How to check if a postgresql backup is finished or not?
You can use the function pg_is_in_backup() in PostgreSQL >= 9.3, see Backup Control Functions

For example:

SELECT pg_is_in_backup();


If the result is false, then the computer is not currently backing up. But this depends on the kind of backup you're doing (i.e. via PgAdminIII, SQL command, or pgdump).