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Returns the number of microseconds since the Unix epoch (UTC of midnight January 1, 1970)

From the Dialplan

 <action application="set" data="rec_full=/var/spool/freeswitch/audio_rec/${strmicroepoch()}_${uuid}.wav"/>
 <action application="set" data="record_post_process_exec_app=system:/opt/scripts/proc_record ${rec_full}"/>
 <action application="record_session" data="${rec_full}"/>

From the CLI

strmicroepoch