linux中awk命令

AWK is suitable for pattern search and processing. The script runs to search one or more files to identify matching patterns and if the said patterns perform specific tasks. In this guide, we take a look into AWK Linux command and see what it can do.

AWK适用于模式搜索和处理。 该脚本运行以搜索一个或多个文件以识别匹配的模式，以及所述模式是否执行特定任务。 在本指南中，我们研究了AWK Linux命令并了解它可以做什么。

AWK可以执行哪些操作？ (What Operations can AWK do?)

• Scanning files line by line逐行扫描文件
• Splitting each input line into fields将每条输入线分成多个字段
• Comparing input lines and fields to patterns比较输入行和字段与模式
• Performing specified actions on matching lines在匹配行上执行指定的操作

AWK命令的实用性 (AWK Command Usefulness)

• Changing data files更改数据文件
• Producing formatted reports生成格式化的报告

awk命令的编程概念 (Programming Concepts for awk command)

• Format output lines格式化输出行
• Conditional and loops条件循环
• Arithmetic and string operations算术和字符串运算

AWK语法 (AWK Syntax)

$ awk options 'selection _criteria {action }' input-file > output-file

To demonstrate more about AWK usage, we are going to use the text file called file.txt

为了演示有关AWK用法的更多信息，我们将使用名为file.txt的文本文件。

1st column => Item,
2nd column => Model
3rd column => Country
4th column => Cost

第一栏=>项目，
第二列=>型号
第三栏=>国家
第四列=>费用

Awk命令示例 (Awk Command Examples)

打印特定列 (Printing specific columns)

To print the 2nd and 3rd columns, execute the command below.

要打印第二列和第三列，请执行以下命令。

$ awk '{print $2 "\t" $3}' file.txt

Output

输出量

打印文件中的所有行 (Printing all lines in a file)

If you wish to list all the lines and columns in a file, execute

如果要列出文件中的所有行和列，请执行

$ awk ' {print $0}' file.txt

Output

输出量

打印与特定图案匹配的所有行 (Printing all lines that match a specific pattern)

if you want to print lines that match a certain pattern, the syntax is as shown

如果要打印与特定模式匹配的行，则语法如下所示

$ awk '/variable_to_be_matched/ {print $0}' file.txt

For instance, to match all entries with the letter ‘o’, the syntax will be

例如，要匹配所有带有字母“ o”的条目，语法为

$ awk '/o/ {print $0}' file.txt

Output

输出量

To match all entries with the letter ‘e’

使所有条目与字母“ e”匹配

$ awk '/e/ {print $0}' file.txt

Output

输出量

打印与特定图案匹配的列 (Printing columns that match a specific pattern)

When AWK locates a pattern match, the command will execute the whole record. You can change the default by issuing an instruction to display only certain fields.

当AWK找到一个模式匹配项时，该命令将执行整个记录。 您可以通过发出仅显示某些字段的指令来更改默认值。

For example:

例如：

$ awk '/a/ {print $3 "\t" $4}' file.txt

The above command prints the 3rd and 4th columns where the letter ‘a’ appears in either of the columns

上面的命令将打印第三和第四列，其中字母“ a”出现在任一列中

Output

输出量

计数和打印匹配图案 (Counting and Printing Matched Pattern)

You can use AWK to count and print the number of lines for every pattern match. For example, the command below counts the number of instances a matching pattern appears

您可以使用AWK来计数和打印每个模式匹配的行数。 例如，以下命令计算匹配模式出现的实例数

$ awk '/a/{++cnt} END {print "Count = ", cnt}' file.txt

Output

输出量

打印行数多于或少于字符数 (Print Lines with More or less than a No. of Characters)

AWK has a built-in length function that returns the length of the string. From the command $0 variable stores the entire line and in the absence of a body block, the default action is taken, i.e., the print action. Therefore, in our text file, if a line has more than 18 characters, then the comparison results true, and the line is printed as shown below.

AWK具有内置的长度函数，该函数返回字符串的长度。 从命令$ 0变量存储整行，并且在没有主体块的情况下，将采取默认操作，即打印操作。 因此，在我们的文本文件中，如果一行中的字符超过18个，则比较结果为true，并且该行将如下所示打印。

$ awk 'length($0) > 20' file.txt

Output

输出量

将AWK的输出保存到其他文件 (Saving output of AWK to a different file)

If you wish to save the output of your results, use the > redirection operator. For example

如果希望保存结果输出，请使用>重定向运算符。 例如

$ awk '/a/ {print $3 "\t" $4}' file.txt > Output.txt

You can verify the results using the cat command as shown below

您可以使用cat命令验证结果，如下所示

$ cat output.txt

Output

输出量

结论 (Conclusion)

AWK is another simple programming script that you can use to manipulate text in documents or perform specific functions. The shared commands are a few or the many you are yet to know or come across.

AWK是另一个简单的编程脚本，可用于处理文档中的文本或执行特定功能。 共享命令是您尚不知道或遇到的几个命令。

翻译自: https://www.journaldev.com/24871/awk-command-linux-unix

linux中awk命令