Awk from entry to earth (12) awk can also write scripts to replace the shell

summary

And write shell The script is pretty much , First, the first line declares the interpreter path , For example, on my system ,awk The tool is installed in /user/bin/awk Catalog , So my awk The script starts with the following ：

#! /usr/bin/awk -f

The explanation of the above line is as follows ：

• #! , It's called Shi Pang , Indicate which interpreter is used to execute the commands in the script ;
• /usr/bin/awk , Interpreter ;
• -f , Interpreter options , Used to specify the program file to read ;

Say so , Now start with the following simple example , Let's delve into some executable awk Script . Create a new file using your favorite editor , Like this ：

$ vi script.awk

Then paste the following code into the file ：

#!/usr/bin/awk -f
BEGIN { printf "%s\n","Writing my first awk executable script!" }

Save the file and exit , Then execute the following command , Make the script executable ：

$ chmod +x script.awk

then , Execute it ：

$ ./script.awk

sample output ：

Writing my first awk executable script!

Add notes

A strict programmer will ask ：“ A comment? ？”. Yes , You can awk The script contains comments . Writing comments in code is a good programming habit . It helps other programmers read your code , Understand the function of each part of the program file or script . therefore , You can add comments to the script like this ：

#!/usr/bin/awk -f
#  How is this in  awk  An example of writing comments in 
#  Use special mode  BEGIN  To output a sentence 
BEGIN { printf "%s\n","Writing my first awk executable script!" }

Next, let's look at an example of reading a file . We want to get the account file /etc/passwd Find a person named aaronkilik Users of , Then print the user name like this 、 User ID、 User GID ：

The following is the content of our script file , The file named second.awk.

#! /usr/bin/awk -f
#  Use  BEGIN  Specify characters to set  FS  Built-in variables 
BEGIN { FS=":" }
#  Search for user name  aaronkilik  And output account details 
/aaronkilik/ { print "Username :",$1,"User ID :",$3,"User GID :",$4 }

Save the file and exit , Make the script executable , Then execute it like this ：

$ chmod +x second.awk
$ ./second.awk /etc/passwd

sample output ：

Username : aaronkilik User ID : 1000 User GID : 1000

In the last example below , We will use do while Statement to print numbers 0-10：

The following is the content of our script file , The file named do.awk.

#! /usr/bin/awk -f
#printing from 0-10 using a do while statement
#do while statement
BEGIN {
#initialize a counter
	x=0
	do {
		print x;
		x+=1;
	}while(x<=10)
}

After saving the file , Make the script executable as before . then , Run it ：

$ chmod +x do.awk
$ ./do.awk

sample output

0
1
2
3
4
5
6
7
8
9
10

summary

We have reached this wonderful awk The end of the series , I hope you have learned a lot from past articles , Think of these as you awk Introduction to programming language . I mentioned it from the beginning ,awk Is a complete text processing language , So you can learn a lot awk Other aspects of programming languages , For example, environment variables 、 Array 、 function （ Built in or user-defined ）, wait .