mjhjmtu

I want to print matching strings in File1 using fields of File2 (standard file). I have tried below awk command and but only first line results are being printed, instead I would like to get all fields matching from File1 strings.

 cat File1
 AAA,20190221,00-00,100
 AAA,20190221,01-00,110
 AAA,20190221,02-00,120
 BBB,20190221,00-00,110
 BBB,20190221,01-00,110
 BBB,20190221,02-00,110
 CCC,20190221,00-00,110
 CCC,20190221,01-00,140
 CCC,20190221,02-00,150

 cat File2
 AAA
 BBB

I am using below awk method,

 awk -F"," -f vlookup.awk File1 File2
 (cat vlookup.awk)
 FNR==NR
 a[$1]=$4
 next
 if ($1 in a) print $1"," a[$1] else print $1, "NA" 

I am getting output as

 AAA,100
 BBB,110
 NA

but I need to print all the values from File1, that may increase or decrease time to time.
my expected output is

AAA,100
AAA,110
AAA,120
BBB,110
BBB,110
BBB,110

Your AWK script saves from File1 the last value from column 4 for every key from column 1 into array a using column 1 as index. Then it prints all array keys and values that are present in File2.

You should change the order of the input files and create an array of keys from File2, then compare the lines from File1 with this array.

vlookup2.awk

FNR==NR 
 a[$0]=1 # Set a value in array a using current line as index
 next # Stop processing this line, do not check other rules

$1 in a # if column1 matches any index in array a
 print $1 "," $4 # the columns you want

Run

awk -F "," -f vlookup2.awk File2 File1

to get

AAA,100
AAA,110
AAA,120
BBB,110
BBB,110
BBB,110

Note: I used File2 as the first argument.

BTW: There seems to be something wrong with your AWK script, your sample files and the output. I get two lines

AAA,120
BBB,110

which are the last lines from File1 with the corresponding key in column 1. Your example output shows the first line for AAA.

I get a line

 NA

(with a space before NA) only if File2 contains an empty line after BBB.