Question

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