combine 2 files with AWK based last colums [closed] - awk

Question

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Closed 10 years ago.
i have two files
file1
-------------------------------
1 a t p b
2 b c f a
3 d y u b
2 b c f a
2 u g t c
2 b j h c
file2
--------------------------------
1 a b
2 p c
3 n a
4 4 a
i want combine these 2 files based last columns (column 5 of file1 and column 3 of file2) using awk
result
----------------------------------------------
1 a t p 1 a b
2 b c f 3 n a
2 b c f 4 4 a
3 d y u 1 a b
2 b c f 3 n a
2 b c f 4 4 a
2 u g t 2 p c
2 b j h 2 p c

Answer 1

at the very beginning, I didn't see the duplicated "a" in file2, I thought it would be solved with normal array matching. ... now it works.
an awk onliner:
awk 'NR==FNR{a[$3"_"NR]=$0;next;}{for(x in a){if(x~"^"$5) print $1,$2,$3,$4,a[x];}}' f2.txt f1.txt
test
kent$ head *.txt
==> f1.txt <==
1 a t p b
2 b c f a
3 d y u b
2 b c f a
2 u g t c
2 b j h c
==> f2.txt <==
1 a b
2 p c
3 n a
4 4 a
kent$ awk 'NR==FNR{a[$3"_"NR]=$0;next;}{for(x in a){if(x~"^"$5) print $1,$2,$3,$4,a[x];}}' f2.txt f1.txt
1 a t p 1 a b
2 b c f 3 n a
2 b c f 4 4 a
3 d y u 1 a b
2 b c f 3 n a
2 b c f 4 4 a
2 u g t 2 p c
2 b j h 2 p c
note, the output format was not sexy, but it would be acceptable if pipe it to column -t

Answer 2

Other way assuming files have no headers:
awk '
FNR == NR {
f2[ $NF ] = f2[ $NF ] ? f2[ $NF ] SUBSEP $0 : $0;
next;
}
FNR < NR {
if ( $NF in f2 ) {
split( f2[ $NF ], a, SUBSEP );
len = length( a );
for ( i = 1; i <= len; i++ ) {
$NF = a[ i ];
}
}
printf "%s\n", $0;
}
' file2 file1 | column -t
It yields:
1 a t p 1 a b
2 b c f 3 n a
2 b c f 4 4 a
3 d y u 1 a b
2 b c f 3 n a
2 b c f 4 4 a
2 u g t 2 p c
2 b j h 2 p c

Answer 3

A bit easier in a language that supports arbitrary data structures (list of lists). Here's ruby
# read "file2" and group by the last field
file2 = File .foreach('file2') .map(&:split) .group_by {|fields| fields[-1]}
# process file1
File .foreach('file1') .map(&:split) .each do |fields|
file2[fields[-1]] .each do |fields2|
puts (fields[0..-2] + fields2).join(" ")
end
end
outputs
1 a t p 1 a b
2 b c f 3 n a
2 b c f 4 4 a
3 d y u 1 a b
2 b c f 3 n a
2 b c f 4 4 a
2 u g t 2 p c
2 b j h 2 p c