bash 如何比较bash/awk中的两个十进制数？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/11237794/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to compare two decimal numbers in bash/awk?
提问by Paused until further notice.
I am trying to compare two decimal values but I am getting errors. I used
我正在尝试比较两个十进制值，但出现错误。我用了
if [ "$(echo $result1 '>' $result2 | bc -l)" -eq 1 ];then
as suggested by the other Stack Overflow thread.
正如其他 Stack Overflow 线程所建议的那样。
I am getting errors.
我收到错误。
What is the correct way to go about this?
解决这个问题的正确方法是什么？
回答by Paused until further notice.
You can do it using Bash's numeric context:
您可以使用 Bash 的数字上下文来做到这一点：
if (( $(echo "$result1 > $result2" | bc -l) )); then
bcwill output 0 or 1 and the (( ))will interpret them as false or true respectively.
bc将输出 0 或 1，(( ))并将它们分别解释为 false 或 true。
The same thing using AWK:
同样的事情使用 AWK：
if (( $(echo "$result1 $result2" | awk '{print ( > )}') )); then
回答by Steven Penny
if awk 'BEGIN{exit ARGV[1]>ARGV[2]}' "$z" "$y"
then
echo z not greater than y
else
echo z greater than y
fi
回答by Samir
Following up on Dennis's reply:
跟进丹尼斯的回复：
Although his reply is correct for decimal points, bash throws (standard_in) 1: syntax errorwith floating point arithmetic.
尽管他的回答对小数点是正确的，但 bash 抛出(standard_in) 1: syntax errorwith floating point algorithm。
result1=12
result2=1.27554e-05
if (( $(echo "$result1 > $result2" | bc -l) )); then
echo "r1 > r2"
else
echo "r1 < r2"
fi
This returns incorrect output with a warning although with an exit code of 0.
尽管退出代码为 0，但这会返回错误的输出并带有警告。
(standard_in) 1: syntax error
r1 < r2
(standard_in) 1: 语法错误
r1 < r2
While there is no clear solution to this (discussion thread 1and thread 2), I used following partial fix by rounding off floating point results using awkfollowed by use of bccommand as in Dennis's reply and this thread
虽然对此没有明确的解决方案（讨论线程 1和线程 2），但我使用了以下部分修复方法，通过在丹尼斯的回复和此线程中使用awk后跟使用bc命令来舍入浮点结果
Round off to a desired decimal place: Following will get recursive directory space in TB with rounding off at the second decimal place.
四舍五入到所需的小数位：以下将获得以 TB 为单位的递归目录空间，并在小数点后第二位四舍五入。
result2=$(du -s "/home/foo/videos" | tail -n1 | awk '{=/(1024^3); printf "%.2f", ;}')
You can then use bash arithmetic as above or using [[ ]]enclosure as in following thread.
然后，您可以使用上面的 bash 算法或使用如下线程中的[[ ]]外壳。
if (( $(echo "$result1 > $result2" | bc -l) )); then
echo "r1 > r2"
else
echo "r1 < r2"
fi
or using -eqoperator where bcoutput of 1 is trueand 0 is false
或使用-eq运算符，其中bc1 的输出为真，0 为假
if [[ $(bc <<< "$result1 < $result2") -eq 1 ]]; then
echo "r1 < r2"
else
echo "r1 > r2"
fi
回答by Timor Kodal
if [[ `echo "$result1 $result2" | awk '{print ( > )}'` == 1 ]]; then
echo "$result1 is greater than $result2"
fi
回答by progz
You can also echoan if...elsestatement to bc.
您还可以echo在if...else来声明bc。
- echo $result1 '>' $result2
+ echo "if (${result1} > ${result2}) 1 else 0"
(
#export IFS=2 # example why quoting is important
result1="2.3"
result2="1.7"
if [ "$(echo $result1 '>' $result2 | bc -l)" -eq 1 ]; then echo yes; else echo no;fi
if [ "$(echo "if (${result1} > ${result2}) 1 else 0" | bc -l)" -eq 1 ];then echo yes; else echo no; fi
if echo $result1 $result2 | awk '{exit !( > )}'; then echo yes; else echo no; fi
)
回答by Bernie Bored
Can't bash force type conversion? For example:
不能 bash 强制类型转换吗？例如：
($result1 + 0) < ($result2 + 0)
回答by Pierre Prot
Why use bc ?
为什么使用 bc ？
for i in $(seq -3 0.5 4) ; do echo $i ; if [[ (( "$i" < 2 )) ]] ; then echo "... is < 2";fi; done
The only problem : the comparison "<" doesn't work with negative numbers : they are taken as their absolute value.
唯一的问题：比较“<”不适用于负数：它们被视为它们的绝对值。
