用于检查数字是否为 Armstrong 的 BASH 脚本
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BASH Script to Check if a number is Armstrong or Not
提问by Atif Mohammed Ameenuddin
I was writing a script to check if a number is Armstrong or not. This is my Code
我正在写一个脚本来检查一个数字是否是阿姆斯特朗。这是我的代码
echo "Enter Number"
read num
sum=0
item=$num
while [ $item -ne 0 ]
do
rem='expr $item % 10'
cube='expr $rem \* $rem \* $rem'
sum='expr $sum + $cube'
item='expr $item / 10'
done
if [ $sum -eq $num ]
then
echo "$num is an Amstrong Number"
else
echo "$num is not an Amstrong Number"
fi
After I run this script,
在我运行这个脚本之后，
$ ./arm.sh
$ ./arm.sh
I always get these errors
我总是收到这些错误
line 5: [: too many arguments
第 5 行：[: 参数太多
line 12: [: too many arguments
第 12 行：[：参数太多
I am on cygwin.
我在 cygwin 上。
回答by Kilian Foth
Those are straight quotes in your exprcommands. To evaluate an expression, you need to use backquotes:
这些是您的expr命令中的直引号。要评估表达式，您需要使用反引号：
rem=`expr $item % 10`
回答by Mark Edgar
The errors are from missing quotes in the [ ] command: [ "$item" -ne 0 ]. However, do not use [ ] for arithmetic expressions. Instead, use (( )):
错误来自 [ ] 命令中缺少引号： [ "$item" -ne 0 ]。但是，不要将 [ ] 用于算术表达式。相反，使用 (( ))：
while ((item != 0)); do ... done
而（（项目！= 0））；做...完成
Also, your calculation for Armstrong number seems to be wrong. Why are you cubing? You need to check that num has exactly three digits in that case, do you not? http://en.wikipedia.org/wiki/Narcissistic_number
此外，您对阿姆斯特朗数的计算似乎是错误的。你为什么要立方？在这种情况下，您需要检查 num 是否正好是三位数字，不是吗？ http://en.wikipedia.org/wiki/Narcissistic_number
Assuming you really meant the standard definition of "Armstrong number", this should work:
假设你真的指的是“阿姆斯壮数”的标准定义，这应该有效：
#!/bin/sh -eu
is_armstrong() {
local num digits sum
num=""
case "$num" in
# Reject invalid numerals.
(*[^0-9]*|0?*) echo "$num: invalid numeral." >&2; return 1;;
esac
digits=${#num}
sum=0
while ((num > 0)); do
((sum += (num % 10) ** digits))
((num /= 10))
done
((sum == ))
}
# Prompt the user for a number if none were give on the command line.
if (($# == 0)); then
read -p "Enter a natural number: " num
set -- "$num"
fi
# Process all the numbers.
for num in "$@"; do
num=$((num + 0)) # canonicalize the numeric representation
if is_armstrong "$num"; then
echo "$num is an Amstrong Number"
else
echo "$num is not an Amstrong Number"
fi
done
