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This article introduces the relevant knowledge of "what is the meaning of the process in linux". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

A process is an instance of a program running in Linux and the basic unit for managing transactions; the process has its own independent processing environment and system resources. The state of a process changes, including its creation, scheduling, and demise.

The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

A process is an instance of a program running in Linux.

In the Linux system, the operating system completes a task through the process, and the process is the basic unit of managing transactions. The process has its own independent processing environment (such as which environment variables are currently needed, where the program is running, which user is currently running the program, etc.) and system resources (such as processor CPU occupancy, memory, Imax O devices, data, programs).

When you execute a program in a Linux system, the system creates a specific environment for the program. This environment contains everything the system needs to run the program.

Every time you execute a command in Linux, it creates or starts a new process. For example, when you try to run the command "ls-l" to list the contents of the directory, you start a process. If two terminal windows are displayed on the screen, you may have run the same terminal program twice, and there will be two terminal processes.

Each terminal window may have a Shell running, and each running Shell is a process. When you call a command from Shell, the corresponding program will be executed in a new process, and when the process of the program is finished, the process of Shell will resume running.

The operating system tracks the process through a digital code called PID or process ID. Each process in the system has a unique PID.

Now let's look at the processes in Linux through an example. We execute the following command from the Shell command line:

$sleep 10 & [1] 3324

Because the program waits for 10 seconds, we quickly look for any process named sleep on the current Shell:

$ps-ef | grep sleepmozhiyan 3324 5712 cons1 17:11:46 / usr/bin/sleep

We see that the process named / usr/bin/sleep is running on the system (its PID is the same as the PID we got in the previous command).

Now let's try to run the above sleep command in parallel from three different terminal windows, and the output of the above command will look similar to the following:

$ps-ef | grep sleepmozhiyan 896 5712 cons1 17:16:51 / usr/bin/sleepmozhiyan 5924 5712 cons1 17:16:52 / usr/bin/sleepmozhiyan 2424 5712 cons1 17:16:50 / usr/bin/sleep

We see that each instance of the sleep program creates a separate process.

Each Linux process has another ID number, the ID (ppid) of the parent process. Every user process in the system has a parent process.

The command "ps-f" lists the PID and PPID of the process. The output of this command is similar to the following:

$ps-f UID PID PPID TTY STIME COMMANDmozhiyan 4124 228 cons0 21:37:09 / usr/bin/psmozhiyan 228 1 cons0 21:32:23 / usr/bin/bash

All commands you run from the Shell command line prompt have the current Shell process as the parent process. For example, if you type the ls command at the Shell command line prompt, Shell will execute the ls command, and the Linux kernel will copy the memory page of Shell, and then execute the ls command.

In Unix, each process is created using the fork and exec methods. However, this method will lead to the loss of system resources.

In Linux, the fork method is implemented using copy memory pages on write, so it only results in the loss of time and memory required to copy the memory page table of the parent process, and creates a unique task structure for the child process.

The copy-on-write mode avoids creating unnecessary structural copies when creating new processes. For example, if the user outputs the ls command at the Shell command line prompt, the Linux kernel will create a child process of Shell, that is, the process of the Shell is the parent process, while the process of the ls command is the child process, the process of the ls command points to the same memory page as this Shell, and the child process executes the ls command using write-time copy-time technology.

Status of the process

Each Linux process has its own life cycle, such as creation, execution, termination, and cleanup. Each process also has its own state, showing what is currently happening in the process. The state of a process changes, including its creation, scheduling, and demise.

A process can have the following states:

D (uninterruptible hibernation)-the process is dormant and cannot be recovered until an event occurs.

R (running status)-the process is running.

S (dormant state)-the process is not running, but is waiting for an event or signal.

T (stop state)-the process is stopped by a signal, such as signal SIGINT or SIGSTOP.

Z (zombie)-the processes marked are zombie, and they remain because their parent process destroys them properly. If the parent process exits, they will be destroyed by the init process.

To view the status of a specified process, use the following command:

Ps-C processName-o pid=,cmd,stat

For example:

This is the end of $ps-C sleep-o pid=,cmd,stat CMD STAT9434 sleep 20 S "what is the meaning of process in linux". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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