Looping over input fields as array

Question

Is it possible to do something like this:

$ cat foo.txt
1 2 3 4
foo bar baz
hello world
$ awk '{ for(i in $){ print $[i]; } }' foo.txt
1
2
3
4
foo
bar
baz
hello
world

I know you could do this:

$ awk '{ split($0,array," "); for(i in array){ print array[i]; } }' foo.txt
2
3
4
1
bar
baz
foo
world
hello

But then the result is not in order.

Yes, associative arrays are unordered collections. – glenn jackman Aug 09 '11 at 14:16 — glenn jackman, Aug 09 '11 at 14:16

score 64 · Accepted Answer · answered Aug 09 '11 at 14:08

64

Found out myself:

$ awk '{ for(i = 1; i <= NF; i++) { print $i; } }' foo.txt

answered Aug 09 '11 at 14:08

Tyilo

Note you can delete the braces in `for` since you are executing just one command. – fedorqui Jun 13 '16 at 11:16

score 1 · Answer 2 · answered Sep 07 '17 at 14:59

1

No need for awk, sed or perl. You can easily do this directly in the shell:

for i in $(cat foo.txt); do echo "$i"; done

answered Sep 07 '17 at 14:59

Sven Marnach

score 1 · Answer 3 · edited Aug 09 '11 at 15:52

1

I'd use sed:

sed 's/\ /\n/g' foo.txt

edited Aug 09 '11 at 15:52

DisgruntledGoat

answered Aug 09 '11 at 14:09

dala

Doesn't work because I need to manipulate the seperated fields in awk. Or then I have to both involve sed and awk – Tyilo Aug 09 '11 at 14:44

Chris Koknat · Answer 4 · 2017-03-13T17:40:22.210

If you're open to using Perl, either of these should do the trick:

perl -lane 'print $_ for @F' foo.txt
perl -lane 'print join "\n",@F' foo.txt

These command-line options are used:

-n loop around each line of the input file, do not automatically print the line
-l removes newlines before processing, and adds them back in afterwards
-a autosplit mode – split input lines into the @F array. Defaults to splitting on whitespace.
-e execute the perl code

4 Answers4