Join problem: throwing error, join extra operand

Question

I want to join 3 files on a column which has sorted unique numeric values (those files have only one column of values though) and starts with same prefix for an example "usi".

Now, while I am doing this

join -j 1 ../Test_Data/usi* > ../Test_Data/join_output.txt

I am finding following error:

join: extra operand `usi_rtree_lw_100000.txt'
Try `join --help' for more information.

Any ideas?

Answer 1

join accepts only 2 files to join. To operate on 3 file you have to use 2 join calls:

join -j 1 <(join -j 1 ../Test_Data/usi-1 ../Test_Data/usi-2) ../Test_Data/usi-3 > ../Test_Data/join_output.txt

The above command requires bash, as uses process substitution. If you use another shell, please specify which.

Update according to the comment.
If you know only a file name pattern instead of exact file names, let the shell expand the pattern, capture the expanded list in an array then use the array elements as parameters:

file=(../Test_Data/usi*)
join -j 1 <(join -j 1 "${file[0]}" "${file[1]}") "${file[2]}"