From 05955ce3dad0be7b4f8513802ca63d3b80e1deed Mon Sep 17 00:00:00 2001 From: HankChow <280630620@qq.com> Date: Wed, 10 Apr 2019 21:48:59 +0800 Subject: [PATCH] hankchow translated --- ...6 Using Square Brackets in Bash- Part 1.md | 154 ------------------ ...6 Using Square Brackets in Bash- Part 1.md | 149 +++++++++++++++++ 2 files changed, 149 insertions(+), 154 deletions(-) delete mode 100644 sources/tech/20190326 Using Square Brackets in Bash- Part 1.md create mode 100644 translated/tech/20190326 Using Square Brackets in Bash- Part 1.md diff --git a/sources/tech/20190326 Using Square Brackets in Bash- Part 1.md b/sources/tech/20190326 Using Square Brackets in Bash- Part 1.md deleted file mode 100644 index ea54fdabed..0000000000 --- a/sources/tech/20190326 Using Square Brackets in Bash- Part 1.md +++ /dev/null @@ -1,154 +0,0 @@ -[#]: collector: (lujun9972) -[#]: translator: (HankChow) -[#]: reviewer: ( ) -[#]: publisher: ( ) -[#]: url: ( ) -[#]: subject: (Using Square Brackets in Bash: Part 1) -[#]: via: (https://www.linux.com/blog/2019/3/using-square-brackets-bash-part-1) -[#]: author: (Paul Brown https://www.linux.com/users/bro66) - -Using Square Brackets in Bash: Part 1 -====== - -![square brackets][1] - -This tutorial tackle square brackets and how they are used in different contexts at the command line. - -[Creative Commons Zero][2] - -After taking a look at [how curly braces (`{}`) work on the command line][3], now it’s time to tackle brackets (`[]`) and see how they are used in different contexts. - -### Globbing - -The first and easiest use of square brackets is in _globbing_. You have probably used globbing before without knowing it. Think of all the times you have listed files of a certain type, say, you wanted to list JPEGs, but not PNGs: - -``` -ls *.jpg -``` - -Using wildcards to get all the results that fit a certain pattern is precisely what we call globbing. - -In the example above, the asterisk means " _zero or more characters_ ". There is another globbing wildcard, `?`, which means " _exactly one character_ ", so, while - -``` -ls d*k* -``` - -will list files called _darkly_ and _ducky_ (and _dark_ and _duck_ \-- remember `*` can also be zero characters), - -``` -ls d*k? -``` - -will not list _darkly_ (or _dark_ or _duck_ ), but it will list _ducky_. - -Square brackets are used in globbing for sets of characters. To see what this means, make directory in which to carry out tests, `cd` into it and create a bunch of files like this: - -``` -touch file0{0..9}{0..9} -``` - -(If you don't know why that works, [take a look at the last installment that explains curly braces `{}`][3]). - -This will create files _file000_ , _file001_ , _file002_ , etc., through _file097_ , _file098_ and _file099_. - -Then, to list the files in the 70s and 80s, you can do this: - -``` -ls file0[78]? -``` - -To list _file022_ , _file027_ , _file028_ , _file052_ , _file057_ , _file058_ , _file092_ , _file097_ , and _file98_ you can do this: - -``` -ls file0[259][278] -``` - -Of course, you can use globbing (and square brackets for sets) for more than just `ls`. You can use globbing with any other tool for listing, removing, moving, or copying files, although the last two may require a bit of lateral thinking. - -Let's say you want to create duplicates of files _file010_ through _file029_ and call the copies _archive010_ , _archive011_ , _archive012_ , etc.. - -You can't do: - -``` -cp file0[12]? archive0[12]? -``` - -Because globbing is for matching against existing files and directories and the _archive..._ files don't exist yet. - -Doing this: - -``` -cp file0[12]? archive0[1..2][0..9] -``` - -won't work either, because `cp` doesn't let you copy many files to other many new files. Copying many files only works if you are copying them to a directory, so this: - -``` -mkdir archive - -cp file0[12]? archive -``` - -would work, but it would copy the files, using their same names, into a directory called _archive/_. This is not what you set out to do. - -However, if you look back at [the article on curly braces (`{}`)][3], you will remember how you can use `%` to lop off the end of a string contained in a variable. - -Of course, there is a way you can also lop of the beginning of string contained in a variable. Instead of `%`, you use `#`. - -For practice, you can try this: - -``` -myvar="Hello World" - -echo Goodbye Cruel ${myvar#Hello} -``` - -It prints " _Goodbye Cruel World_ " because `#Hello` gets rid of the _Hello_ part at the beginning of the string stored in `myvar`. - -You can use this feature alongside your globbing tools to make your _archive_ duplicates: - -``` -for i in file0[12]?;\ - -do\ - -cp $i archive${i#file};\ - -done -``` - -The first line tells the Bash interpreter that you want to loop through all the files that contain the string _file0_ followed by the digits _1_ or _2_ , and then one other character, which can be anything. The second line `do` indicates that what follows is the instruction or list of instructions you want the interpreter to loop through. - -Line 3 is where the actually copying happens, and you use the contents of the loop variable _`i`_ **twice: First, straight out, as the first parameter of the `cp` command, and then you add _archive_ to its contents, while at the same time cutting of _file_. So, if _`i`_ contains, say, _file019_... - -``` -"archive" + "file019" - "file" = "archive019" -``` - -the `cp` line is expanded to this: - -``` -cp file019 archive019 -``` - -Finally, notice how you can use the backslash `\` to split a chain of commands over several lines for clarity. - -In part two, we’ll look at more ways to use square brackets. Stay tuned. - --------------------------------------------------------------------------------- - -via: https://www.linux.com/blog/2019/3/using-square-brackets-bash-part-1 - -作者：[Paul Brown][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://www.linux.com/users/bro66 -[b]: https://github.com/lujun9972 -[1]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/square-gabriele-diwald-475007-unsplash.jpg?itok=cKmysLfd (square brackets) -[2]: https://www.linux.com/LICENSES/CATEGORY/CREATIVE-COMMONS-ZERO -[3]: https://www.linux.com/blog/learn/2019/2/all-about-curly-braces-bash diff --git a/translated/tech/20190326 Using Square Brackets in Bash- Part 1.md b/translated/tech/20190326 Using Square Brackets in Bash- Part 1.md new file mode 100644 index 0000000000..b095e4d291 --- /dev/null +++ b/translated/tech/20190326 Using Square Brackets in Bash- Part 1.md @@ -0,0 +1,149 @@ +[#]: collector: (lujun9972) +[#]: translator: (HankChow) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Using Square Brackets in Bash: Part 1) +[#]: via: (https://www.linux.com/blog/2019/3/using-square-brackets-bash-part-1) +[#]: author: (Paul Brown https://www.linux.com/users/bro66) + +在 Bash 中使用方括号 [第 1 节] +====== + +![square brackets][1] + +> 这篇文章将要介绍方括号及其在命令行中的用法。 + +看完[花括号在命令行中的用法][3]之后，现在我们继续来看方括号（`[]`）在上下文中是如何发挥作用的。 + +### 通配Globbing + +方括号最简单的用法就是通配。你可能在知道“通配”这个概念之前就已经通过通配来匹配内容了，列出具有相同特征的多个文件就是一个很常见的场景，例如列出所有 JPEG 文件： + +``` +ls *.jpg +``` + +使用通配符wildcard来得到符合某个模式的所有内容，这个过程就叫通配。 + +在上面的例子当中，星号（`*`）就代表“0 个或多个字符”。除此以外，还有代表“有且仅有一个字符”的问号（`?`）。因此 + +``` +ls d*k* +``` + +可以列出 `darkly` 和 `ducky`，而且 `dark` 和 `duck` 也是可以被列出的，因为 `*` 可以匹配 0 个字符。而 + +``` +ls d*k? +``` + +则只能列出 `ducky`，不会列出 `darkly`、`dark` 和 `duck`。 + +方括号也可以用于通配。为了便于演示，可以创建一个用于测试的目录，并在这个目录下创建文件： + +``` +touch file0{0..9}{0..9} +``` + +（如果你还不清楚上面这个命令的原理，可以看一下[另一篇介绍花括号的文章][3]） + +执行上面这个命令之后，就会创建 `file000`、`file001`、……、`file099` 这 100 个文件。 + +如果要列出这些文件当中第二位数字是 7 或 8 的文件，可以执行： + +``` +ls file0[78]? +``` + +如果要列出 `file022`、`file027`、`file028`、`file052`、`file057`、`file058`、`file092`、`file097`、`file098`，可以执行： + +``` +ls file0[259][278] +``` + +当然，不仅仅是 `ls`，很多其它的命令行工具都可以使用方括号来进行通配操作。但在删除文件、移动文件、复制文件的过程中使用通配，你需要有一点横向思维。 + +例如将 `file010` 到 `file029` 这 30 个文件复制成 `archive010` 到 `archive029` 这 30 个副本，不可以这样执行： + +``` +cp file0[12]? archive0[12]? +``` + +因为通配只能针对已有的文件，而 archive 开头的文件并不存在，不能进行通配。 + +而这条命令 + +``` +cp file0[12]? archive0[1..2][0..9] +``` + +也同样不行，因为 `cp` 并不允许将多个文件复制到多个文件。在复制多个文件的情况下，只能将多个文件复制到一个指定的目录下： + +``` +mkdir archive + +cp file0[12]? archive +``` + +这条命令是可以正常运行的，但它只会把这 30 个文件以同样的名称复制到 `archive/` 目录下，而这并不是我们想要的效果。 + +如果你阅读过我[关于花括号的文章][3]，你大概会记得可以使用 `%` 来截掉字符串的末尾部分，而使用 `#` 则可以截掉字符串的开头部分。 + +例如： + +``` +myvar="Hello World" + +echo Goodbye Cruel ${myvar#Hello} +``` + +就会输出 `Goodbye Cruel World`，因为 `#Hello` 将 `myvar` 变量中开头的 `Hello` 去掉了。 + +在通配的过程中，也可以使用这一个技巧。 + +``` +for i in file0[12]?;\ + +do\ + +cp $i archive${i#file};\ + +done +``` + +上面的第一行命令告诉 Bash 需要对所有 `file01` 开头或者 `file02` 开头，且后面只跟一个任意字符的文件进行操作，第二行的 `do` 和第四行的 `done` 代表需要对这些文件都执行这一块中的命令。 + +第三行就是实际的复制操作了，这里使用了两次 `$i` 变量：第一次在 `cp` 命令中直接作为源文件的文件名使用，第二次则是截掉文件名开头的 `file` 部分，然后在开头补上一个 `archive`，也就是这样： + +``` +"archive" + "file019" - "file" = "archive019" +``` + +最终整个 `cp` 命令是这样的： + +``` +cp file019 archive019 +``` + +最后，顺带说明一下反斜杠 `\` 的作用是将一条长命令拆分成多行，这样可以方便阅读。 + +在下一节，我们会了解方括号的更多用法，敬请关注。 + +-------------------------------------------------------------------------------- + +via: https://www.linux.com/blog/2019/3/using-square-brackets-bash-part-1 + +作者：[Paul Brown][a] +选题：[lujun9972][b] +译者：[HankChow](https://github.com/HankChow) +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://www.linux.com/users/bro66 +[b]: https://github.com/lujun9972 +[1]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/square-gabriele-diwald-475007-unsplash.jpg?itok=cKmysLfd "square brackets" +[2]: https://www.linux.com/LICENSES/CATEGORY/CREATIVE-COMMONS-ZERO +[3]: https://www.linux.com/blog/learn/2019/2/all-about-curly-braces-bash +