Get times and cut with SOX

I have a little problem taking audio times from a simple text file and cutting and audio file with SoX.

I have a time list like:

And I need make the audio partition with Sox, as follows:

sox NAME.wav NEW_NAME.wav trim "$time" "$duration"

To do this I need the Initial time and the Duration. For the Duration variable I jump one line from the lecture and get the next value amb make a substraction:

cat FILE.txt | while read line; 
do
end_time=`grep -A 1 $line FILE.txt | sed 1d`
start_time=$line
if [ -z "$end_time" ];
then
    end_time='21.853'
fi
#echo "This is start: $start_time"
#echo "This is end: $end_time"

duration=$(echo "$end_time-$start_time" | bc) 
#echo "DURATION: $duration"
done

But I get some errors in the Duration variable, can anyone help me with this script?

Thank you so much

Solution

Not sure if it fits your needs but it looks more logical to do it this way:

FILE.txt

0       4.053
8.879   15.651
19.684  21.853

yourscript.sh

cat FILE.txt | while read start_time end_time; 
do
    if [ -z "$end_time" ];
    then
        end_time='21.853'
    fi
    #echo "This is start: $start_time"
    #echo "This is end: $end_time"

    duration=$(echo "$end_time-$start_time" | bc) 
    echo "DURATION: $duration"
done

Output

DURATION: 4.053                                                                                                                                                          
DURATION: 6.772                                                                                                                                                          
DURATION: 2.169