可以直接透過 ruby 來執行 commands 的指令。

• Kernel#`, commonly called backticks

Returns the result of the shell command.

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value = `echo 'hi'`
value = `#{cmd}`
value.class
#=> String 回傳結果

• %x(cmd)

跟上面的 ` 是類似

Returns the result of the shell command, just like the backticks. 會以字串形式回傳結果

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value = %x(echo 'hi')
value = %x[ #{cmd} ]

• Kernel#system

指令執行結果成功與否，回傳的是布林值

Return: true if the command was found and ran successfully, false otherwise

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wasGood = system("echo 'hi'")
wasGood = system(cmd)
wasGood.class
=> TrueClass 回傳有沒有成功

• Kernel#exec

會中斷當前的 process

Return: none, the current process is replaced and never continues

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exec("echo 'hi'")
exec(cmd) # Note: this will never be reached because of the line above

官方文件：

• Kernel
• Open3 - 可執行精密的操作

參考文件：

• Input & output in Ruby
• Calling shell commands from Ruby
• 6 Ways to Run Shell Commands in Ruby Tuesday
• Ruby#open 知多少？
• , Difference between exec, system and %x() or Backticks