How to concatenate psql variables?

Question

How can I concatenate two psql (PostgreSQL client) variables? I want to generate an absolute path by concatenating a directory path variable and a filename variable.

I've tried this:

\set path '/tmp/'
\set file 'foo'
\echo :path:file

But psql puts a space between the path and the file, and outputs:

/tmp/ foo

Answer 1

\set path '/tmp/'
\set file 'foo'
\set pf :path:file \echo :pf
/tmp/foo

Why does this work? I quote the manual here:

\set [ name [ value [ ... ] ] ]

Sets the internal variable name to value or, if more than one value is given, to the concatenation of all of them. [...]

Emphasis mine.

Answer 2

Try this:

\set path /tmp/
\set file foo
\qecho :path:file \o | sed s/\ //
/tmp/foo

\qecho writes to the query output channel (unlike \echo, which writes to standard output). \o | then redirects the output to the subsequent command.

Answer 3

It looks like you want either the || operator or the concat function:

http://www.postgresql.org/docs/9.1/static/functions-string.html