Shell Programming and Scripting

awk -F,                                                 # set input  field separator to ","
 -vOFS="|"                                              # set output field separator to "|"
'NR == FNR                                              # if processing first file (file line No. == stream line No.)
                {T[$1]                                  # save "remove location" as index in an (empty) array
                 next                                   # stop processing script for this line; start over with next line
                }
                                                        # now in second file
                {for (t in T)                           # loop through T's indices (awk feature)
                                gsub (t ",*|, *$", _)   # replace index string plus evtl. comma, or trailing comma with
                                                        # empty string (unassigned variable "_")
                 $1 = $1                                # Replace all comma field separators with "|". man awk:  "Assignment
                                                        # to NF or to a field causes $0 to be reconstructed by concatenating
                                                        # the $i's  separated  by  OFS."
                }
!seen[$0]++                                             # print first occurrences of lines only (remove duplicates) 
' file2 file1