From f308e8f7ed975cad0b72879e0265b056eb647815 Mon Sep 17 00:00:00 2001 From: GHLandy Date: Fri, 20 Jan 2017 15:19:22 +0000 Subject: [PATCH] [Translated] How To Assign Output of a Linux Command to a Variable --- ...Output of a Linux Command to a Variable.md | 81 ------------------- ...Output of a Linux Command to a Variable.md | 81 +++++++++++++++++++ 2 files changed, 81 insertions(+), 81 deletions(-) delete mode 100644 sources/tech/20170119 How To Assign Output of a Linux Command to a Variable.md create mode 100644 translated/tech/20170119 How To Assign Output of a Linux Command to a Variable.md diff --git a/sources/tech/20170119 How To Assign Output of a Linux Command to a Variable.md b/sources/tech/20170119 How To Assign Output of a Linux Command to a Variable.md deleted file mode 100644 index beb1988956..0000000000 --- a/sources/tech/20170119 How To Assign Output of a Linux Command to a Variable.md +++ /dev/null @@ -1,81 +0,0 @@ -GHLandy Translating - -How To Assign Output of a Linux Command to a Variable -============================================================ - -When you run a command, it produces some kind of output: either the result of a program is suppose to produce or status/error messages of the program execution details. Sometimes, you may want to store the output of a command in a variable to be used in a later operation. - -In this post, we will review the different ways of assigning the output of a shell command to a variable, specifically useful for shell scripting purpose. - -To store the output of a command in a variable, you can use the shell command substitution feature in the forms below: - -``` -variable_name=$(command) -variable_name=$(command [option ...] arg1 arg2 ...) -OR -variable_name='command' -variable_name='command [option ...] arg1 arg2 ...' -``` - -Below are a few examples of using command substitution. - -In this first example, we will store the value of `who` (which shows who is logged on the system) command in the variable `CURRENT_USERS` user: - -``` -$ CURRENT_USERS=$(who) -``` - -Then we can use the variable in a sentence displayed using the [echo command][1] like so: - -``` -$ echo -e "The following users are logged on the system:\n\n $CURRENT_USERS" -``` - -In the command above: the flag `-e` means interpret any escape sequences ( such as `\n` for newline) used. To avoid wasting time as well as memory, simply perform the command substitution within the [echo command][2] as follows: - -``` -$ echo -e "The following users are logged on the system:\n\n $(who)" -``` -[ - ![Shows Current Logged Users in Linux](http://www.tecmint.com/wp-content/uploads/2017/01/Shows-Current-Logged-Users-in-Linux.png) -][3] - -Shows Current Logged Users in Linux - -Next, to demonstrate the concept using the second form; we can store the total number of files in the current working directory in a variable called `FILES` and echo it later as follows: - -``` -$ FILES=`sudo find . -type f -print | wc -l` -$ echo "There are $FILES in the current working directory." -``` -[ - ![Show Number of Files in Directory](http://www.tecmint.com/wp-content/uploads/2017/01/Show-Number-of-Files-in-Directory.png) -][4] - -Show Number of Files in Directory - -That’s it for now, in this article, we explained the methods of assigning the output of a shell command to a variable. You can add your thoughts to this post via the feedback section below. - --------------------------------------------------------------------------------- - -作者简介： - -![](http://1.gravatar.com/avatar/4e444ab611c7b8c7bcb76e58d2e82ae0?s=128&d=blank&r=g) - -Aaron Kili is a Linux and F.O.S.S enthusiast, an upcoming Linux SysAdmin, web developer, and currently a content creator for TecMint who loves working with computers and strongly believes in sharing knowledge. - --------------------------------------------------------------------------------- - -via: http://www.tecmint.com/assign-linux-command-output-to-variable/ - -作者：[Aaron Kili][a] -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]:http://www.tecmint.com/author/aaronkili/ -[1]:http://www.tecmint.com/echo-command-in-linux/ -[2]:http://www.tecmint.com/echo-command-in-linux/ -[3]:http://www.tecmint.com/wp-content/uploads/2017/01/Shows-Current-Logged-Users-in-Linux.png -[4]:http://www.tecmint.com/wp-content/uploads/2017/01/Show-Number-of-Files-in-Directory.png diff --git a/translated/tech/20170119 How To Assign Output of a Linux Command to a Variable.md b/translated/tech/20170119 How To Assign Output of a Linux Command to a Variable.md new file mode 100644 index 0000000000..d0dbe38b35 --- /dev/null +++ b/translated/tech/20170119 How To Assign Output of a Linux Command to a Variable.md @@ -0,0 +1,81 @@ +如何将 Linux 命令的输出赋值给变量 +================================== + +每当你运行一个命令，它都出在屏幕上输出一些内容：该命令的期望结果或者该命令执行细节的状态/错误消息。有些时候，你可能想要将某个命令的输出内容存储在一个变量中，以待在后续操作中取出来使用。 + +本文将介绍将 shell 命令赋值给变量的不同方法，这对于 shell 脚本编程是特别有用的。 + +你可以使用如下的 shell 命令置换特性来将命令的输出存储到变量中： + +``` +变量名=$(命令) +变量名=$(命令 [命令选项 ...] 参数1 参数2 ...) +或者: +变量名='命令' +变量名='命令 [命令选项 ...] 参数1 参数2 ...' +``` + +以下是使用命令置换特性的示例： + +本例，我们将 `who` (显示当前登录系统的用户) 的输出值存储到 `CURRENT_USERS` 变量中： + +``` +$ CURRENT_USERS=$(who) +``` + +然后，我们可以使用 [echo 命令][1] 来使用上述变量，如下： + +``` +$ echo -e "以下为登录到系统中的用户：\n\n $CURRENT_USERS" +``` + +上面的命令中：`-e` 标记表示解释所有的转义序列 (如 `\n` 为换行)。为节约时间和内存，通常在 [echo 命令][2] 中使用命令置换特性，如下： + +``` +$ echo -e "以下为登录到系统中的用户：\n\n $(who)" +``` + +[![显示当前登录系统的用户](http://www.tecmint.com/wp-content/uploads/2017/01/Shows-Current-Logged-Users-in-Linux.png)][3] + +在 Linux 中显示当前登录系统的用户 + +接下来，为了演示刚刚的第二种形式，我们以把当前工作目录下文件数存储到变量 `FILES` 为了，然后使用 echo 来输出，如下： + +``` +$ FILES=`sudo find . -type f -print | wc -l` +$ echo "当前目录有 $FILES 个文件。" +``` +[![显示目中包含文件的数量](http://www.tecmint.com/wp-content/uploads/2017/01/Show-Number-of-Files-in-Directory.png)][4] + +显示目中包含文件的数量 + +至此，文毕。我们展示了将 shell 命令的输出赋值给变量的方法。你可以在下边的评论反馈区留下你的想法。 + +--------------------------------------------------------- + +作者简介： + +![](http://1.gravatar.com/avatar/4e444ab611c7b8c7bcb76e58d2e82ae0?s=128&d=blank&r=g) + +Aaron Kili 是一名 Linux 和 F.O.S.S 忠实拥护者、高级 Linux 系统管理员、Web 开发者，目前在 TecMint 是一名活跃的博主，热衷于计算机并有着强烈的只是分享意愿。 +译者简介： + +![GHLandy](http://GHLandy.com/images/GHLandy.ico) + +[GHLandy](http://GHLandy.com) —— 欲得之，则为之奋斗 (If you want it, work for it.)。 + +------------------------------------------------ + +via: http://www.tecmint.com/assign-linux-command-output-to-variable/ + +作者：[Aaron Kili][a] +译者：[GHLandy](https://github.com/GHLandy) +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]:http://www.tecmint.com/author/aaronkili/ +[1]:http://www.tecmint.com/echo-command-in-linux/ +[2]:http://www.tecmint.com/echo-command-in-linux/ +[3]:http://www.tecmint.com/wp-content/uploads/2017/01/Shows-Current-Logged-Users-in-Linux.png +[4]:http://www.tecmint.com/wp-content/uploads/2017/01/Show-Number-of-Files-in-Directory.png