Compare two files and matched line send to new file

Question

I have two files

file1.txt

a|1|cd a|2|cd a|4|cd

file2.txt

a|0001|hj|df a|0002|ed|nb a|0003|vf|za a|0004|er|ns a|0005|oi|lk

I need a create new file with the lines matched by de second column of the files, I try by then next code

awk -F"|" 'NR==FNR{a[$2]++;next} a[$2] ' file1.txt file2.txt

but no found records, because file1.txt in second column doesn't contain 0 at the left I have the instruction

awk -F"|" 'NR==FNR{a[$(printf("%09d\n", $2))]++;next} a[$2]'

but doesn't work.

The result must be:

file3.txt

a|0001|hj|df a|0002|ed|nb a|0004|er|ns

John1024 · Accepted Answer · 2015-10-28 23:46:48Z

Adding zero to field forces awk to treat it as a number, not a string:

$ awk -F"|" 'NR==FNR{a[$2+0]++;next} a[$2+0] ' file1.txt file2.txt a|0001|hj|df a|0002|ed|nb a|0004|er|ns

As a string 0001 is different from 1. By adding zero to each, we convert them to numbers which results in the comparison that you want.

@MiguelAngel $2+0 forces awk to treat $2 as a number, not a string. The ++ part of this command is separate and unrelated. — John1024
– John1024, Commented Oct 28, 2015 at 23:51

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