https://www.jianshu.com/p/ea61be326568
test
判斷符號 []
[ -z "${HOME}" ] ; echo $?
必須要注意中括號的兩端需要有空白字符來分隔喔! 假設我空白鍵使用“□”符號來表示,那麼,在這些地方你都需要有空白鍵:
- 在中括號 [] 內的每個元件都需要有空白鍵來分隔;
- 在中括號內的變量,最好都以雙引號括號起來;
錯誤示範
name="shark ops"
[ ${name} == "xiguatian" ]
會報錯
bash: [: too many arguments
之前的是會這樣的
[ ${name} == "xiguatian" ]
會變成 [ shark ops == "xiguatian" ]
所以應該寫成下面這樣
[ "${name}" == "xiguatian" ]
會變成 [ "shark ops" == "xiguatian" ]