对一个程序进行多次运行，求其平均运行时间

function timediff() 
{# time format:date +"%s.%N", such as 1502758855.907197692start_time=$1end_time=$2start_s=${start_time%.*}start_nanos=${start_time#*.}end_s=${end_time%.*}end_nanos=${end_time#*.}# end_nanos > start_nanos? # Another way, the time part may start with 0, which means# it will be regarded as oct format, use "10#" to ensure# calculateing with decimalif [ "$end_nanos" -lt "$start_nanos" ];thenend_s=$(( 10#$end_s - 1 ))end_nanos=$(( 10#$end_nanos + 10**9 ))fi# get timedifftime=$(( 10#$end_s - 10#$start_s )).$(( (10#$end_nanos - 10#$start_nanos)/10**6 ))avgtime=`echo "sclae=4; $time/$n" | bc -l`echo $avgtime
}starttime=`date +'%s.%N'`i=0
n=5
while [ $i -lt 5 ] #循环，把两个5改成想要运行的次数
do./a.out big quicksort1_opti2  #需要运行的程序waitlet i=i+1
done
wait # 等待执行完成 即可
endtime=`date +'%s.%N'`echo "程序平均运行时间： "  
timediff $starttime $endtime #比较开始和结束时间的差
echo " s"
exit 0

./running_time.sh >> result.txt

可以使结果写入文本中

nohup ./running_time.sh >> result.txt &

转入后台运行，终端可以继续干别的

jobs
命令查看后台程序

nohup python -u TargetRecongnizer-pt.py > out 2>&1 &

• -u 不缓存，实时输出到 out 文件
• >> 追加， > 覆盖