count rows

1, vi Command (editor)Enter VI commandVI filename: opens or creates a new file and places the cursor at the beginning of the firstVI +n filename : Opens the file and places the cursor at the beginning of nthVI + filename : Opens the file and places

Experience:What is the difference between 1,where and having?where is the filter used for the original field,Having is primarily used for aggregate filtering of aggregation functions, although this primitive field is also useful, but not recommended,

#include "lrd.h"Action () {double trans_time; Defines a double type variable to hold the transaction execution timestatic Lrd_init_info Initinfo = {Lrd_init_info_eyecat};static lrd_default_db_version dbtypeversion[] = {{lrd_dbtype_odbc,

1.1 Viewing the number of CPUs# Cat/proc/cpuinfo | grep "Physical ID" | Uniq | Wc-l2 **uniq command: delete duplicate rows; wc–l command: Count rows * *1.2 Viewing CPU Cores# Cat/proc/cpuinfo | grep "CPU Cores" | UniqCPU Cores:41.3 View CPU Models#

Recently learning Linux, the teacher class said the estimated class is forgotten, is now ready to prepare for a rainy days.Ps1=x//Modify the terminal promptsu root//switch user ssh [email protected]192.168.116.129//Encrypt remote connectionYum-y

Shell special Characters * Any of the characters ? Any one character #注释字符 \ de-Semantic characters | pipe character $ variable prefix,!$ combination, regular inside means end of line Multiple commands are written to

YII2, by default, generates a model that directly operates on a single table and has search and paging and sorting capabilities, and in many complex business logic requirements, a single table operation is difficult to achieve the effect we want,

Shell Special Symbol _cut command概念：cut命令用来截取某一个字段格式：cut -d ‘分割字符‘ [-cf] n,这里的n是数字，该命令选项有如下几个：- d 后面跟分割字符，分割字符要用单引号括起来- c 后面接的是第几个字符- f 后面接的是第几个区块The Cut command uses the following [Email protected] do]# cat/etc/passwd

8.10 Shell Special Symbol Cut commandCommand: CutUsed to intercept a fieldSyntax: cut-d ' delimited character ' [-CF] n Here's n is the number-D: followed by delimited characters, separated by single quotation marks-C: followed by the first few

8.10 Shell Special symbol Cut commandSpecial symbols (top):A 1.* represents 0 or more arbitrary characters.2. Represents only one arbitrary character ( whether it is a number or a letter, as long as it can be matched. )3.# This symbol in Linux

MySQL Meta DataYou may want to know the following three kinds of information about MySQL: Query Result information: The number of records affected by the SELECT, UPDATE, or DELETE statement. Database and data table information: contains

Special symbols for Liunx Represents a number of letters or numbers？ Any one character"#" Comment\ de-Semantic characters| Pipe character 1.* represents any arbitrary character or number[[email protected]/]# ls *.txt1.txt[Email

cut : Intercepts a fieldSyntax: cut-d "separator character" [-CF] n here n is the number-D: followed by delimited characters, delimited by double quotation marks-C: followed by the first few characters-F: The next section is followed by the number

First, shell special symbol Cut commandA command that intercepts a field: cut-D: followed by delimited characters, separated by single quotation marks-C: followed by the first few characters-F: The next section is followed by the number of blocks-D

I. Text editing commandsVI may be used in Linux more frequent text editor, if not proficient in the use of VI, to a certain extent, will affect the efficiency, so here to record the VI's common commands and operating methodsin [[email protected] ~]#

Shell Variables1. Order env to list all system variables (all uppercase letters) of system presets2. The command set can see the variables that are preset by the system, or you can see the user-defined variables.3. Custom variables:Rules for

Shell Features--Linux has a variety of shells to use, the default for Bash,bash has the following key features.1. Command Memory AbilityPress the up and down keys on the command line to find a pre/Post input command. These commands are recorded in ～/

1. Network Environment View command:1.1 ifconfig command: View and configure network commands1.2 Turn off and start the NIC: Ifdown/ifup NIC device name-disables and enables the NIC device1.3 Querying network Status:Netstat option (-TULN: The

User ManagementID: You can view the current userWHOAMI: Viewing the current userWho: See who is currently logged inW: can also seeAdd userUseradd Zhaoyuanyuan Adding usersUseradd-g GroupName Uernamepasswd ZhaoyuanyuanThe user's default home

1.url does not write the port number, the default is 80 port; This machine is 127.0.0.1 or localhost2. User ManagementView Current User:ID: can view the current user; WhoAmI: view the current user; Who: can view the currently logged in user; W: can