Apart from the usual Linux commands that display status, the Raspberry Pi includes a custom command named vcgencmd, which can report voltages and temperatures. This chapter documents the known features of the command.
The executable file behind the command is /usr/bin/vcgencmd.
There is no man page for this command, but the list of all supported options can be displayed with the commands option. The command output has been broken over several lines for readability:
$ vcgencmd commandscommands="vcos, ap_output_control, ap_output_post_processing, \pm_set_policy, pm_get_status, pm_show_stats, pm_start_logging, ...