• Basic syntax and variables of shell programming


    I. basic format of shell script writing Take the simplesthello wordGive an example .#!/bin/bash echo ‘hello world’ . / bin / bash: tell the computer to use the bash interpreter to execute the code Echo: printing II. Running shell script Method 1(recommended) chmod 777 myshell.sh #Give file permission ./myshell.sh #Running files Method 2 sh myshell.sh […]

  • 15 advanced interview questions of vue.js


    Crazy technology house https://www.zeolearn.com/inte… No reprint without permission 1. When rendering the item list, what is the function and importance of the key attribute? When you render a list of projects,keyProperty allows Vue to track each vnode. The key value must be unique. If the key attribute is not used, and the contents of the […]

  • New features of ES6


    ECMAScript 6 is the version released by ECMA on June 2015. As a demarcation point, now we usually call these later versions ES6. ES6 has brought a lot of new syntax and added the concept of class. It can be predicted that JavaScript is moving towards an engineering language. We don’t know whether this is […]

  • Go development guide for novices


    It has been more than three months since I joined the ant. During this period, I mainly maintain a server written by go. Although it didn’t take long, I still accumulated some experience. Here is a summary for the students who want to try go.This article will introduce the design concept, development environment and language […]

  • Oracle practice (1)


    I. creation and deletion of tablespaces Declaration: this operating environment is windows, Oracle10g Tablespace? Logical unit of the Oracle database. data base 一个data base下可以建立多个表空间,一个表空间可以建立多个用户、一个用户下可以建立多个表。 create tablespace test datafile ‘c:\test.dbf’ size 100m autoextend on next 100m; Test is the tablespace name Datafile specifies the data file corresponding to the tablespace The initial size of the tablespace […]

  • IOS – about some rounding methods


    1. Direct conversion float k = 1.6; int a = (int)k; NSLog(@”a = %d”,a); The output is 1, (int) is a forced type conversion, which directly discards the decimal part of the floating-point number. 2. Rounding of floor function (rounding down) float k = 1.6; int a = floor(k); NSLog(@”a = %d”,a); The output result […]

  • How should we rank requirements?


    Abstract:Demand management is an art. When developing products, we will face various and endless demands every day, some from external users’ feedback, some from internal team’s idea, some from product’s bug, some new functions It seems that as long as all the demands are realized, the product can become better, then attract more users, then […]

  • Nodejs from introduction to advanced one (basic part)


    I. Basic knowledge of node.js 1, concept Simply put, node.js is the JavaScript running on the server side. Node.js is the running environment of JavaScript Node.js uses an event driven, non blocking I / O model to make it lightweight and efficient. 2. Installation and use Download address: http://nodejs.cn/ Nodejs5 basic objects: 1. Require import […]

  • Fine derivation machine learning: the principle of logistic regression model


    Logistic regression (classification) Sigmoid function and binomial logistic regression model \(sigmoid\)The function is: \[ sigmoid(x)=\pi(x)=\frac{1}{1+e^{-x}}\\ \]among\(x \in \mathbb{R}\),\(sigmoid(x)\in (0,1)\). And its derivative \[ \pi'(x)=\pi(x)(1-\pi(x))\\ \] Binomial logistic regression model is the conditional probability distribution as follows: \[ P(Y=1|x)=\frac{exp(w \cdot x+b)}{1+exp(w \cdot x+b)}\\ P(Y=0|x)=\frac{1}{1+exp(w \cdot x+b)}\\ \]among\(x \in \mathbf{R}^{n}\),\(Y \in\{0,1\}\)For output,\(w \in \mathbf{R}^{n}\)and\(b \in \mathbf{R}\)As parameters\(w\)Is […]

  • MySQL data section (5) – SQL performs monthly statistics on data or weekly statistics on data


    For all requirements, when you don’t know how to deal with them, you should first use the simplest method, or to be clear, use the most original method, and implement the business requirements first. I. summarize and count the withdrawal queue data table “IMS” checkout “task, and summarize and count the total amount and times […]

  • C language writes the current system time (log) to the txt file


      The program implementation is very simple, involving only two knowledge points. 1. The most basic opening and closing of files;2. Acquisition of system time. The code is written in the vs2019 environment,Some functions are not recognized in other compilers。 You can only find the corresponding function by yourself and simply modify it. If you […]

  • Oracle columns are merged and spliced with splices — Usage of listag function


    ==Note: it is not supported after wm_concat (STR1) 11g== Listag function usage select LISTAGG(name, ‘,’) WITHIN GROUP (ORDER BY id) from tableName