你如何在 Bash 脚本中找到一个数字的阶乘？
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How do you find the factorial of a number in a Bash script?
提问by user409345
In shell scripting how to find factorial of a number?
在shell脚本中如何找到一个数字的阶乘？
回答by ghostdog74
seq -s "*" 1 500 |bc
回答by paxdiablo
You don'tdo it in bash. Intelligent people don't try to cut down trees with a fish, so my advice is to try and use the right tool for the job.
你不要在bash. 聪明的人不会试图用鱼砍树，所以我的建议是尝试使用正确的工具来完成这项工作。
You can use, for example, bcto do it thus:
例如，您可以使用以下bc方法执行此操作：
pax> echo 'define f(x) {if (x>1){return x*f(x-1)};return 1}
f(6)' | bc
720
pax> echo 'define f(x) {if (x>1){return x*f(x-1)};return 1}
f(500)' | BC_LINE_LENGTH=99999 bc
12201368259911100687012387854230469262535743428031928421924135883858
45373153881997605496447502203281863013616477148203584163378722078177
20048078520515932928547790757193933060377296085908627042917454788242
49127263443056701732707694610628023104526442188787894657547771498634
94367781037644274033827365397471386477878495438489595537537990423241
06127132698432774571554630997720278101456108118837370953101635632443
29870295638966289116589747695720879269288712817800702651745077684107
19624390394322536422605234945850129918571501248706961568141625359056
69342381300885624924689156412677565448188650659384795177536089400574
52389403357984763639449053130623237490664450488246650759467358620746
37925184200459369692981022263971952597190945217823331756934581508552
33282076282002340262690789834245171200620771464097945611612762914595
12372299133401695523638509428855920187274337951730145863575708283557
80158735432768888680120399882384702151467605445407663535984174430480
12893831389688163948746965881750450692636533817505547812864000000000
00000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000
回答by Vitalii Fedorenko
#!/bin/bash
counter= #first argument
factorial=1
while [ $counter -gt 0 ] #while counter > 0
do
factorial=$(( $factorial * $counter ))
counter=$(( $counter - 1 ))
done
echo $factorial
回答by nos
echo 500 | dc -e '?[q]sQ[d1=Qd1-lFx*]dsFxp'
回答by Nordic Mainframe
10! in bash:
10！在 bash 中：
f=1; for k in {1..10}; do f=$[$k * $f] ; done; echo $f
or here in a step by step fashion:
或者在这里一步一步地：
$ t=$(echo {1..10})
$ echo $t
1 2 3 4 5 6 7 8 9 10
$ t=${t// /*}
$ echo $t
1*2*3*4*5*6*7*8*9*10
$ echo $[$t]
3628800
回答by HuZaiFa ZahoOr
echo Enter Number
read num
fact=1
for ((i=1;i<=num;i++))
do
fact=$(($fact*$i))
done
echo $fact
回答by Paused until further notice.
Here is a recursive function in Bash:
这是 Bash 中的递归函数：
factorial () {
if (( == 1))
then
echo 1
return
else
echo $(( $( factorial $(( - 1)) ) * ))
fi
}
Of course it's quite slow and limited.
当然，它非常缓慢且有限。
回答by user456584
There are a number of instructive examples on Rosetta Code.
关于 Rosetta Code有许多有启发性的例子。
Here's one I found particularly useful:
这是我发现特别有用的一个：
function factorial {
typeset n=
(( n < 2 )) && echo 1 && return
echo $(( n * $(factorial $((n-1))) ))
}
回答by Milen John Thomas
Please use this script to find factorial in Bash,
请使用此脚本在 Bash 中查找阶乘，
#!/bin/bash
num=
fact=1
for((i=1; i<=$num; i++))
do
let fact=fact*i
done
echo "Factorial is $fact"
回答by insanikov
I almost completely agree with Vitalii Fedorenko, I would just like paxdiablo suggests use bc, here's the code from Vitalii Fedorenko but modified to use bc.
我几乎完全同意 Vitalii Fedorenko，我只是希望 paxdiablo 建议使用bc，这是来自 Vitalii Fedorenko 的代码，但修改为使用bc.
#!/bin/bash
counter=
output=1
while [ $counter -gt 1 ] #while counter > 1 (x*1=x)
do
output=$(echo "$output * $counter" | bc)
counter=$(($counter - 1))
done
#remove newlines and '\' from output
output=$(echo "$output" | tr -d '\' | tr -d '\n')
echo "$output"
exit
This method is better because bcallows you to use strings, instead of integers, making it possible for you to calculate much bigger numbers.
这种方法更好，因为bc允许您使用字符串而不是整数，使您可以计算更大的数字。
I apologize if I haven't used trcorrectly, I am not very familiar with it.
如果我没有tr正确使用，我很抱歉，我对它不是很熟悉。
