Home Operation and Maintenance Linux Operation and Maintenance There are several types of Linux commands

There are several types of Linux commands

Feb 08, 2023 am 11:26 AM
linux

Linux commands have two types: 1. Internal commands (shell commands), which are recognized by the shell program and run inside the shell program; they are transferred into the memory when the system starts and are resident in the memory. So the execution efficiency is high. 2. External commands (file system commands) are programs outside of the bash shell and are software functions of the system. They are read from the hard disk into the memory when the user needs them.

There are several types of Linux commands

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

Two types of Linux commands

Linux commands are divided into internal commands (built-in commands) and external commands, internal commands and external commands The command functions are basically the same, but there are some subtle differences.

The built-in commands are transferred into the memory when the system starts. They are resident in the memory, so the execution efficiency is high. The external command is a software function of the system, which is read into the memory from the hard disk when the user needs it.

External commands

External commands are also called file system commands. They are programs outside the bash shell and are not part of the shell. External commands are typically located in /bin, /usr/bin, /sbin, or /usr/sbin. External commands are the utility part of the Linux system. Because the functions of utility programs are usually relatively powerful, the amount of programs they contain will also be large. When the system is loaded, they are not loaded into the memory together with the system, but when needed. Only then will it be called into memory.

Usually the entity of the external command is not included in the shell, but its command execution process is controlled by the shell program. The shell program manages the path search, loading and storage of external command execution, and controls the execution of commands. External commands are installed additionally outside of bash, usually placed in /bin, /usr/bin, /sbin, /usr/sbin... etc. You can use the "echo

$PATH" command to view the storage path of external commands, such as: ls, vi, etc.

Built-in commands

The internal commands are actually part of the shell program, which contain some relatively simple Linux system commands, which are recognized by the shell program and executed in the shell program. The shell program completes the operation internally. Usually when the Linux system is loaded and run, the shell is loaded and resides in the system memory.

Internal commands are written in the bash source code, and their execution speed is faster than external commands, because parsing the internal command shell does not require the creation of a child process. For example: exit, history, cd, echo, etc.

Explanation

The pwd command is a special command with two versions, one is a built-in command and the other is an external command.

Summary

External commands will create a child process containing a new environment, but built-in commands will not. In comparison, external commands are more expensive to use, so built-in commands are more efficient and will not be affected by environmental changes.

Distinguish between built-in commands and external commands

Syntax

type command

Case

We use the type command to check whether the cd command is an internal command or an external command. The specific command is as follows:

type cd

After running, the terminal output is as follows:

There are several types of Linux commands

We see that the output cd is a built-in command. Now, we use the type command again to check whether the ps command is a built-in command or an external command. The specific command is as follows:

type ps

After running, The terminal output is as follows:

There are several types of Linux commands

#We see that the position of the ps command is output, that is, it indicates that the ps command is an external command.

Related recommendations: "Linux Video Tutorial"

The above is the detailed content of There are several types of Linux commands. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undress AI Tool

Undress AI Tool

Undress images for free

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

PHP Tutorial
1488
72
How to adjust mysql into Chinese interface? Easy to set the Chinese language environment of mysql How to adjust mysql into Chinese interface? Easy to set the Chinese language environment of mysql Jun 04, 2025 pm 06:36 PM

To tune MySQL into a Chinese interface, it can be implemented through MySQLWorkbench or command line tools. 1) In MySQLWorkbench, open "Preferences", select the "Appearance" tab, and then select "Chinese(Simplified)" in the "Language" drop-down menu, and restart. 2) When using command line tools, set the operating system locale variables, such as using "exportLANG=zh_CN.UTF-8" on Linux or macOS, and then run the mysql client.

How does resource usage (CPU, memory) differ between Linux and Windows? How does resource usage (CPU, memory) differ between Linux and Windows? Jun 05, 2025 am 12:13 AM

Linux and Windows have their own advantages and disadvantages in CPU and memory usage: 1) Linux uses time slice-based scheduling algorithms to ensure fairness and efficiency; Windows uses priority scheduling, which may cause low-priority processes to wait. 2) Linux manages memory through paging and switching mechanisms to reduce fragmentation; Windows tends to pre-allocate and dynamic adjustment, and efficiency may fluctuate.

How does the cost of ownership differ between Linux and Windows? How does the cost of ownership differ between Linux and Windows? Jun 09, 2025 am 12:17 AM

Linux's cost of ownership is usually lower than Windows. 1) Linux does not require license fees, saving a lot of costs, while Windows requires purchasing a license. 2) Linux has low hardware requirements and can extend the service life of the device. 3) The Linux community provides free support to reduce maintenance costs. 4) Linux is highly secure and reduces productivity losses. 5) The Linux learning curve is steep, but Windows is easier to use. The choice should be based on specific needs and budget.

How does the performance of I/O operations differ between Linux and Windows? How does the performance of I/O operations differ between Linux and Windows? Jun 07, 2025 am 12:06 AM

LinuxoftenoutperformsWindowsinI/Operformanceduetoitscustomizablekernelandfilesystems,whileWindowsoffersmoreuniformperformanceacrosshardware.1)LinuxexcelswithcustomizableI/OschedulerslikeCFQandDeadline,enhancingperformanceinhigh-throughputapplications

How to install Linux alongside Windows (dual boot)? How to install Linux alongside Windows (dual boot)? Jun 18, 2025 am 12:19 AM

The key to installing dual systems in Linux and Windows is partitioning and boot settings. 1. Preparation includes backing up data and compressing existing partitions to make space; 2. Use Ventoy or Rufus to make Linux boot USB disk, recommend Ubuntu; 3. Select "Coexist with other systems" or manually partition during installation (/at least 20GB, /home remaining space, swap optional); 4. Check the installation of third-party drivers to avoid hardware problems; 5. If you do not enter the Grub boot menu after installation, you can use boot-repair to repair the boot or adjust the BIOS startup sequence. As long as the steps are clear and the operation is done properly, the whole process is not complicated.

How to enable the EPEL (Extra Packages for Enterprise Linux) repository? How to enable the EPEL (Extra Packages for Enterprise Linux) repository? Jun 17, 2025 am 09:15 AM

The key to enabling EPEL repository is to select the correct installation method according to the system version. First, confirm the system type and version, and use the command cat/etc/os-release to obtain information; second, enable EPEL through dnfinstallepel-release on CentOS/RockyLinux, and the 8 and 9 version commands are the same; third, you need to manually download the corresponding version of the .repo file and install it on RHEL; fourth, you can re-import the GPG key when encountering problems. Note that the old version may not be supported, and you can also consider enabling epel-next to obtain the test package. After completing the above steps, use dnfrepolist to verify that the EPEL repository is successfully added.

How does Linux perform compared to Windows for web server workloads? How does Linux perform compared to Windows for web server workloads? Jun 08, 2025 am 12:18 AM

Linux usually performs better in web server performance, mainly due to its advantages in kernel optimization, resource management and open source ecosystem. 1) After years of optimization of the Linux kernel, mechanisms such as epoll and kqueue make it more efficient in handling high concurrent requests. 2) Linux provides fine-grained resource management tools such as cgroups. 3) The open source community continuously optimizes Linux performance, and many high-performance web servers such as Nginx are developed on Linux. By contrast, Windows performs well when handling ASP.NET applications and provides better development tools and commercial support.

How to choose a Linux distro for a beginner? How to choose a Linux distro for a beginner? Jun 19, 2025 am 12:09 AM

Newbie users should first clarify their usage requirements when choosing a Linux distribution. 1. Choose Ubuntu or LinuxMint for daily use; programming and development are suitable for Manjaro or Fedora; use Lubuntu and other lightweight systems for old devices; recommend CentOSStream or Debian to learn the underlying principles. 2. Stability is preferred for UbuntuLTS or Debian; you can choose Arch or Manjaro to pursue new features. 3. In terms of community support, Ubuntu and LinuxMint are rich in resources, and Arch documents are technically oriented. 4. In terms of installation difficulty, Ubuntu and LinuxMint are relatively simple, and Arch is suitable for those with basic needs. It is recommended to try it first and then decide.

See all articles