Rjoin

A tool for joining CSV data on command line.

Dual-licensed under MIT or unlicense

Add this to your Cargo.toml:

toml [dependencies] rjoin = "0.1.0"

add this to your crate root:

rust extern crate rjoin;

The binary name for rjoin is rj.

bash $ cargo install rjoin

(don't forget to add $HOME/.cargo/bin to your path).

it can perform the join on multiple fields
it has higher flexibilty on specifying the field separators and record terminators compared to GNU join
it has a very flexible CSV parser which can recognize quotes, escape characters and even comments (currently based on BurntSushi's excellent CSV library)
it is likely faster than GNU join when checking the correct order of records
it has (subjectively) cleaner CLI.

you need a specific output format. GNU join is more flexible on this, but it can be mitigated by piping the output to cut or awk.
you need a case insensitive join. This can be mitigated by preprocessing data with tr utility.
you need to perform the join as fast as possible by not checking the correct order of the input.

Let's suppose we have the following data:

bash $ cat left color,blue color,green color,red shape,circle shape,square

bash $ cat right altitude,low altitude,high color,orange color,purple To get the lines with the common key:

bash $ rj left right color,blue,orange color,blue,purple color,green,orange color,green,purple color,red,orange color,red,purple

Some comments:

by default, the first field is the key. If you wish to use another field, you can specify it using --key/-k option (even per file). rjoin supports multiple fields as the key, but the number of key fields in both files must be equal.
by default, only the lines with the common key are printed. If you wish to print also unmached lines from the left or right file, use any combination of these: --show-left/-l, --show-right/-r or --show-both/-b. Note however, if you use any of these options, the default behavior of showing matches of both files is reset and must be made explicit if desired by adding -b.
there are multiple lines with the same key in both files, resulting in Cartesian product.

To get the lines with the unmatched key in both files:

bash $ rj -lr left right altitude,low altitude,high shape,circle shape,square

Any kind of contribution (e.g. comment, suggestion, question, bug report and pull request) is welcome.

A big thanks to BurntSushi for his excellent work.