How to export table data to file

When logged into psql:

COPY tablename TO 'filename';

For more details, see this: http://www.postgresql.org/docs/current/static/sql-copy.html

In psql:

\copy tablename to 'filename' csv;

First, log into the PostgreSQL console via the command line with the psql command.

To export:

\connect database_name;
\copy my_table TO 'my_table.csv' CSV;
\q

To import:

\connect database_name;
\copy my_table FROM 'my_table.csv' DELIMITER ',' CSV;
\q

Done!

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Or, from a shell script!

export PGPASSWORD=dbpass
psql --dbname=mydb --username=dbuser --host=127.0.0.1 -c "COPY (SELECT * FROM widget) TO stdout DELIMITER ',' CSV HEADER" > export.csv

Bonus Advice Use pgcli, it's way better than psql