UNIX Command Line

$ cat main.txt
ID1:A:45
ID2:B:12
ID4:C:12
ID3:D:56
ID7:F:90
ID9:K:14
ID5:P:32

$ cat filter.txt
ID7:0
ID3:0
ID4:0

Required output: Delete those lines from "main.txt" for which the ID field (first field) matched with that in "filter.txt". Basically the output file say rest.txt will be subtraction of filter.txt from main.txt.

The awk solution:

$ awk >rest.txt 'NR==FNR{arr[$1];next}!($1 in arr)' FS=":" filter.txt main.txt

or

$ awk >rest.txt 'NR==FNR{_[$1];next}!($1 in _)' FS=":" filter.txt main.txt

Result:

$ cat rest.txt
ID1:A:45
ID2:B:12
ID9:K:14
ID5:P:32