Score:0

Server

Variable in AWK

serverstackqns

11/11/23, 1:10 PM

How can I add a variable within awk command? below is my command:

cat /home/ubuntu/test/copy.txt | awk 'NR==21{print ".host = "$line";"}1'

$line is basically an IP address which is retrieved from a text file. With the above command the output looks like

.host = ;

Any immediate help would be really appreciated.

Format of copy.txt

backend default {
#.host = value; need to be here
.port = "8080";
}

1 + 3

ubuntu

awk

shell-scripting

Romeo Ninov

11/11/23, 1:30 PM

do you want to get `line` variable from file or from other source?

Romeo Ninov

11/11/23, 1:32 PM

And what is the exact format of the `copy.txt` file?

serverstackqns

11/11/23, 1:48 PM

@RomeoNinov- please check my update. also, regarding line, I am already capturing it from a file using while loop.

Score:0

Server

Romeo Ninov

11/11/23, 1:52 PM

The variables in awk can be transferred from shell on this way:

awk -v variable=$line '.....

and used inside on this way:

awk -v line1=$line 'NR==21 {print ".host = "line1";"}1'

The variable should be set beforehand in bash so the things become:

line=192.168.0.10
awk -v line1=$line 'NR==21 {print ".host = "line1";"}1' /path/to/file ...

Also you do not need cat, just use this way:

awk '....' /home/ubuntu/test/copy.txt

To store the output in a file you should use something like:

awk '....' /home/ubuntu/test/copy.txt >/home/ubuntu/test/new_copy.txt

and the result will be stored in /home/ubuntu/test/new_copy.txt

+ 7

serverstackqns

11/11/23, 2:45 PM

It works, however the file doesnt seem to be saved. The reason is I am able to see the file with the update printed, but checking the file in another window, there's no content in line 21. Any idea why?

Romeo Ninov

11/11/23, 3:19 PM

Because `awk` only print the content. Let me add more explanations to the answer

serverstackqns

11/11/23, 4:02 PM

Thanks, it works, but in line1 should be updated with the value along with "" (double quotes) example: "192.168.0.10". Now it is coming as 192.168.10.0. How can I achieve that?

Romeo Ninov

11/11/23, 4:10 PM

@serverstackqns, before exec the `awk` you should run command like `line=192.168.0.10` and in `awk` variable `line1` will get this value

serverstackqns

11/11/23, 4:16 PM

If you don't mind, can you please update the answer with this too.

Romeo Ninov

11/11/23, 4:20 PM

@serverstackqns, done. Maybe you should spend some time to learn `bash` scripting

serverstackqns

11/11/23, 4:20 PM

Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/140551/discussion-between-serverstackqns-and-romeo-ninov).

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Variable in AWK

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.