在减去2猛砸变量 [英] Subtract 2 variables in Bash

问题描述

我有下面的脚本来减去2目录，但是 COUNT = 前pression不工作，什么是正确的语法？<之间的文件数/ p>

 ＃！的/ usr / bin中/ env的庆典
FIRSTV =`LS -1 | WC -l`
CD ..
SECONDV =`LS -1 | WC -l`
COUNT = EXPR $ FIRSTV- $ SECONDV
回声$ COUNT
 

解决方案

您只需要围绕减号一点点额外的空格和反引号：

  COUNT =`$ EXPR FIRSTV  -  $ SECONDV`
 

I have the script below to subtract the counts of files between 2 directories but the COUNT= expression does not work, what is the correct syntax?

#!/usr/bin/env bash
FIRSTV=`ls -1 | wc -l`
cd ..
SECONDV=`ls -1 | wc -l`
COUNT=expr $FIRSTV-$SECONDV
echo $COUNT

解决方案

You just need a little extra whitespace around the minus sign, and backticks:

COUNT=`expr $FIRSTV - $SECONDV`

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