join omitting output lines when input sorted numerically

Question

i have two files, aa and bb:

 $ cat aa 
84 xxx
85 xxx
10101 sdf
10301 23

 $ cat bb
82 asd
83 asf
84 asdfasdf
10101 22232
10301 llll

i use the join command to join them:

 $ join aa bb
84 xxx asdfasdf

but what expected is 84, 10101 and 10301 all joined. Why only 84 has been joined?

Answer 1

Use a lexicographical sort rather than a numeric sort.

To do this as part of the process:

$ join <(sort aa) <(sort bb)

This gives the output:

10101 sdf 22232
10301 23 llll
84 xxx asdfasdf

Answer 2

You failed to include the fact that an error message is output:

$ join aa bb
join: file 2 is not in sorted order
84 xxx asdfasdf
join: file 1 is not in sorted order

You can use a normal lexicographic sort:

join <(sort aa) <(sort bb) | sort -k1,1n

Answer 3

If you want to avoid sorting, then you can zero pad with awk:

join \
 <(awk '{printf("%05d %s\n", $1, $2)}' aa) \
 <(awk '{printf("%05d %s\n", $1, $2)}' bb) \
| awk '{print int($1),$2,$3}'

Generates this output that preserves the original sort order:

84 xxx asdfasdf
10101 sdf 22232
10301 23 llll

You want to avoid sort, because Unix sort is O(n log n).