"awk variables in regex expression ?"

Post #302486124 by michaelrozar17 on Friday 7th of January 2011 03:48:10 AM

Originally Posted by vilius

Could someone explain why this one returns nothing:
$ x=/jon/
$ echo jon | awk -v xa=$x '$1~xa {print}'

When a pattern matching is done using ~ we need to give the reg-exp in between / / (2 forward slashes).Still, when given inside the slashes it is taken as literally, so when changing the above awk as
echo jon | awk -v xa=$x '$1~/xa/ {print}'

it matches the word xa and not the variable xa's value.Hence we need to expand the variable as below
echo jon | awk -v xa=$x '$1~/'"$xa"'/ {print}'

This is not the case when == is used as you would know this is used to equate between variables.Therefore in code $1==xa.. xa is expanded (to jon).
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