sandhya mentioned :
=> No...What i need is...
=> I want to know the equivalent sql queries for \l and \dt commands in order
=> to list the databases and tables.
=> I want to do it through programming
From the psql man-page :
-E
--echo-hidden
Echoes the actual queries generated by \d and other backslash
commands. You can use this if you wish to include similar func-
tionality into your own programs. This is equivalent to setting
the variable ECHO_HIDDEN from within psql.
If this is not _exactly_ what you need, then you're not exactly
explaining what you're trying to do :)