VyOS supports executing configuration and operational commands non-interactively from shell scripts.
To include VyOS-specific functions and aliases you need to source /opt/vyatta/etc/functions/script-template files at the top of your script.
#!/bin/vbash source /opt/vyatta/etc/functions/script-template
Running configuration commands
Configuration commands are executed just like from a normal config session.
For example, if you want to disable a BGP peer on VRRP transition to backup:
#!/bin/vbash source /opt/vyatta/etc/functions/script-template configure set protocols bgp 65530 neighbor 192.0.2.1 shutdown commit
All of set, delete, edit, top, up, commit should work.
Running operational commands
Unlike a normal configuration sessions, all operational commands must be prepended with "run", even if you haven't created a session with configure.
#!/bin/vbash source /opt/vyatta/etc/functions/script-template run show interfaces