如何编写一个bash脚本，在每天的某个时间请求权限后删除系统日志文件？

Question

我想写一个bash脚本，每天在东部标准时间晚上9点删除我的系统日志。

我的经验相对较少。

#!/bin/sh
# I would want it to self-execute at some time every day.
# Would that mean that the shell needs to always run in the background?
# Is there a method by which I can add this execution to a daemon or other 
# background-process's code-content? (If so please give me details)

touch /Permission.txt            

#^^Process creates a file in root directory

chflags nouchg /Permission.txt

#^^Just in case the "no changes" flag is on, preventing me from changing 
#  permissions

chmod 0747 /Permission.txt 

#^^Sets permissions so that I can write to the file without being root.
#  I also set group permissions to read-only, my logic being that I want
#  raw data to go into this file without it being modified by shared  
#  Ownership processes..? 

echo "Delete System Logs for: "%d"/"%m"/"%y" ?">/Permission.txt
open /Permission.txt
Input=/Permission.txt</dev/f0

#^^Not just for the purposes of this script but for future scripts-I want
#  to capture raw binary data from peripheral devices. Is the output
#  of the keyboard interpreted by the OS or any other process before saving
#  to the text file?
#  How do I get raw binary-output to a file from hardware devices? How can
#  I go about understanding the opcode syntax-whether it uses even or odd
#  parity; whether it is big or small endian; and other binary nuances. 

while [ $Input != "Exit" ]
 do
  read /Permission.txt
   if [ $Input == "Yes"|"yes" ]; then
    echo "Exit">/Permission.txt
     echo "sudo rm -rf /private/var/log/* ;">ttys000     #See 1 below
      echo "********"                                  #The Password
       fi
   if [ $Input == "No"|"no" ]; then
    echo "Exit">/Permission.txt
     fi
end
#  1 not sure where the process is in the system and whether or not sending 
#  that string to tty will result in the command being executed as if terminal
#  were running, will the ";" be seen as the return button being pressed?

我想让它监听模式"Yes“或"No”或它的二进制等价物。"read“命令在while循环中是如何工作的？如何确保它读取特定的模式？在进入"Exit“从而关闭while循环后，for循环是否正常工作，IE，关闭子进程内的父进程是否会立即中断子进程？

Answer 1

#!/bin/sh
# I would want it to self-execute at some time every day.
# Would that mean that the shell needs to always run in the background?

如果你考虑到在前台运行的含义，你就会理解为什么它需要在后台运行。如果您没有在那个确切的时间登录怎么办？如果您正在键入文档，该怎么办？您可能会考虑创建一个弹出窗口(Windows风格)，但是在哪里呢？哪个控制台？

# Is there a method by which I can add this execution to a daemon or other 
# background-process's code-content? (If so please give me details)

试试man crontab。在crontab中，您可以指定作业必须运行的频率(例如：

#  m    h  D   M  dow  cmd
   0    3  *   *   *   /usr/local/bin/backup.diaadm 

在我的系统上，每晚3:00运行我的备份-管理。

touch /Permission.txt

在根目录中创建这样的文件不是一个好主意。它可能应该在/var/local下的某个目录中。

# Process creates a file in root directory
chmod 0747 /Permission.txt 
# Sets permissions so that I can write to the file without being root.
# I also set group permissions to read-only, my logic being that I want direct
# and raw data to go into this file without it being modified by shared  
# Ownership processes..? 

747是一个奇怪的权限。如果您在多用户系统上，它应该(可能)是0774，并且您将管理员放在正确的组中。

我不明白你那有缺陷的逻辑。您不希望通过共享访问来修改数据，但您却将写权限授予了世界(=系统中的每个人)？

echo "Delete System Logs for: "%d"/"%m"/"%y" ?">/Permission.txt
open /Permission.txt
Input=/Permission.txt</dev/f0

我不确定您在这里试图建立的是什么。它不是有效的bash脚本。

# Not just for the purposes of this script but for future scripts-I want to be
# able to capture raw binary data from peripheral devices. Is the output
# of the keyboard interpreted by the OS or any other process before saving
# to the text file?
# How do I get raw binary-output to a file from hardware devices? How can
# I go about understanding the opcode syntax-whether it uses even or odd
# parity; whether it is big or small endian; and other binary nuances. 

通常，Unix下的外围设备由/dev下的设备文件表示。您应该能够执行cat /dev/devicename来读取来自设备的输入。但是，如果您想使用来自设备的原始输入，bash可能不是合适的工具。Perl和Python对这类事情有更好的支持，而C或C++最适合这类工作。

while read Input ; do

   if [ $Input == "Yes"|"yes" ]; then
      echo "Exit">/Permission.txt

在这里，您将覆盖正在读取的文件。我不明白为什么，这似乎是如此不合逻辑，以至于我怀疑你是否想要这样。

     echo "sudo rm -rf /private/var/log/*"
     echo "********"                                  #The Password

在脚本中使用sudo不是一个好主意。您应该确保脚本在正确的权限下运行。回显密码不是一个好主意。如果必须，您可以设置无密码的sudo vis visudo。

   fi

如果$Input == "No"|"no“；则echo "Exit">/Permission.txt

请看我之前对此的评论。

 fi

结束

结束？

#  1 not sure where the process is in the system and whether or not sending 
#  that string to tty will result in the command being executed as if terminal
#  were running, will the ";" be seen as the return button being pressed?

不是的。为什么会这样呢？回声到tty回声到tty。

你可能正在尝试这样的东西：

while read Input ; do
 if [ $Input = "Yes" ]; then
    sudo rm -rf /private/var/log/* ;
 elif [ $Input = "No" ]; then
    exit
 fi
done < /Permission.txt

你也应该，至少让你的代码通过shellcheck。