pg_config isn't installed by default on many systems, and is usually
part of postgresql-libs-devel or some such, leading to needless
"pg_config not found" errors on completion.
The ~/.psqlrc may alter the output. In particular, I have '\timing on'
in there to add timings. This is useful when using psql, but not when
relying on it in scripts.
For example:
psql -Aqt -c "select n.nspname \
from pg_catalog.pg_namespace n \
where n.nspname "'!~'" '^pg_' \
and n.nspname <> 'information_schema' \
order by 1;" postgres 2>/dev/null
Gives the output:
public
Time: 1.882 ms
Whereas with -X it gives the standard output:
public
Martin Tournoij