from shell prompt:

strace program_to_log | grep function_name_syslog_gets_placed_before > file_on_network_location_accessible_to_slack_workspace

alternative one liner:

strace program_to_log | grep function_name_syslog_gets_placed_before > data_log; mail -s 'await thing.sendLog('Here', payload)' slack@user.space data_log