Processing 2 files with different field separators using awk

Question

Let's say I have 2 files :

$ cat file1
A:10
B:5
C:12

$ cat file2
100 A
50 B
42 C

I'd like to have something like :

A 10 100
B 5 50
C 12 42

I tried this :

awk 'BEGIN{FS=":"}NR==FNR{a[$1]=$2;next}{FS=" ";print $2,a[$2],$1}' file1 file2

Which outputs me that :

  100 A
B 5 50
C 12 42

I guess the problem comes from the Field Separator which is set too late for the second file. How can I set different field separator for different files (and not for a single file) ?

Thanks

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Edit: a more general case

With file2 and file3 like this :

$ cat file3
A:10 foo
B:5 bar 
C:12 baz

How to get :

A 10 foo 100
B 5 bar 50
C 12 baz 42

Answer 1

Just set FS between files:

awk '...' FS=":" file1 FS=" " file2

i.e.:

$ awk 'NR==FNR{a[$1]=$2;next}{print $2,a[$2],$1}' FS=":" file1 FS=" " file2
A 10 100
B 5 50
C 12 42

Answer 2

You need to get awk to re-split $0 after you change FS.

You can do that with $0=$0 (for example).

So {FS=" ";$0=$0;...} in your final block will do what you want.

Though only doing that the first time you need to change FS will likely perform slightly better for large files.