#! /bin/zsh

# use once:
#
#     a-level t
#
# continous: invoke with signal USR1;
#            terminate with C-c C-c
#
#     a-level
#     kill -s USR1 PID

# should be faster than 300 ms
do-a-level () {
    (($#)) || (($+AUDIO_OUTPUT)) || set /dev/stdout
    rec --null stat trim 0 0.1 2>&1 | \
        grep 'Maximum amplitude'    | \
        cut -d' ' -f 7 >> $1
}

trap 'do-a-level' USR1

(($+1)) && do-a-level || while ((1)) {}