Open System Services Shell and Utilities Reference Manual (G06.29+, H06.08+, J06.03+)

User Commands (g - j) join(1)
3. To perform a join operation and display selected fields, enter:
join -o 2.3,2.1,1.2 phonedir names
This command displays the following fields in this order:
Field 3 of names (department number without "Dept.")
Field 1 of names (last name)
Field 2 of phonedir (telephone number)
If phonedir contains:
Binst 555-6235
Dickerson 555-1842
Eisner 555-1234
Green 555-2240
Hrarii 555-0256
Janatha 555-7358
Lewis 555-3237
Takata 555-5341
Wozni 555-1234
and names contains:
Eisner Dept. 389
Frost Dept. 217
Green Dept. 311
Takata Dept. 454
Wozni Dept. 520
then join -o 2.3,2.1,1.2 phonedir names displays:
389 Eisner 555-1234
311 Green 555-2240
454 Takata 555-5341
520 Wozni 555-1234
4. To perform a join operation on a field other than the first field, enter:
sort -b +1 -2 phonedir | join -1 2 - numbers
This command combines the lines in phonedir and names, comparing
the second field of phonedir to the first field of numbers.
First, this command sorts phonedir by the second field, because both
files must be sorted by the join field. The output of sort is then piped to
join. The - (dash) by itself causes the join command to use this sorted
output as its file1. -1 2 defines the second field of the sorted phonedir as
the join field. This field is compared to the first field of numbers (its
join field is not specified with a -2 flag).
If phonedir contains:
Binst 555-6235
Dickerson 555-1842
Eisner 555-1234
Green 555-2240
Hrarii 555-0256
Janatha 555-7358
Lewis 555-3237
527188-021 Hewlett-Packard Company 4−69