Is it possible to reference an environmental variable within a postgres sql command?

Question

For example, say I wanted to import a CSV file from a path on the same machine the postgres server is running on.

There is an environmental variable MyPath set on the system to '/path/to/my/csv/file/'.

I could easily import this CSV file as follow:

COPY MyTable FROM
'/path/to/my/csv/file/myTable.csv'
DELIMITERS ','
CSV HEADER;

Is it possible to reference the MyPath variable from within this postgres sql command? Something along the following lines:

COPY MyTable FROM
get_environmental_variable('MyPath') || 'myTable.csv'
DELIMITERS ','
CSV HEADER;

Answer 1

Try this while starting

 psql --set 'var=foo' -c '\i thesqlscript' 

And this in the query

update table set column = :var; 

This is taken from this question on the forum

If you are using an older version of postgres, this looks like the same question asked in the postgres forum (though this is many years ago). There is no direct way, but they have given a couple of workarounds.