如何在 perlscript 中在用户（包括 root）之间跳转？

Question

这个问题已在此处以多种形式提出。我再问一次，因为所有这些问题都有太多细节。因此，答案都归结为如何解决这些特定问题，而无需在用户之间跳转。
这就是我为什么将其作为一个新问题发布（并在下面立即回答），以供其他有此问题的人使用。

假设您有一个以 root 身份运行的 perl 脚本，您首先要以 root 身份运行，然后以普通用户身份运行，然后再次以 root 身份运行。

例如：

#!/usr/bin/perl
#Problem 1: Make sure to start as root
system("whoami");
#Problem 2: Become your regular user
system("whoami");
#Problem 3: Become root again
system("whoami);

应更改为显示：

root
your_username
root

Answer 1

这是我能想到的最好的解决方案。

如果您想以 root 身份启动，请成为普通用户并再次成为 root：

#!/usr/bin/perl
use POSIX qw/setuid waitpid/;
exec("sudo", $0, @ARGV) unless($< == 0);  #Restart the program as root if you are a regular user
system("whoami");
my $pid = fork;  #create a extra copy of the program
if($pid == 0) {
  #This block will contain code that should run as a regular user
  setuid(1000);  #So switch to that user (e.g. the one with UID 1000)
  system("whoami");
  exit;  #make sure the child stops running once the task for the regular user are done
}
#Everything after this will run in the parent where we are still root
waitpid($pid, 0); #wait until the code of the child has finished
system("whoami");

以普通用户身份开始时，最好确保父母保持普通用户身份，而孩子成为 root 用户。你可以这样做：

#!/usr/bin/perl
use POSIX qw/setuid waitpid/;
unless($< == 0) {
  #regular user code, this is the first code that will run
  system("whoami");
  #now fork, let the child become root and let the parent wait for the child
  my $pid = fork;
  exec("sudo", $0, @ARGV) if($pid == 0);
  waitpid($pid, 0);
  #continue with regular user code, this is the 3th part that will run
  system("whoami");
  exit; #the end of the program has been reached, exit or we would continue with code meant for root
}
#code for root, this is the 2nd part that will run
system("whoami");