linux - awk error with "[" and "]" delimiters -

linux - awk error with "[" and "]" delimiters -

i have string looks likes this

string="xxxxx.yyyyy[2].zzzzz"

i want extract number between [ ]. used next awk command

echo $string | awk -f'[]' '{print $2}'

but awk command returns error:

awk: bad regex '[]': unmatched [ or [^

how prepare that?

this should work:

echo "xxxxx.yyyyy[2].zzzzz" | awk -f '[][]' '{print $2}' 2

order of ] before [ within character class of import here.

this shall work double escaping [ , ] using alternation regex:

echo "xxxxx.yyyyy[2].zzzzz" | awk -f '\\[|\\]' '{print $2}' 2

or:

echo "xxxxx.yyyyy[2].zzzzz" | awk -f '[\\[\\]]' '{print $2}' 2

linux shell awk ash