bash中与变量的浮点比较 [英] Floating point comparison with variable in bash

问题描述

我想将一个浮点变量与一个整数进行比较.我知道这对 bash 来说不是最好的，但是我的整个脚本已经用 bash 编写了.$number 可以是任何整数.如果它低于或等于 50，我想要 output1，对于所有其他人，我想要一个带有其他变量 k 的输出.这是我目前所拥有的:

I want to compare a floating point variable to an integer. I know this is not the best to do with bash, but my whole script is already written in bash. $number can be any integer. If it below or equal 50, I want output1, for all others I want an output with the other variable k. This is what I have so far:

number=43
test=$(echo "scale=2; $number/50" | bc -l)
echo "$test"
for k in {1..5}
do
    if ["$test" -le 1]
    then echo "output"

    elif ["$test" -gt $k]
    then echo "output$k"
    fi
done

如果我尝试使用 test=0.43，第一个循环甚至不起作用.我认为它与整数和浮点比较有关，但无法使其工作.

If I try with test=0.43, the first loop does not even work. I think it has to do with an integer and a floating point comparison but cannot make it work.

有什么我遗漏的吗?

PS:这个[0.43: command not found是终端输出的.

PS:this [0.43: command not found is what the terminal outputs.

推荐答案

Bash 无法处理浮点数.改为管道到 bc:

Bash can't handle floats. Pipe to bc instead:

if [ $(echo " $test > $k" | bc) -eq 1 ]

您看到的错误是因为 test 命令(即 [)前后需要空格

The error you see though is because the test command (i.e. the [) needs spaces before and after

使用 (( ... )) 会更好，因为您可以这样比较数字:

It is even better to use (( ... )) since you compare numbers like this:

if (( $(bc <<< "$test > $k") ))

循环中的部分应该是这样的:

The part in the loop should look like this:

if (( $(bc <<< "$test <= 1") ))
then
    echo "output"
elif (( $(bc <<< "$test > $k") ))
then
    echo "output$k"
fi

关系表达式的值为 0，如果关系为假，则为 1，如果关系为真 [来源].但是请注意，这是 GNU bc 的一种行为，它不符合 POSIX.

Relational expressions evaluate to 0, if the relation is false, and 1 if the relation is true [source]. Note however that is a behavior of GNU bc, and it is not POSIX compiant.

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