Why does awk seem to randomize the array?

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If you look at output of this awk test, you see that array in awk seems to be printed at some random pattern. It seems to be in same order for same number of input. Why does it do so?

echo "one two three four five six" | awk '{for (i=1;i<=NF;i++) a[i]=$i} END {for (j in a) print j,a[j]}'
4 four
5 five
6 six
1 one
2 two
3 three


echo "P04637 1A1U 1AIE 1C26 1DT7 1GZH 1H26 1HS5 1JSP 1KZY 1MA3 1OLG 1OLH 1PES 1PET 1SAE 1SAF 1SAK 1SAL 1TSR 1TUP 1UOL 1XQH 1YC5 1YCQ" | awk '{for (i=1;i<=NF;i++) a[i]=$i} END {for (j in a) print j,a[j]}'
17 1SAF
4 1C26
18 1SAK
5 1DT7
19 1SAL
6 1GZH
7 1H26
8 1HS5
9 1JSP
10 1KZY
20 1TSR
11 1MA3
21 1TUP
12 1OLG
22 1UOL
13 1OLH
23 1XQH
14 1PES
1 P04637
24 1YC5
15 1PET
2 1A1U
25 1YCQ
16 1SAE
3 1AIE

Why does it do so, is there rule for this?

awk arrays
4 Answers

If you are using gawk or mawk, you can also set an env variable WHINY_USERS, which will sort indices before iterating.

Example:

echo "one two three four five six" | WHINY_USERS=true awk '{for (i=1;i<=NF;i++) a[i]=$i} END {for (j in a) print j,a[j]}'
1 one
2 two
3 three
4 four
5 five
6 six

From mawk's manual:

WHINY_USERS

This is an undocumented gawk feature. It tells mawk to sort array indices before it starts to iterate over the elements of an array.

user_10805230
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