Join command in Linux (join files)

The join command in Linux (join) joins the lines of both files that have a common index. The join command can be used as a simple database.

The commonly used options are:

• -j1 number: Choose the number field as the index for file1.
• -j2 number: Choose the number field as the index for file2.
• -j number: Choose the number field as the index for both files.

Example:

Assume that file1 contains the following content:

1 GZH-1234 2 HYD-2389 3 GIS-2348

And file 2 has the following content:

1 Fiat Uno Mille Smart 2 Audi A3 3 Monza

After the command:

$ join —j 1 file1 file2

The output will be as follows:

1 GZH-134 Fiat Uni Mille Smart 2 HYD-2389 Audi A3 3 GIS-2348 Monza

TABLE - Symbols to differentiate header and footer

Symbol	Description
:::	Symbol used to start the text header
::	Symbol used to start the text body
:	Symbol used to start the text footer

Note that the join command requires that both files contain an index, as in the example.

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