echo
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The _echo_ command is used to return something to the terminal. You will notice that you can use single quotes, double quotes or no quotes. So let’s take a look at it with a traditional Hello World!
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```
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#!/bin/bash
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echo Hello World!
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echo 'Hello World!'
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echo "Hello World!"
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```
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```
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[zexcon ~]$ ./learnToScript.sh
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Hello World!
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Hello World!
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Hello World!
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[zexcon ~]$
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```
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Notice that you get the same result with all three options. This is not always the case but in this basic script it is. In some circumstances the type of quotes will make a difference. By the way, congratulations you have written your first Bash script. Let’s look at a few things that you will want to know as you continue to create more scripts and let your mind run wild.
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### Command Substitution $( ) or ` `
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Command substitution allows you to get the results of a command you might execute at the command line and write that result to a variable. For example if you type _ls_ at the command prompt you will get a list of the current working directory. So let’s put this into practice. You have two options for command substitution. Note that the first option uses a back tick found above the Tab key on the left side of the keyboard. It is paired with the tilde ~ key. The second option uses a shell variable.
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```
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#!/bin/bash
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command1=`ls`
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echo $command1
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command2=$(ls)
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echo $command2
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```
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```
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[zexcon ~]$ ./learnToScript.sh
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Desktop Documents Downloads learnToScript.sh Music Pictures Public snap Videos
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Desktop Documents Downloads learnToScript.sh Music Pictures Public snap Videos
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[zexcon ~]$
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```
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Notice no space between the variable, equal sign, and the start of the command. You get the exact same result with both options. Note that variables need to be led by a dollar sign. If you forget and you echo out the command variable without the dollar sign you will just see the name of the command as shown in the next example.
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```
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#!/bin/bash
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command1=`ls`
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echo command1
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command2=$(ls)
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echo command2
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```
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```
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[zexcon ~]$ ./learnToScript.sh
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command1
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command2
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[zexcon ~]$
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```
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### Double Parenthesis (())
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So what are double parenthesis for? Double parenthesis are simple, they are for mathematical equations.
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```
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#!/bin/bash
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echo $((5+3))
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echo $((5-3))
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echo $((5*3))
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echo $((5/3))
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```
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```
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[zexcon ~]$ ./learnToScript.sh
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8
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2
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15
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1
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[zexcon ~]$
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```
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## Conclusion
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At this point we have created our first script. We have an idea how to take several commands, place them in a script and run it to get the results. We will continue this discussion in the next article and look at redirection of input and output, the pipe command, using double brackets or maybe just adding some comments.
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--------------------------------------------------------------------------------
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via: https://fedoramagazine.org/bash-shell-scripting-for-beginners-part-1/
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作者：[zexcon][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/unigeorge)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://fedoramagazine.org/author/zexcon/
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[b]: https://github.com/lujun9972
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[1]: https://fedoramagazine.org/wp-content/uploads/2021/09/bash_shell_scripting_pt1-816x345.jpg
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[2]: https://unsplash.com/@nbandana?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText
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[3]: https://unsplash.com/s/photos/shell-scripting?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText
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[4]: http://pfrields.id.fedoraproject.org/
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[5]: https://fedoramagazine.org/command-line-quick-tips-permissions/
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[6]: https://fedoramagazine.org/command-line-quick-tips-more-about-permissions/
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[7]: https://fedoramagazine.org/gnu-nano-minimalist-console-editor/
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[8]: https://www.vim.org/docs.php
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[9]: https://linuxhandbook.com/basic-vim-commands/
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@ -0,0 +1,223 @@
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[#]: subject: "Bash Shell Scripting for beginners (Part 1)"
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[#]: via: "https://fedoramagazine.org/bash-shell-scripting-for-beginners-part-1/"
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[#]: author: "zexcon https://fedoramagazine.org/author/zexcon/"
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[#]: collector: "lujun9972"
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[#]: translator: "unigeorge"
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[#]: reviewer: " "
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[#]: publisher: " "
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[#]: url: " "
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Bash Shell 脚本新手指南（第一部分）
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======
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![][1]
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Photo by [N Bandaru][2] on [Unsplash][3]
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如标题所示，本文将涵盖面向初学者的 Bash Shell 脚本知识。虽然本文没有回顾 Bash 的历史，但是有很多资源能够便于读者了解相关内容，读者也可以直接访问 <https://www.gnu.org/software/bash/> 上的 GNU 项目。我们会从了解一些非常基本的概念开始，然后再将相关知识综合起来。
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### 创建脚本文件
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首先来创建一个脚本文件。我们要确保当前目录为家目录。
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```
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cd ~
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```
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在主目录中创建示例文件。文件名可以是任意名称，本文使用 _learnToScript.sh_ 作为文件名。
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```
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touch learnToScript.sh
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```
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此时家目录中就生成了一个名为 _learnToScript.sh_ 的文件。输入以下命令以检验该文件是否存在，还可以注意到其权限是 -rw-rw-r–。
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```
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ls -l
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```
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```
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[zexcon@trinity ~]$ ls -l
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total 7
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drwxr-xr-x. 1 zexcon zexcon 90 Aug 30 13:08 Desktop
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drwxr-xr-x. 1 zexcon zexcon 80 Sep 16 08:53 Documents
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drwxr-xr-x. 1 zexcon zexcon 1222 Sep 16 08:53 Downloads
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-rw-rw-r--. 1 zexcon zexcon 70 Sep 17 10:10 learnToScript.sh
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Music
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drwxr-xr-x. 1 zexcon zexcon 318 Sep 15 13:53 Pictures
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Public
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Videos
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[zexcon@trinity ~]$
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```
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正式开始之前还有一件事要做。可以试一下在没有写入任何内容的情况下执行脚本，命令行输入以下内容：
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```
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./learnToScript.sh
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```
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```
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[zexcon ~]$ ./learnToScript.sh
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bash: ./learnToScript.sh: Permission denied
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```
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提示权限被拒绝，因为该文件没有执行权限。所以你需要更改文件的权限才能执行脚本。如果你不熟悉权限相关知识，建议阅读 [Paul W. Frields][4] 写的 Fedora 杂志文章。
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> [Command line quick tips: Permissions][5]
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> [Command line quick tips: More about permissions][6]
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假定我们已经了解了权限相关知识，回到终端更改 _learnToScript.sh_ 文件，增加执行权限。输入以下内容：
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```
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chmod 755 learnToScript.sh
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```
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```
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[zexcon@trinity ~]$ ls -l
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total 7
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drwxr-xr-x. 1 zexcon zexcon 90 Aug 30 13:08 Desktop
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||||
drwxr-xr-x. 1 zexcon zexcon 80 Sep 16 08:53 Documents
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drwxr-xr-x. 1 zexcon zexcon 1222 Sep 16 08:53 Downloads
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-rwxr-xr-x. 1 zexcon zexcon 70 Sep 17 10:10 learnToScript.sh
|
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Music
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drwxr-xr-x. 1 zexcon zexcon 318 Sep 15 13:53 Pictures
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drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Public
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||||
drwxr-xr-x. 1 zexcon zexcon 0 Jul 7 16:04 Videos
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[zexcon@trinity ~]$
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```
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好的，现在一切准备就绪，你已经获得了 _learnToScript.sh_ 命令的读取、写入和执行权限 (-rwxr-xr-x)。
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### 编辑脚本文件
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下面的内容需要你熟悉 _vim_ 或其他类似的文本编辑器，本文选用 _vim_。在命令提示符下输入以下内容：
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```
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vim learnToScript.sh
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```
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这会打开一个空的文本文件，里面有一堆波浪号。键盘输入 _i_ 将进入 — INSERT — 模式。通过查看终端窗口的左下角，你可以确认它处于该模式。（友情推荐 [_nano_ editor][7] 编辑器也很不错。）
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接下来我们要确保文件被正确的解释器识别。因此，输入 #! 和 bash 的目录 /bin/bash：
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```
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#!/bin/bash
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```
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本文教程步骤的最后一件事是保存文档。按 _Esc_ 退出输入模式，然后按 Shift + 冒号。在冒号处输入 _wq_，按下回车键，就会写入（_w_）文件并退出（_q_）_vim_编辑器。
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使用 _vim_ 时要记住，要想写入文档，就需要输入 _i_，此时你会在底部看到 –INSERT–。要保存文档，就需要按 _Esc_ 退出输入模式，然后按 _Shift+:_，输入 _w_ 写入文件；或者按 _Esc_，然后 _Shift+:_ 输入 _q_，实现退出而不保存；或者将 _wq_ 加在一起，可以实现写入并关闭文件。_Esc_ 本身就只是退出插入模式。您可以在 [官方网站][8] 或 [教程网站][9] 上找到更多关于 _vim_ 的信息。
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## 开始正式写脚本
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### echo 命令
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_echo_ 命令用于向终端返回一些信息，可以使用单引号、双引号或不使用引号。那么让我们用一个传统的 Hello World 来试试它！
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||||
```
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||||
#!/bin/bash
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||||
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||||
echo Hello World!
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||||
echo 'Hello World!'
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||||
echo "Hello World!"
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||||
```
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||||
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||||
```
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||||
[zexcon ~]$ ./learnToScript.sh
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Hello World!
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||||
Hello World!
|
||||
Hello World!
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||||
[zexcon ~]$
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||||
```
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||||
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注意，上述三行得到了相同的结果。使用单引号、双引号或不使用引号的结果不是一定相同的，但在这个基本脚本中确实得到了同样的结果。在某些情况下，引号的类型不同会导致结果差异。至此恭喜你编写了第一个 Bash 脚本。当你继续创建更多脚本并放飞你的想法时，可能会需要了解以下更多的知识。
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### 命令替换 $( ) 和 ` `
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||||
命令替换可以实现以下效果：获取在命令行执行命令的结果，并将该结果写入变量。例如，如果在命令提示符下输入 _ls_，可以获得当前工作目录的列表。我们用这个命令来实践一下。命令替换选项有两个，请注意：第一个选项使用键盘左侧 Tab 键上方的反引号。它与波浪号 ~ 在一个键位上。第二个选项使用 shell 变量。
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||||
```
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||||
#!/bin/bash
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||||
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||||
command1=`ls`
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||||
echo $command1
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||||
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||||
command2=$(ls)
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||||
echo $command2
|
||||
```
|
||||
|
||||
```
|
||||
[zexcon ~]$ ./learnToScript.sh
|
||||
Desktop Documents Downloads learnToScript.sh Music Pictures Public snap Videos
|
||||
Desktop Documents Downloads learnToScript.sh Music Pictures Public snap Videos
|
||||
[zexcon ~]$
|
||||
```
|
||||
|
||||
注意变量、等号和命令开头之间不要有空格。使用这两个选项得到的结果是完全相同的。请注意，变量需要以美元符号开头。如果你忘记了，并且 echo 了不带美元符号的命令变量，会只输出命令的名称，如下所示。
|
||||
|
||||
```
|
||||
#!/bin/bash
|
||||
|
||||
command1=`ls`
|
||||
echo command1
|
||||
|
||||
command2=$(ls)
|
||||
echo command2
|
||||
```
|
||||
|
||||
```
|
||||
[zexcon ~]$ ./learnToScript.sh
|
||||
command1
|
||||
command2
|
||||
[zexcon ~]$
|
||||
```
|
||||
|
||||
### 双括号 (())
|
||||
|
||||
那么双括号有什么用呢？ 很简单，双括号用于数学方程式。
|
||||
|
||||
```
|
||||
#!/bin/bash
|
||||
|
||||
echo $((5+3))
|
||||
echo $((5-3))
|
||||
echo $((5*3))
|
||||
echo $((5/3))
|
||||
```
|
||||
|
||||
```
|
||||
[zexcon ~]$ ./learnToScript.sh
|
||||
8
|
||||
2
|
||||
15
|
||||
1
|
||||
[zexcon ~]$
|
||||
```
|
||||
|
||||
## 结语
|
||||
|
||||
至此，我们已经创建了第一个脚本。我们知道了如何执行多个命令：将它们放在一个脚本中并运行，就可以获得结果。下一篇文章会继续讨论，了解输入和输出的重定向、管道命令、使用双括号或者添加注释等知识。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://fedoramagazine.org/bash-shell-scripting-for-beginners-part-1/
|
||||
|
||||
作者：[zexcon][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[unigeorge](https://github.com/unigeorge)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://fedoramagazine.org/author/zexcon/
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://fedoramagazine.org/wp-content/uploads/2021/09/bash_shell_scripting_pt1-816x345.jpg
|
||||
[2]: https://unsplash.com/@nbandana?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText
|
||||
[3]: https://unsplash.com/s/photos/shell-scripting?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText
|
||||
[4]: http://pfrields.id.fedoraproject.org/
|
||||
[5]: https://fedoramagazine.org/command-line-quick-tips-permissions/
|
||||
[6]: https://fedoramagazine.org/command-line-quick-tips-more-about-permissions/
|
||||
[7]: https://fedoramagazine.org/gnu-nano-minimalist-console-editor/
|
||||
[8]: https://www.vim.org/docs.php
|
||||
[9]: https://linuxhandbook.com/basic-vim-commands/
|
||||
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Reference in New Issue
Block a user