A concise tutorial of SQL statements for Linux---concatenate

Sometimes, we need to concatenate the data obtained from different fields. Each database provides a way to achieve this: Mysql:concat () Oracle:concat (), | | SQL Server: + The syntax for CONCAT ()

A concise tutorial of SQL statements for Linux---ALTER TABLE

Once the table is built into the database, we often find that the structure of the table needs to be changed. The common changes are as follows: Add a field Delete a field Change field name Change the data type of the field

Linux system Monitoring, diagnostic tool IO wait

1. Questions: recently in the real-time synchronization of the log, before the online is done a single part of the online log stress test, Message Queuing and client, the machine is no problem, but did not think of the second log, the problem came:

"Tuning of kernel parameters within Linux"

Tuning 1 Tuning 2 tuning 3vm.swappiness = Tennet.ipv4.tcp_syncookies = 1net.ipv4.tcp_tw_reuse = 1net.ipv4.tcp_tw_recycle = 1net.ipv4.tcp_fin_timeout =Net.ipv4.tcp_keepalive_time =Net.ipv4.ip_local_port_range = 1024x768

Settings for Linux environment variables

Environment variables in Linux are divided into system environment variables and user environment variables (as in window), System environment variables are valid for all system users, user environment variables are only valid for current users, we

Linux application Development-file programming-Library functions

---restore content starts---C library function file operation is independent of the specific system platform, the portability is good.Library functions-Create and openFile*fopen (const char*filename,const Char*mode)Mode: Open modesCommon open Mode:R,

The chmod of Linux

File/directory permission settings command: chmodThis is one of the most common commands used by Linux system administrators to change the access rights of a file or directory. There are two ways to use this command:Using text-setting methods that

Inputs from Linux are redirected from orientation and output

The standard inputs and outputs of Linux are as followsWhen we execute commands in Linux, the commands are output to the console by default, and many times we need to output the commands to other devices, such as the most common in the file, or in

Aeroo Reports Linux Server

This article covers installation process for Aeroo reporting engine on Linux servers. If you find the article useful or want to add some information related to this topic, please feel free to express your op Inion on Aeroo Reports & OpenOffice.org

Linux Special Symbols Encyclopedia

The special symbols commonly used in the shell are listed below:#   ;      ;;      .       ,/\ ' String ' |   !      $   ${}   $?   $$ $* "String" * * *?   : ^ $# [email protected] ' command ' {} [] [[]] () (()) | | && {Xx,yy,zz,...} ~ ~+ ~-& \ +-%=

Linux Compute program Run time

Turn from:Http://www.cnblogs.com/NeilHappy/archive/2012/12/08/2808417.html# include int gettimeofday (struct timeval *tv,struct timezone *tz);Strut Timeval {Long tv_sec; /* Number of seconds */Long tv_usec; /* microsecond number */};Gettimeofday

Linux Find command-atime,-ctime,-mtime the real meaning

The meaning of-atime,-ctime,-mtime under LinuxWe are often asked in forums or groups, how to view the creation date of a file under Linux or Unix?It's often said that with the Find command plus option-ctime, the-ctime here is not the create time,

Mawk of Linux commands

Pattern scanning and Text processing languageGrammar:Mawk [-F value] [-v var=value] [--] ' program text ' [File ...]Mawk [-F value] [-v var=value] [-F program-file] [--] [file ...]Describe:Awk is a text-processing language, and Mawk is an

Linux network-related configuration files

Linux systems generally fall into two main categories: 1, Redhat series: Redhat, Centos, fedora, etc. 2, Debian series: Debian, Ubuntu, etc.Linux system, TCP/IP network is configured through a number of text files, you need to configure these files

Introduction to the file structure of Linux

/ etc File SystemThe/etc directory contains a variety of system configuration files, some of which are described below. Other you should know which program they belong to and read the program's M a n page. Many network configuration files are also

Linux Learning (a): Linux change IP Address command _ Change dns_ change default gateway _ Change Subnet Mask _ host Name

How to use commands to change the IP, DNS, subnet mask of Linux, and add a Linux virtual machine on the virtual machine (Vitrualbox);Installation method: Http://pan.baidu.com/s/1sjJPhP7After installation, go to the Linux desktop, a desktop like this:

Linux judgment cacti version of template

There is often a "error:xml: Hash version does not exist" error that occurs when import download cacti template from the web. This is because the cacti of the export template and the cacti version of the import template are caused by different

Linux x64 under Compile Libjpeg

Libjpeg Compile: Download Libjpeg Source: http://www.ijg.org/, download jpegsrc.v9a.tar.gz Decompression source, command: TAR-ZXVF jpegsrc.v9a, source folder for jpeg-9a Run command:./configure--prefix=jpeg-9a/release

CPU, memory, IO, and network stress testing under Linux

First, a simple test of the CPU:1. Calculate special functions by BC commandExample: Calculating piecho "scale=5000; 4*a (1) "| Bc-l-Q MATH LIBRARYIf BC is invoked with THE-L option, a math library is preloaded and the default scale is set to 2

How to get the thread ID under Linux

Linux under the multi-threaded program occurs when Coredump, withGdb/path/to/program/file CoreYou can see all the threads[Email protected]:~/test/thread# gdb a.out CoreGNU gdb (GDB) 7.6.1Copyright (C) Free Software Foundation, Inc.License gplv3+:

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