Question

我有这个用bash编写的脚本

#!/bin/sh

# script makes grep directly on dmesg output
# looking  for  'USB disconnect'  phrase  if
# it  finds  it  then  machine  is  rebooted
# ver 1.2
clear

UNPLUG_MESSAGE="PLEASE UNPLUG THE USB STICK NOW"
echo $UNPLUG_MESSAGE && sleep 2

while true; do

USB_STATUS=`dmesg | tail -n 5 |  grep 'disconnect'`

  if [[ $USB_STATUS == *USB?disconnect* ]]
     then
        clear && echo "Rebooting... bye" 
    sleep 1 && sudo reboot

  elif [[ $USB_STATUS != *USB?disconnect* ]]
     then
        clear && echo "Please remove USB drive..."
        sleep 2
  fi
done

exit 0

将＃！/ bin / bash更改为＃！/ bin / sh后，脚本不再起作用了 - 我应该在此脚本中更改什么内容？

我得到的错误就像未知的操作数 USB？disconnect ,. / renboot.sh：16：./ renboot.sh：[[：not found，etc。

Answer 1

在ubuntu上sh是dash（您可以ls -l $(which sh)运行以查看此内容。）

在dash中，没有[[（双括号）运算符。您必须仅使用test内置函数或[（单括号）。

您可以替换：

if [[ $USB_STATUS == *USB?disconnect* ]]
...
elif [[ $USB_STATUS != *USB?disconnect* ]]

人：

if [ $(echo $USB_STATUS | grep -c "USB disconnect") != 0 ]
...
elif [ $(echo $USB_STATUS | grep -c "USB disconnect") = 0 ]

bash sh差异，脚本转换

1 个答案: