Bash 脚本算术语法错误
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Error in Bash script arithmetic syntax
提问by Humble Debugger
Script:
脚本：
#!/bin/bash
vpct=5.3
echo $((vpct*15))
Error:
错误：
./abc.sh: line 5: 5.3: syntax error: invalid arithmetic operator (error token is ".3")
I know I don't need a script to multiply 5.3 * 15, but this small script to single out the error. Please advise.
我知道我不需要一个脚本来乘5.3 * 15，但是这个小脚本来挑出错误。请指教。
采纳答案by kurumi
Besides bc, there are other tools you can tools you can try
此外bc，还有其他工具可以尝试
awk -v vpct="$VPCT" 'BEGIN{print vpct * 15}'
echo $vpct | ruby -e 'print gets.to_f * 15 '
echo "$vpct 15 * p" | dc
回答by SirDarius
According to http://www.softpanorama.org/Scripting/Shellorama/arithmetic_expressions.shtml:
根据http://www.softpanorama.org/Scripting/Shellorama/arithmetic_expressions.shtml：
Bash does not understand floating point arithmetic. It treats numbers containing a decimal point as strings.
Bash 不了解浮点运算。它将包含小数点的数字视为字符串。
You should use bc to perform such calculations, just as in dogbane's solution, except that you should escape the expression using quotes so the *character doesn't cause unwanted shell expansion.
您应该使用 bc 来执行此类计算，就像在 dogbane 的解决方案中一样，只是您应该使用引号对表达式进行转义，以便该*字符不会导致不需要的外壳扩展。
echo "$vpct*15" | bc
回答by dogbane
You should use bc for floating point arithmetic:
您应该使用 bc 进行浮点运算：
echo "$vpct*15" | bc
回答by Paused until further notice.
If you have ksh available, it will do float arithmetic.
如果您有可用的 ksh，它将执行浮点运算。
回答by Paused until further notice.
Shebang should be written like #!And anyway $(())is only for integers.
Shebang 应该写成#!And 无论如何$(())只适用于整数。
回答by Cedric
$(( $vpct * 15 )) // (add a $ sign should do it)
$(( $vpct * 15 )) // （添加一个 $ 符号应该这样做）
