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Open files have a Fd:file descriptor (file descriptor)Standard input: Keyborad, 0Standard output: monitor, 1Standard error Output: monitor, 2I/O redirection: Changing the standard locationoutput Redirect: command > New_pos, command >>

1 View CPU 1.1 View the number of CPUs # Cat/proc/cpuinfo | grep "Physical ID" | Uniq | Wc-l 2 **uniq command: Delete duplicate rows; wc–l command: Count rows * * 1.2 View the number of CPU cores # Cat/proc/cpuinfo | grep "CPU Cores" | Uniq

sed (stream editor) Function Description: Use script to process text files.Syntax: sed [-hnv][-e][-f][text file]Additional Note: SED can process and edit text files according to script instructions.Parameters:-e or--expression= the input text file

1) PWD: Show working directory pathGrammar:PWD [Options]Options:The output link path when the-l directory is linked-P Output Physical pathExample:[Email protected] ~]# pwd/rootShow current Path2) CD: Change the working directory pathGrammar:CD

" What is Shell "Simple understanding, is the system with the computer hardware to use intermediate media, it is only a tool of the system. In fact, there is a layer of stuff between the shell and the computer hardware that is the system kernel. For

Because the front-end colleague needs to do a lot of special processing of Excel file, delete the specified line, so write this script, at the same time with Config.ini convenient for colleagues unfamiliar with PY use#!/usr/bin/env

Using cookies function _sethistory ($data){if (! $data | |!is_array ($DATA)){return false;}Determine if there is a browsing record in the cookie classif ($_cookie["_producthistory"]){$history = Unserialize (stripslashes ($_cookie[' _producthistory '

Introduction to MySQL MySQL is an open source relational database management system (RDBMS), the MySQL database system uses the most commonly used database management language-Structured Query Language (SQL) for database management. Stitching

Query optimization Technology of databaseQuery optimization Technology of databaseDatabase system is the core of MIS, and online transaction processing (OLTP) and online analytical Processing (OLAP) based on database is one of the most important

1. Basic jquery Object Set:$ (): JQuery object Collection Gets the elements in the jquery object set: Using the index to get JavaScript elements in the wrapper: var temp = $ (' img[alt] ') [0] Obtain JavaScript elements in the jquery object set

Some of the orders to be used in 2016/7/3 are recorded here, to be continued ... 2016/7/4 More ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ View IP Address: windows:ipconfig/allLinux:ifconfig Ifdown disable the

Three information on MySQL: Information about the results of the query: This includes the number of records produced by any select,update or DELETE statement. Table and Database information: This includes information about the structure of

English title: Useful one-line SCRIPTS for SED (Unix stream editor)Original title: HANDY one-liners for SED (Unix stream editor) Finishing: Eric pement-e-mail: pemente[at]northpark[dot]edu version 5.5Translator: Joe-e-mail: hq00e[at]126[dot]com The

1 View CPU 1.1 View the number of CPUs # Cat/proc/cpuinfo | grep "Physical ID" | Uniq | Wc-l 2 **uniq command: delete duplicate rows; wc–l command: Count rows * * 1.2 View the number of CPU cores # Cat/proc/cpuinfo | grep "CPU Cores" | UniqCPU

Search based on keyword Command grep is used to search for text based on keywords $ grep ' Shuangde '/etc/passwd $ find/-user Shuangde | grep video -I ignores case when searching -N Displays the number of rows in which the result -V output lines

SQLite is lightweight, after compilation is very small, one of the reasons is that in the query optimization is relatively simple, it is only using the index mechanism to optimize, after the analysis of the query optimization of SQLite and the study

Aggregate is the more important of the many tools that MongoDB provides, similar to the one in SQL statements GROUP BY . The aggregation tool allows developers to manipulate data in the database directly using MongoDB native commands, and aggregates

Table record Add and delete change---Insert table record inserts--Inserting a piece of dataINSERT [INTO] table_name (field name,...) Values (value,...);---inserting multiple dataINSERT [INTO] table_name (field name,...) Values (value,...),(Value,...)

Iv. conclusion of the experiment1. Practice command history, aliases, and special character usages in the shell (4th. 4.2, Section ~4.5)2. Shell Command Application Exercise(1) The use of the following documents is briefly reviewed through the Help

1. View Ipifconfig or IP A2. Restart the reboot3. Shutdown shutdown-h now4. Stop CTRL+C5. Restart the network or one of the Services service network restart II. directories and Operations commands 6. View the working directory