How can I pass variable to "awk" and use print ?

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08-11-2011

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How can I pass variable to "awk" and use print ?

Problem comes with following command:

Code:

[saturn@localhost Desktop]$ a=2
[saturn@localhost Desktop]$ awk  'NR==2 {print $2}' about.txt 
rights
[saturn@localhost Desktop]$ awk  "NR==2 {print $2}" about.txt 
All rights reserved. Use is subject to license terms.           ????why print all fields????
[saturn@localhost Desktop]$ awk  "NR==$a {print $2}" about.txt 
All rights reserved. Use is subject to license terms.           ????why print all fields????
[saturn@localhost Desktop]$ awk  'NR==$a {print $2}' about.txt 
                                                               !!!print nothing!!!

Why does it print all fields? How to resolve it.
Thanks!!

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08-11-2011

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Quote:

Code:

awk  "NR==2 {print $2}" about.txt

The awk script is specified between ", so the shell makes the substition for $2 before awk execution.

aigles

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08-11-2011

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Thanks!
However I want to use $a, not "2", I want to use variable set by others in the awk.

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Code:

awk -v a=$a 'NR==$a {print $2}' about.txt
awk 'NR==$a {print $2}' a=$a about.txt

aigles

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08-11-2011

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Thanks, your command seems get nothing:

Code:

[saturn@localhost Desktop]$ echo $a
2
[saturn@localhost Desktop]$ awk 'NR==$a {print $2}' a=$a about.txt
[saturn@localhost Desktop]$ awk -v a=$a 'NR==$a {print $2}' about.txt
[saturn@localhost Desktop]$

What's wrong?

915086731

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08-11-2011

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Oups !

Code:

awk -v a=$a 'NR==a {print $2}' about.txt
awk 'NR==a {print $2}' a=$a about.txt

Jean-Pierre.

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Thanks all !!

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