Linux join Command: Merge Files by Common Field

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

The frequently used options are:

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

Example:

Suppose that file1 contains the following content:

1 GZH-12342 HYD-23893 GIS-2348

And file2 has the following content:

1 Fiat Uno Mille Smart2 Audi A33 Monza

After the command:

$ join –j 1 arquivo1 arquivo2

The output will be as follows:

1 GZH-134 Fiat Uni Mille Smart2 HYD-2389 Audi A33 GIS-2348 Monza

TABLE - Symbols to differentiate header and footer

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

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

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