Bash script with psql command tells nothing, but doesn't work

Question

I am really confused with this piece of code:

...
COM="psql -d $DBNAME -p $PGPORT -c 'COPY (SELECT * FROM $TABLE_NAME s WHERE cast(s.$COLUMN_NAME as DATE) < DATE '$DATE_STOP' ) TO '$SCRIPTPATH/$ARCHIVE_NAME--$DBNAME' WITH CSV HEADER;'"

su postgres -c '$COM' &> pg_a.log
...

in psql shell this SQL code works fine, but in script he is not creating archive and tells me nothing about mistakes or fails.

Thanks in advance!

Answer 1

You'll get one hint if you replace your "su" command with this:

echo '$COM'

What you'll see is that it prints out $COM -- not an expansion, but the string itself.

You'll probably find a number of other problems with this approach. You're going to have to escape a bunch of characters so the shell doesn't interpret them for you. It's going to be a real pain.

I would put the sql into a file and use the -f option to psql.