can not use unix $variable in awk command [duplicate] - linux

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Using awk with variables
(3 answers)
Closed 8 years ago.
I have following variable set in my unix environment. If i try to use it in awk command its not working but the same command is working when i dont use $b variable
$b="NEW"
when i try following command it is not working
echo "$a" | tr [a-z] [A-Z] |awk -v RS=, '/TABLE/&&/CREATE/&&/`echo ${b}`/{print $NF}'
But, if i replace the $b value to NEW as below its working
echo "$a" | tr [a-z] [A-Z] |awk -v RS=, '/TABLE/&&/CREATE/&&/NEW/{print $NF}'

Answer 1

You cannot use a bash var inside awk like that. Instead, use:
echo "$a" | tr [a-z] [A-Z] | awk -v RS=, -v myvar=$b '/TABLE/&&/CREATE/&& $0~myvar {print $NF}'
See an example:
$ var="hello"
$ awk -v text=$var 'BEGIN{print text}'
hello
Also, to me it works with tr 'a-z' 'A-Z' instead of tr [a-z] [A-Z]. And based on Mark Setchell suggestion, you can skip it by using the IGNORECASE = 1:
echo "$a" | awk -v RS=, -v myvar=$b 'BEGIN{IGNORECASE=1} /TABLE/&&/CREATE/&& $0~myvar {print $NF}'

Answer 2

Regarding your question:
if i replace the $b value to NEW as below its working
It works because the value of your variable is NEW and what you end up doing is using that in the regex, which is exactly how it is supposed to be done.
about your second question:
can not use unix $variable in awk command
You cannot use shell variables in awk like that. You need to create an awk variable by using -v option and assigning your bash variable.
awk -v awkvar="$bashvar" '/ /{ ... }'
This makes your existing syntax as:
echo "$a" | tr [a-z] [A-Z] | awk -v RS=, -v var="$b" '/TABLE/&&/CREATE/&&/var/{print $NF}'
This again won't work because inside /../ variables are not interpolated, meaning they are considered literally. So, you need to do:
echo "$a" | tr [a-z] [A-Z] |awk -v RS=, -v var="$b" '/TABLE/&&/CREATE/&&$0~var{print $NF}'