awk/gawk array concatenation into string fail - awk

Question

I want to concatenate a array into a string in gawk
have the array a [ ABC, DEF, GHI ]
and want a string like "ABC DEF GHI"
here I simplified the pipe feeding with 'echo' for demonstration purpouses:
test... working OK (no concatenation, only output)
#(echo ABC & echo DEF & echo GHI) | gawk '{a[$0]++} END { for( f in a ) print f; }'
now try to concatenate
#(echo ABC & echo DEF & echo GHI) | gawk '{a[$0]++} END { for( f in a ) b=(b f); print b; }'
just returns the 1st string in the array 'a'...
?any ideas on how to do this...

Answer 1

If you're trying to print the concatenated values of a Unix shell array such as created by:
$ a=(ABC DEF GHI)
then just do:
$ echo "${a[*]}"
ABC DEF GHI
If you want to concatenate multiple input lines as produced by:
$ printf '%s\n' "${a[#]}"
ABC
DEF
GHI
with awk for some reason then there's several options including:
$ printf '%s\n' "${a[#]}" | awk '{printf "%s%s", (NR>1 ? OFS : ""), $0} END{print ""}'
ABC DEF GHI
$ printf '%s\n' "${a[#]}" | awk '{b=(NR>1 ? b OFS : "") $0} END{print b}'
ABC DEF GHI
$ printf '%s\n' "${a[#]}" | awk '{a[NR]=$0} END{for (i=1; i<=NR; i++) b=(i>1 ? b OFS : "") a[i]; print b}'
ABC DEF GHI
$ printf '%s\n' "${a[#]}" | awk '{a[NR]=$0} END{for (i=1; i<=NR; i++) printf "%s%s", (i>1 ? OFS : ""), a[i]; print ""}'
ABC DEF GHI
If none of that is what you're trying to do then please edit your question to clarify your requirements.