计算sql执行时间（结束时间-开始时间）

#!/bin/bash

function timediff() {
# time format:date +"%s.%N", such as 1502758855.907197692
    start_time=$1
    end_time=$2
   
    start_s=${start_time%.*}
    start_nanos=${start_time#*.}
    end_s=${end_time%.*}
    end_nanos=${end_time#*.}
   
    # end_nanos > start_nanos?
    # Another way, the time part may start with 0, which means
    # it will be regarded as oct format, use "10#" to ensure
    # calculateing with decimal
    if [ "$end_nanos" -lt "$start_nanos" ];then
        end_s=$(( 10#$end_s - 1 ))
        end_nanos=$(( 10#$end_nanos + 10**9 ))
    fi
    
    time=$(( 10#$end_s - 10#$start_s )).$(( (10#$end_nanos - 10#$start_nanos)/10**6 ))
    #return $time
    echo $time
}

for i in `seq 1 9`
do
    start=$(date +"%s.%N")
    psql < ./"10"$i".tpcds.0"$i".sql"
    end=$(date +"%s.%N")
    time=`timediff $start $end`
    echo "第"$i"个SQL   ""$time"
done

for i in `seq 110 199`
do
    start=$(date +"%s.%N")
    after=100
    num=$((i-after))
    psql < ./$i".tpcds."$num".sql"
    end=$(date +"%s.%N")
    time=`timediff $start $end`
    echo "第"$num"个SQL   ""$time"
done

#start=$(date +"%s.%N")
# Now exec some command
#end=$(date +"%s.%N")
# here give the values
# start=1502758855.907197692
# end=1502758865.066894173