WAL Archiving and base backup

Hello all,

I've been upgrading some of our PostgreSQL instances from 9.x to 12.x 
and we're using a master/slave setup based on continuous archiving.

I can read on 
https://www.postgresql.org/docs/12/continuous-archiving.html 25.3.3.2. 
Making an Exclusive Low-Level Backup that the exclusive method is 
deprecated.

But then this leads me to the following problem:

- Non-Exclusive Low-Level Backup requires that the functions 
pg_start_backup() and pg_stop_backup() be called in the *same* 
connection to the database

- we use scripts to automate the creation of the backup and it's 
deployment on the slave, after a server maintenance for example

- the example given in 25.3.6.1. Standalone Hot Backups still uses the 
exclusive (deprecated) method

So I have this question, how to script the making of base backup for 
transfer on the slave server when the two SQL functions must be called 
in the same connection, in Bash for example; is this doable?

Thanks for any pointers.

Regards
--
Issa