进程调度-优先级

pr 进程优先级
ni nice值越小，优先级越高

1. 实验：

   $nice = $argv[1];
   $count = 0;
   $start = time();
   $pid = pcntl_fork();
   
   if ($pid == 0){
       // 设置
       fprintf(STDOUT, "child process pid=%d, nice=%d\n", posix_getpid(), pcntl_getpriority(posix_getpid()));
       pcntl_setpriority($nice, posix_getpid(), PRIO_PROCESS);
       fprintf(STDOUT, "child process pid=%d, nice=%d\n", posix_getpid(), pcntl_getpriority(posix_getpid()));
       while (1){
           $count++;
           if (time() - $start > 5){
               break;
           }
       }
   }elseif ($pid > 0){
       fprintf(STDOUT, "parent process pid=%d, nice=%d\n", posix_getpid(), posix_getsid(posix_getpid()));
       while (1){
           $count++;
           if (time() - $start > 5){
               break;
           }
       }
   }
   
   fprintf(STDOUT, "proc:%d count:%d \n", posix_getpid(), $count);
   sleep(2);
   

2. 测试
   • php demo4.php 5
   • php demo4.php 20
   • php demo4.php -10

suid特权进程

进程运行过程种需要特殊的权限，临时赋值

1. suid，sgid给程序文件，程序文件启动后就是一个特权进程
2. 这样无权限用户可以通过特权程序完成特殊操作。
3. 特权进程也可在有需求时获取对应权限进行操作。特殊标识是s

实验：

// chmod 4755 /usr/bin/php
// su other 
// php demo6.php

$file="aaa.txt";

$uid = posix_getuid();
$euid = posix_geteuid();
fprintf(STDOUT, "uid=%d, euid=%d \n", $uid, $euid);

posix_seteuid($euid);
posix_setuid($euid);

$uid = posix_getuid();
$euid = posix_geteuid();
fprintf(STDOUT, "uid=%d, euid=%d \n", $uid, $euid);

if (posix_access($file, POSIX_W_OK)){
    fprintf(STDOUT, "I can change file\n");
}else{
    fprintf(STDOUT, "I can't change file\n");
}