關於while 和for循環的cpu性能以及內存佔用情況
同樣的腳本文件，分別使用for和while完成，再用top查看cpu和內存的情況。
[root@localhostfish]# cat sumwhile.sh
#!/bin/bash
#
declare-i sum=0
declare-i i=1
while [ $i -le 1000000 ];do
letsum+=$i
let i++
done
echo $sum
[root@localhostfish]# top -b -d 0.1 >>sum_while_top
[root@localhostfish]# grep 40392 sum_while_top
4039240279 root 20 0 103m 1196 1040 R 95.5 0.1 0:16.36 sumwhile.sh 內存佔用情況以及佔用cpu的時間
4039240279 root 20 0 103m 1196 1040 R 94.9 0.1 0:16.46 sumwhile.sh
4039240279 root 20 0 103m 1196 1040 R 100.0 0.1 0:16.58 sumwhile.sh
4039240279 root 20 0 103m 1196 1040 R 94.7 0.1 0:16.68 sumwhile.sh
0:00.64sumwhile.sh
[root@localhostfish]# cat sumfor.sh
#!/bin/bash
#
declare-i sum=0
for i in `seq 1 1000000`; do
letsum+=$i
done
echo $sum
top -b -d0.1 >> sum_for_top
[root@localhostfish]# grep 40485 sum_for_top
4048540279 root 20 0 201m 99m 1048 R 100.0 10.0 0:43.45 sumfor.sh
4048540279 root 20 0 201m 99m 1048 R 94.7 10.0 0:43.55 sumfor.sh
4048540279 root 20 0 201m 99m 1048 R 95.0 10.0 0:43.65 sumfor.sh
4048540279 root 20 0 201m 99m 1048 R 100.0 10.0 0:43.76 sumfor.sh
4048540279 root 20 0 201m 99m 1048 R 100.0 10.0 0:43.87 sumfor.sh
for循環對內存的佔用和對cpu的佔用都明顯高於while循環。
求解答原因。