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Insert external variable in a AWK pattern

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# 1  
Old 11-13-2009
CPU & Memory Insert external variable in a AWK pattern
Dear all,

¿How can i insert a variable in a AWK pattern?

I have almost succeeded in solving a puzzle with AWK but now i want to make a script. Let me explain.
Code:
cat file.txt | awk 'BEGIN {RS="\\n\\n"} /tux/  { print "\n"$0 }'

I know that this command makes right what i want to do, but mi intention is make a generic script whit a input parameter instead of 'tux' constant. Can you help me please?

Thanks
Last edited by radoulov; 11-13-2009 at 06:09 AM.. Reason: Added code tags.
# 2  
Old 11-13-2009
Something like this ?

Code:
awk -v var_name="value"  '##use the variable as you wish' input_filename.txt

# 3  
Old 11-13-2009
No way, if i put this in the command does not works, it only takes the variable in the print field.

Doesn't works:

Code:
cat file.txt  | awk -v var_name=$id 'BEGIN {RS="\\n\\n"} /var_name/  { print "\n"$0 }'

Works, but i dont want use the variable there

Code:
cat file.txt  | awk -v var_name=$id 'BEGIN {RS="\\n\\n"} /tux/  { print var_name "\n"$0 }'

Last edited by radoulov; 11-13-2009 at 06:08 AM.. Reason: Use code tags, please!
# 4  
Old 11-13-2009
You need:

Code:
$0 ~ var_name

not:

Code:
/var_name/


And in this case you don't need to call external commands like cat.
# 5  
Old 11-13-2009
Still not working...

Code:
cat file.txt | awk 'BEGIN {RS="\\n\\n"} $0 ~ '$id'  { print "\n"$0 }'

cat file.txt | awk 'BEGIN {RS="\\n\\n"} $0 ~ $id  { print "\n"$0 }'

cat file.txt | awk -v var_name=$id 'BEGIN {RS="\\n\\n"} $0 ~ var_name  { print "\n"$0 }'

Last edited by radoulov; 11-13-2009 at 06:24 AM.. Reason: added code tags
# 6  
Old 11-13-2009
Quote:
Originally Posted by antuan
Still not working...

cat file.txt | awk 'BEGIN {RS="\\n\\n"} $0 ~ '$id' { print "\n"$0 }'
[...]
I said:

Code:
$0 ~ var_name

not:

Code:
$0 ~ $var_name

And you need to set the variable for AWK as the previous poster pointed out:

Code:
% print -l a b | awk -vvar=a '$0 ~ var'
a
% print -l a b | awk '$0 ~ var' var=a
a


...

In your case it would be:

Code:
awk -vid=$id 'awk 'BEGIN {RS="\\n\\n"}  $0 ~ id  { print "\n" $0 }' file.txt

Or probably just:

Code:
awk '$0 ~ id' RS= id=$id file.txt

Last edited by radoulov; 11-13-2009 at 06:32 AM..
# 7  
Old 11-13-2009
i tested all cases.
note that $id is an external variable, and its what i want to put as AWK pattern.. Should I use the -v option ? Please complete my command, so I will understand you better. thanks
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