How to use shell variable in awk?

Shell Programming and Scripting
1

How do you use a shell variable in awk? I am using Solaris 10 and don't have GNU products installed.

File (transportation.txt) contents:

car
boat 
airplane
snowmobile
bicycle
sled

This awk statment works (prints from the car line down to bicycle

awk '/car/,/bicycle/' transportation.txt

But what if instead of car I use a shell variable named vehicle (where the variable can be any value) passed by the user?

This line doesn't work (what's missing?)

awk '/$vehicle/,/bicycle/' transportation.txt
2

I have a blog on this
Chi Hung Chan: Four Ways to Pass Shell Variables in AWK

3

Thanks for the info. How do you apply the first way and second way to my awk command line. Sorry, I'm new to awk.

---------- Post updated at 09:19 PM ---------- Previous update was at 08:09 PM ----------

Will this work?

awk 'END{'/a/,/bicycle/}' a=$vechicle transportation.txt

thanks for the help.......

4 
vechicle="car"
awk '/'$vehicle'/,/bicycle/' transportation.txt

Since you are using '/.../' , second way cannot be used.

1 Like
5

Do I need the first line if $vechicle is defined elsewhere? $vehicle with be defined by the user and set in the script. set vechicle=$argv[1].

6

You should have nawk on a Solaris 10 box, so either of these should work and avoid any nasty quoting games:


awk 'match( $0, v ),/bicycle/' v="$vehicle" input-file

nawk -v v="$vehicle" 'match( $0, v ),/bicycle/' input-file

And, as long as vehicle is set before you use it, you should be fine.

1 Like
7

Agama, can you explain the lines of code? How does it know to stop searching at bicycle? Should the bar part of your code be bicycle?

8

Oops, I was testing with a file that had foo and bar, and didn't change it when I put it into the example.

Yes! It should be bicycle.

Sorry about that!

9 
awk '$0~t,/bicycle/' t="$vehicle" infile

On Solaris use /usr/xpg4/bin/awk

The first 3 examples will only work for variables without spaces or special characters, because there are no double quotes around them (this is not a variable assignment). It is perhaps also good to point out that the second example will not work in the BEGIN section.