Linux system performance analysis (top command) and more accurate interpretation of memory occupancy (free-m command)

I. System performance analysis (Top command)The top command is a common performance analysis tool under Linux that shows the resource usage of each process in real time, and refreshes the list of processes by default for 5 seconds, so it is similar

100 Common Linux Commands

1,echo "AA" > Test.txt and Echo "BB" >> test.txt//> Empty the original file, and the content is written to the file,>> put the content to the end of the file2,chmod go+w-r/home/zhangy//Add Write permission to group users and other users3,TAR-TZVF

The fork () function in Linux is detailed (original!!) examples) (reproduced)

First, Fork Introduction knowledgeA process, including code, data, and resources assigned to the process. The fork () function creates a process that is almost identical to the original process through a system call.That is, two processes can do

Linux multicast problem (No such device) workaround

The test code for multicasting is as follows:#include #include #include #include #include #include #include #include #include #include int main (int argc, char*argv[]) {int sockfd;//Socket file descriptor struct SOCKADDR_IN local_a Ddr

Compression decompression of Linux file management

The compressed format of files in Linux is *.gz/*.bz2/*.xz/*.zip/*. Z, respectively, by Gzip, bZIP, XZ, zip, compress command compression obtained by gunzip/gzip-d, bunzip/bzip-d, xzdec/xz-d, unzip, uncompress decompression. *. Z or *.GZ/*.BZ2/*.XZ

Linux Commands-umask: Display or set file mode mask values

The umask command controls the default permissions that are assigned to a file when it is created. It uses octal notation to remove a bitmask from the file-mode attribute.See the example below:0002 [[email protected] cmdline]$ Touch Foo.txt[[email

Make the program run in the background under Linux

First, why do you want to make the program in the background The procedures we calculate are very long, usually a few hours or even one weeks. The environment we use is to connect remotely to a Japanese Linux server using Putty. So the following

Linux: User and Group file interpretation (/etc/passwd,/etc/shadow,/etc/group,/etc/gshadow)

One, user files:/etc/passwd[[email protected] ~]# Cat/etc/passwdroot:x:0:0:root:/root:/bin/bash 1 2 3 4 5 6 7 |  | | |     |      |   | |  | | |     |      |   |--the default shell used by the user |  | | |     |   |--User Home Directory |  | | |   |

Linux Network programming: gethostbyname (), Getservbyname ()

ObjectiveRecently in the Learning Network programming, this article from my classmate Quake East, this article is also to record the studyGetHostByName ()This function can return the domain name information for a given domain name.Parameters: Domain

The principle and implementation of the Linux daemon

I. Overview of the daemon processMany services are turned on in Linux or UNIX operating systems when the system is booted, and these services are called daemons. For added flexibility, root selects the system-enabled mode, which is called the

Linux file Operation Cat, more, less, head, tail, WC commands

one, thecat command1, optional parameters-A,--show-all equivalent to -vet-B,--number-nonblank number of non-null output lines-e equivalent to -ve-E,--show-ends displays at the end of each line-N,--number all line numbers for the

Linux Punch 3

Review:Shell:type,which, environment variable path[Email protected] ~]# echo $PATH/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/binReference variable: ${variable name}Variable: A named memory space that can be found directly in

Linux Hosts.allow only allow ADSL dynamic IP login

"Scene" Companies using ADSL dial-up internet access, that is, the Internet access is dynamic IP.Server security Policy upgrade, only allow access to servers within the company.Implementation process:The server specifies a fixed IP can access the

Programming the memory usage for Linux CPU usage

Linux is available under the top, PS command to check the current CPU, mem usage. Here's a simple example:First, using PS to view the process of resource consumptionPs-auxWhen you view the process information, the third column is the CPU

How to install the OpenCV in Linux

Installation in LinuxThese steps has been tested for Ubuntu 10.04 and should work with other distros as well.Required Packages GCC 4.4.x or later CMake 2.6 or higher Git gtk+2.x or higher, including headers (Libgtk2.0-dev) Pkg-config

Hash table in the Linux kernel

Author:tiger-johnTime:2012-12-20Mail:[email protected]blog:http://blog.csdn.net/tigerjb/article/details/8450995Reprint please indicate the source.Preface: 1. Basic concepts:A hash table, also known as a hash table, is a data structure that is

Linux kernel hash lookup (1)

In the kernel, the lookup is essential, such as the kernel manages so many user processes, now to quickly locateA process, which needs to be looked up, and there are multiple virtual stores in the address space of a process, and the kernel is

The grep command in Linux-from cyber

1. RoleThe grep command in a Linux system is a powerful text search tool that uses regular expressions to search for text and print matching lines. grep full name is global Regular ExprEssion Print, which represents the global regular expression

Linux/dev Introduction and application of common special equipment [loop,null,zero,full,random]

Linux is a file-based system, and all hardware, such as software, will have a corresponding file representation under the directory. For Dev This directory, we know the file below it, which represents the Linux device. In Windows systems, devices

Network Configuration under Linux

First, modify the network parametersUnder Linux, modification parameters are divided into temporary modifications and permanent modifications . A parameter that is temporarily modified (modified by a command) restarts the service or system and

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