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Unix Linux vi Vim User manualAbout ViVi is the most popular full-screen document editor in the Unix world, and almost any UNIX machine can saywill provide this software. Linux Of course also has, its VI is actually Elvis (copyright question), but they allAlmost. Familiar with the DOS of the document processing, may feel that VI is not good, Unix has developedMany newer, better-used clerical editors, but not necessarily every Unix machine will install

Available memory: Available memory=free+buffers+cached, i.e. 2021=235+394+1392Memory used: Used memory=used-buffers-cached, 30217=32003-394-1392When using Zabbix's own template OS Linux template to monitor the server, used memory is found to be too high.This is because Zabbix uses the vm.memory.size[

Guide1. What is serialization?2. Why serialize? Where is the advantage?3. Four ways to serialize C + + objects4. The two most frequently used serialization scenarios use the experienceBody1. What is serialization?Program apes in writing applications often need to store some of the program's data in memory, and then write it to a file or transfer it to a network on a computer for communication. The process of converting program data into a format that

(P_partkey=L_partkey)WHEREP_brand='brand#35' andP_container= 'MED PKG') TouterJOIN (SELECTL_partkey asLp0.2 * avg(l_quantity) asLQ fromLineItemGROUP byl_partkey) Tinner on(Touter.l_partkey=TINNTER.LP)WHERETouter.l_quantityTinner.lqThis query has two occurrences of the LineItem table, group by and the two join IS L_partkey, so two subqueries and a join to use three jobs, now only need to use a job can be completed.However, rule-based optimization (RBO) does not solve all problems. There is

Tags: performance tuning database MySQL index database tuningThird, index 6. Several common possibilities for adding an index but not being used The previous talk about when not to use the index, but sometimes used is not necessarily used. Here are a few When an index was added but not used 1) Multi-column index que

Guide Vim is a text editor developed from VI. Code completion, compilation and error jumps and other convenient programming features are particularly rich, is widely used in programmers, and Emacs parallel to become UNIX-like system users favorite text editor. I. VI, VIM INTRODUCTION(1) Based on graphical interface, such as Gedit, geany, etc.;(2) based on the command line, such as Nano, VI, Joe, etc.;Each command line interface of the

transactions, but requires less overhead because fewer locks are needed to maintain. SQL Server can lock down the following resources (listed in order of increased granularity).Resource DescriptionThe RID line identifier. Used to lock a row in a table individually.The row lock in the KEY index. Used to protect the range of keys in a serializable transaction.PG 8,000-byte (KB) data page or index page.EXT a

Design patterns can help users abstract details at a higher level and better understand the architecture. If you are familiar with the GoF design pattern and the JavaServer Faces (JSF) framework, this article can help you gain insight into the design patterns used in the JSF framework and understand how they work. This article explores the design patterns used in the JSF framework. The design patterns dis

activity.startactivities () is often used to start other activity in the middle of an application. textutils.isempty () simple tool class for detecting whether null html.fromhtml () is used to generate an Html, and the argument can be a string. Personally, I don't think it's very fast, so I don't use it very often. (I say it is not often used to highlight this

js| Design Patterns can help users abstract details at a higher level and better understand the architecture. If you are familiar with the GoF design pattern and the JavaServer Faces (JSF) framework, this article can help you gain insight into the design patterns used in the JSF framework and understand how they work. This article explores the design patterns used in the JSF framework. The design patterns

The mutex embodies a kind of competition, I leave, inform you to come in. Cond embodies a kind of collaboration, I am ready to inform you to start. One obvious disadvantage of a mutex is that it has only two states: locked and unlocked. The condition variable, which compensates for the lack of a mutex by allowing the thread to block and wait for another thread to send the signal, is often used in conjunction with the mutex. When

Description1. Version used here: Springfox-swagger2 (2.4) Springfox-swagger-ui (2.4)2. Here is a description of the meaning and basic usage of common annotations (that is, the integration of swagger has been completed)Not integrated SeeSpringboot Integrated Springfox-swagger2 Build restful APISPRINGMVC Integrated Springfox-swagger2 Build restful APIWebsite WikiCommon notes:-@Api () for class;Represents a resource that identifies this class as a swagge

$ view become very large when there is a busy system activity, only a subset of the sessions are sampled and written to disk. By capturing only active sessions, Then only the associated set of data for the session being executed is generated, not the data for all sessions in the system. Using Ash allows you to v$active_session_history the current data and dba_hist_active_sess_ in the view Historical data in the history view for inspection and performance analysis, It is often possible to avoid t

,int *sign) Converts the floating-point value to a string and returns the stringChar *fcvt (double value,int ndigit,int *decpt,int *sign) Converts the floating-point value to a string and returns the stringChar *gcvt (double value,int Ndigit,char *buf) Converts the number of value to a string coexisting in BUF and returns a pointer to BUFChar *ultoa (unsigned long value,char *string,int radix) converts the unsigned integer value to a string and returns the string, radix is the base

Was asked in an interview the use of four kinds of smart pointers in STL Because of lack of experience, I only know auto_ptr and shared_ptr, and then said a weak ... Then the interviewer's cue was weak_ptr, and then he took the initiative to say Unique_ptr I only did a bit of use for auto_ptr and shared_ptr. Now in retrospect, the interview is still very dissatisfied with their own knowledge is also very dissatisfied, the recent work is not very busy, specifically to sum up the four kinds of sma

, characteristics and technical characteristics of history. ASCII Character Set 1. The origin of the name ASCII (American Standard Code for Information Interchange, American Information Interchange standard codes) is a computer coding system based on the Roman alphabet. 2. Features It is mainly used to display modern English and other Western European languages. It is the most common single byte coding system today and is equivalent to ISO 646.

Text Variable length, up to 65,535 characters Mediumtext Variable length, up to 2 of 24 square-1 characters Longtext Variable length, up to 2 of 32 square-1 characters The 1.char (n) and varchar (n) brackets mean the number of characters, not the number of bytes, so when Chinese is used (UTF8) means you can insert M Chinese, but it actually consumes m*3 bytes.2. At the same time c

99.999; Insert 123.456, the last query result is 99.999; Insert 12.34567, the last query result is 12.346; Therefore, in the use of floating-point type, but also to pay attention to the trap, to insert the actual results in the database will prevail.String data type MySQL data type Meaning CHAR (n) Fixed length, up to 255 characters VARCHAR (n) Variable length, up to 65,535 characters Tinytext Variabl