diff --git a/sources/tech/awk/Part 4 - How to Use Comparison Operators with Awk in Linux.md b/sources/tech/awk/Part 4 - How to Use Comparison Operators with Awk in Linux.md deleted file mode 100644 index 1d0ef007af..0000000000 --- a/sources/tech/awk/Part 4 - How to Use Comparison Operators with Awk in Linux.md +++ /dev/null @@ -1,97 +0,0 @@ -chunyang-wen translating - -How to Use Comparison Operators with Awk in Linux -=================================================== - -![](http://www.tecmint.com/wp-content/uploads/2016/05/Use-Comparison-Operators-with-AWK.png) - -When dealing with numerical or string values in a line of text, filtering text or strings using comparison operators comes in handy for Awk command users. - -In this part of the Awk series, we shall take a look at how you can filter text or strings using comparison operators. If you are a programmer then you must already be familiar with comparison operators but those who are not, let me explain in the section below. - -### What are Comparison operators in Awk? - -Comparison operators in Awk are used to compare the value of numbers or strings and they include the following: - -- `>` – greater than -- `<` – less than -- `>=` – greater than or equal to -- `<=` – less than or equal to -- `==` – equal to -- `!=` – not equal to -- `some_value ~ / pattern/` – true if some_value matches pattern -- `some_value !~ / pattern/` – true if some_value does not match pattern - -Now that we have looked at the various comparison operators in Awk, let us understand them better using an example. - -In this example, we have a file named food_list.txt which is a shopping list for different food items and I would like to flag food items whose quantity is less than or equal 20 by adding `(**)` at the end of each line. - -``` -File – food_list.txt -No Item_Name Quantity Price -1 Mangoes 45 $3.45 -2 Apples 25 $2.45 -3 Pineapples 5 $4.45 -4 Tomatoes 25 $3.45 -5 Onions 15 $1.45 -6 Bananas 30 $3.45 -``` - -The general syntax for using comparison operators in Awk is: - -``` -# expression { actions; } -``` - -To achieve the above goal, I will have to run the command below: - -``` -# awk '$3 <= 30 { printf "%s\t%s\n", $0,"**" ; } $3 > 30 { print $0 ;}' food_list.txt - -No Item_Name` Quantity Price -1 Mangoes 45 $3.45 -2 Apples 25 $2.45 ** -3 Pineapples 5 $4.45 ** -4 Tomatoes 25 $3.45 ** -5 Onions 15 $1.45 ** -6 Bananas 30 $3.45 ** -``` - -In the above example, there are two important things that happen: - -- The first expression `{ action ; }` combination, `$3 <= 30 { printf “%s\t%s\n”, $0,”**” ; }` prints out lines with quantity less than or equal to 30 and adds a `(**)` at the end of each line. The value of quantity is accessed using `$3` field variable. -- The second expression `{ action ; }` combination, `$3 > 30 { print $0 ;}` prints out lines unchanged since their quantity is greater then `30`. - -One more example: - -``` -# awk '$3 <= 20 { printf "%s\t%s\n", $0,"TRUE" ; } $3 > 20 { print $0 ;} ' food_list.txt - -No Item_Name Quantity Price -1 Mangoes 45 $3.45 -2 Apples 25 $2.45 -3 Pineapples 5 $4.45 TRUE -4 Tomatoes 25 $3.45 -5 Onions 15 $1.45 TRUE -6 Bananas 30 $3.45 -``` - -In this example, we want to indicate lines with quantity less or equal to 20 with the word (TRUE) at the end. - -### Summary - -This is an introductory tutorial to comparison operators in Awk, therefore you need to try out many other options and discover more. - -In case of any problems you face or any additions that you have in mind, then drop a comment in the comment section below. Remember to read the next part of the Awk series where I will take you through compound expressions. - --------------------------------------------------------------------------------- - -via: http://www.tecmint.com/comparison-operators-in-awk/ - -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/ diff --git a/translated/tech/awk/Part 4 - How to Use Comparison Operators with Awk in Linux.md b/translated/tech/awk/Part 4 - How to Use Comparison Operators with Awk in Linux.md new file mode 100644 index 0000000000..ef4f17f1d5 --- /dev/null +++ b/translated/tech/awk/Part 4 - How to Use Comparison Operators with Awk in Linux.md @@ -0,0 +1,95 @@ +在 Linux 下如何使用 Awk 比较操作符 +=================================================== + +![](http://www.tecmint.com/wp-content/uploads/2016/05/Use-Comparison-Operators-with-AWK.png) + +对于 Awk 命令的用户来说，处理一行文本中的数字或者字符串时，使用比较运算符来过滤文本和字符串是十分方便的。 + +在 Awk 系列的此部分中，我们将探讨一下如何使用比较运算符来过滤文本或者字符串。如果你是程序员，那么你应该已经熟悉比较运算符；对于其它人，下面的部分将介绍比较运算符。 + +### Awk 中的比较运算符是什么？ + +Awk 中的比较运算符用于比较字符串和或者数值，包括以下类型： + +- `>` – 大于 +- `<` – 小于 +- `>=` – 大于等于 +- `<=` – 小于等于 +- `==` – 等于 +- `!=` – 不等于 +- `some_value ~ / pattern/` – 如果some_value匹配模式pattern，则返回true +- `some_value !~ / pattern/` –如果some_value不匹配模式pattern，则返回true + +现在我们通过例子来熟悉 Awk 中各种不同的比较运算符。 + +在这个例子中，我们有一个文件名为 food_list.txt 的文件，里面包括不同食物的购买列表。我想给食物数量小于或等于30的物品所在行的后面加上`(**)` + +``` +File – food_list.txt +No Item_Name Quantity Price +1 Mangoes 45 $3.45 +2 Apples 25 $2.45 +3 Pineapples 5 $4.45 +4 Tomatoes 25 $3.45 +5 Onions 15 $1.45 +6 Bananas 30 $3.45 +``` + +Awk 中使用比较运算符的通用语法如下： + +``` +# expression { actions; } +``` + +为了实现刚才的目的，执行下面的命令： + +``` +# awk '$3 <= 30 { printf "%s\t%s\n", $0,"**" ; } $3 > 30 { print $0 ;}' food_list.txt + +No Item_Name` Quantity Price +1 Mangoes 45 $3.45 +2 Apples 25 $2.45 ** +3 Pineapples 5 $4.45 ** +4 Tomatoes 25 $3.45 ** +5 Onions 15 $1.45 ** +6 Bananas 30 $3.45 ** +``` + +在刚才的例子中，发生如下两件重要的事情： + +- 第一表达式 `{ action ; }` 组合， `$3 <= 30 { printf “%s\t%s\n”, $0,”**” ; }` 打印出数量小于等于30的行，并且在后面增加`(**)`。物品的数量是通过 `$3`这个域变量获得的。 +- 第二个表达式 `{ action ; }` 组合, `$3 > 30 { print $0 ;}` 原样输出数量小于等于 `30` 的行。 + +再举一个例子： + +``` +# awk '$3 <= 20 { printf "%s\t%s\n", $0,"TRUE" ; } $3 > 20 { print $0 ;} ' food_list.txt + +No Item_Name Quantity Price +1 Mangoes 45 $3.45 +2 Apples 25 $2.45 +3 Pineapples 5 $4.45 TRUE +4 Tomatoes 25 $3.45 +5 Onions 15 $1.45 TRUE +6 Bananas 30 $3.45 +``` + +在这个例子中，我们想通过在行的末尾增加 (TRUE) 来标记数量小于等于20的行。 + +### 总结 + +这是一篇对 Awk 中的比较运算符介绍性的指引，因此你需要尝试其他选项，发现更多使用方法。 + +如果你遇到或者想到任何问题，请在下面评论区留下评论。请记得阅读 Awk 系列下一部分的文章，那里我将介绍组合表达式。 + +-------------------------------------------------------------------------------- + +via: http://www.tecmint.com/comparison-operators-in-awk/ + +作者：[Aaron Kili][a] +译者：[chunyang-wen](https://github.com/chunyang-wen) +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/