带有变量 bash 的降序循环
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descending loop with variable bash
提问by LanceBaynes
$ cat fromhere.sh
#!/bin/bash
FROMHERE=10
for i in $(seq $FROMHERE 1)
do
echo $i
done
$ sh fromhere.sh
$
Why doesn't it works?
I can't find any examples searching google for a descending loop..., not even variable in it. Why?
为什么它不起作用？
我找不到任何在谷歌搜索降序循环的例子......，甚至没有变量。为什么？
回答by Roy
You should specify the increment with seq:
您应该使用 seq 指定增量：
seq $FROMHERE -1 1
回答by Paused until further notice.
Bash has a forloop syntax for this purpose. It's not necessary to use the external sequtility.
for为此，Bash 有一个循环语法。没有必要使用外部seq实用程序。
#!/bin/bash
FROMHERE=10
for ((i=FROMHERE; i>=1; i--))
do
echo $i
done
回答by Shakiba Moshiri
loop down with for (stop play)
循环使用 for（停止播放）
for ((q=500;q>0;q--));do echo $q ---\>\ `date +%H:%M:%S`;sleep 1;done && pkill mplayer
500 ---> 18:04:02
499 ---> 18:04:03
498 ---> 18:04:04
497 ---> 18:04:05
496 ---> 18:04:06
495 ---> 18:04:07
...
...
...
5 ---> 18:12:20
4 ---> 18:12:21
3 ---> 18:12:22
2 ---> 18:12:23
1 ---> 18:12:24
pattern :
图案 ：
for (( ... )); do ... ; done
example
例子
for ((i=10;i>=0;i--)); do echo $i ; done
result
结果
10
9
8
7
6
5
4
3
2
1
0
with while: first step
使用while：第一步
AAA=10
then
然后
while ((AAA>=0));do echo $((AAA--));sleep 1;done
or: "AAA--" into while
或：“AAA--”进入while
while (( $((AAA-- >= 0)) ));do echo $AAA;sleep 1;done
"sleep 1" isn't need
不需要“睡眠 1”
回答by Jürgen H?tzel
You might prefer Bash builtinShell Arithmetic instead of spawning external seq:
您可能更喜欢 Bash内置Shell Arithmetic 而不是产生外部seq：
i=10
while (( i >= 1 )); do
echo $(( i-- ))
done
