diff --git a/sources/tech/20181012 Command line quick tips- Reading files different ways.md b/sources/tech/20181012 Command line quick tips- Reading files different ways.md deleted file mode 100644 index 87e6e77d1e..0000000000 --- a/sources/tech/20181012 Command line quick tips- Reading files different ways.md +++ /dev/null @@ -1,120 +0,0 @@ -translating by distant1219 - -Command line quick tips: Reading files different ways -====== - -![](https://fedoramagazine.org/wp-content/uploads/2018/10/commandlinequicktips-816x345.jpg) - -Fedora is delightful to use as a graphical operating system. You can point and click your way through just about any task easily. But you’ve probably seen there is a powerful command line under the hood. To try it out in a shell, just open the Terminal application in your Fedora system. This article is one in a series that will show you some common command line utilities. - -In this installment you’ll learn how to read files in different ways. If you open a Terminal to do some work on your system, chances are good that you’ll need to read a file or two. - -### The whole enchilada - -The **cat** command is well known to terminal users. When you **cat** a file, you’re simply displaying the whole file to the screen. Really what’s happening under the hood is the file is read one line at a time, then each line is written to the screen. - -Imagine you have a file with one word per line, called myfile. To make this clear, the file will contain the word equivalent for a number on each line, like this: - -``` - - one - two - three - four - five - -``` - -So if you **cat** that file, you’ll see this output: - -``` - - $ cat myfile - one - two - three - four - five - -``` - -Nothing too surprising there, right? But here’s an interesting twist. You can also **cat** that file backward. For this, use the **tac** command. (Note that Fedora takes no blame for this debatable humor!) - -``` - - $ tac myfile - five - four - three - two - one - -``` - -The **cat** file also lets you ornament the file in different ways, in case that’s helpful. For instance, you can number lines: - -``` - - $ cat -n myfile - 1 one - 2 two - 3 three - 4 four - 5 five - -``` - -There are additional options that will show special characters and other features. To learn more, run the command **man cat** , and when done just hit **q** to exit back to the shell. - -### Picking over your food - -Often a file is too long to fit on a screen, and you may want to be able to go through it like a document. In that case, try the **less** command: - -``` - - $ less myfile - -``` - -You can use your arrow keys as well as **PgUp/PgDn** to move around the file. Again, you can use the **q** key to quit back to the shell. - -There’s actually a **more** command too, based on an older UNIX command. If it’s important to you to still see the file when you’re done, you might want to use it. The **less** command brings you back to the shell the way you left it, and clears the display of any sign of the file you looked at. - -### Just the appetizer (or dessert) - -Sometimes the output you want is just the beginning of a file. For instance, the file might be so long that when you **cat** the whole thing, the first few lines scroll past before you can see them. The **head** command will help you grab just those lines: - -``` - - $ head -n 2 myfile - one - two - -``` - -In the same way, you can use **tail** to just grab the end of a file: - -``` - - $ tail -n 3 myfile - three - four - five - -``` - -Of course these are only a few simple commands in this area. But they’ll get you started when it comes to reading files. - --------------------------------------------------------------------------------- - -via: https://fedoramagazine.org/commandline-quick-tips-reading-files-different-ways/ - -作者:[Paul W. Frields][a] -选题:[lujun9972][b] -译者:[译者ID](https://github.com/译者ID) -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/pfrields/ -[b]: https://github.com/lujun9972