![]() ![]() UID User ID PPID Parent process identifier. Here are some more parameters listed, adding onto the list above. This means that they have no controlling terminals. You'll notice that some processes have a TTY of ?. $ ps -ef UID PID PPID C STIME TTY TIME CMD The -e or -A options displays all processes (including daemon). The -f option prints full format listing, meaning it includes additional parameters. GNU long As you're most likely familiar with, any GNU long options are preceded by two dashes (-). ![]() Unix98 These options are preceded by one dash, and are probably what you're most familiar with. BSD These come from an earlier Berkeley Software Distribution platform and require no dashes at all. Depending on where these options originated, you may or may not need dashes preceding the option letter. Options with psĪs we'll see soon, the ps command comes with a variety of options. CMD The command that started the process. The higher it is, the more resources it's taking from the computer. TIME Amount of CPU time consumed by the process. X programs and daemons don't have this, but text-mode programs do (eg. Refers to the terminal that is controlling the process. $ psĪt the most basic level, there are only four columns. This only displays the processes that run from the current terminal, so are limited. We can easily view processes, using ps (process status). Now that we understand the concept of processes and learned a little bit of its jargon, let's see how we can view and control processes with shell commands. Orphan ProcessesĪn orphan process arises when a process is still running, but its parent has died. until the parent process fetches status info for terminated child, this process is known as a zombie. All memory and resources are released from the terminated child, and only its entry remains. Zombie processesĪ zombie (or defunct) process arise when a child process is terminated, but its entry still lives in the process table. Every process has a parent, except the init process. If a process is run through the command line interface, or shell, the shell is the parent. What results is a parent-child process relationship. Processes can launch other processes through appropriate system calls such as fork or spawn. Some example daemon processes are the mail and print daemons, which wait for some mail, or print job to come in. These processes just sit in the background and perform their tasks without any user interface. Most processes initialized by init are daemon programs (prounounced DEE-man). Here are a few types of processes you should familiarize yourself with. Since init is the first running process, it is given a PID of 1. With each consecutive process, a unique identifier is given. Upon boot, the very first process to be run is init (short for initialization).Īfter init is started, a series of shell scripts in /etc called init scripts are executed. In this section, we'll go over how to examine what processes are doing, and how to interact with processes to stop or pause them as needed. Time sharing system with multiple processes. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |