执行命令并在 if 语句中进行比较 [英] Execute command and compare it in a if statement

问题描述

我正在使用 bash 脚本来检查两个特定目录是否包含特定数量的文件.让我们假设 20.是否可以在 if 语句中的一行中检查它?

I am using bash scripting to check whether two specific directories are containing some specific number of files. lets assume 20. Is it possible to check it in a line inside a if statement?

#!/bin/bash

if [ [ls /path/to/dir1 | wc -l ] != 20 ||  [ ls /path/to/dir2 | wc -l ] != 50 ]; then
  echo "do this!"
elif
  echo "do that!"
fi

推荐答案

语法错误:

if [[ $(ls /path/to/dir1 | wc -l)  != 20 || $(ls /path/to/dir2 | wc -l) != 50 ]] 
then
    echo "do this!"
else
    echo "do that!"
fi

(为了便于阅读，我移动了 then 的位置)

(I move the position of the then for readability)

使用两个方括号 [[ 可以使用 || 表示或"而不是 -o，这更接近于传统语言.严格来说，[[ 进行模式匹配，所以虽然上面的代码可以工作，但算术测试应该真正使用 ((:

With two square brackets [[ you can use || for "or" instead of -o, which is closer to conventional languages. Strictly speaking the [[ does pattern matching, so although the code above will work, an arithmetic test should really use ((:

if (( $(ls /path/to/dir1 | wc -l)  != 20 || $(ls /path/to/dir2 | wc -l) != 50 ))
then
    echo "do this!"
else
    echo "do that!"
fi

$() 运行一个子shell 并捕获输出.

The $( ) runs a subshell and captures the output.

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