How to work with rpm packages installation, upgrade and roll-back, delete?

• The following rpm command installs Mysql client package.

             # rpm -ivh  MySQL-client-3.23.57-1.i386.rpm

• You can use rpm command to query all the packages installed in your system.

             # rpm -qa
             # rpm -qa | grep MySQL-client

• Query a Particular RPM Package using rpm -q

              # rpm -q MySQL-client

• Information about Installed RPM Package using rpm -qi

             # rpm -qi MySQL-client

• If you have an RPM file that you would like to install, but want to know more information about it before installing, you can do the following:

                # rpm -qip MySQL-client-3.23.57-1.i386.rpm

• List all the Files in a Package using rpm -qlp

               $ rpm -qlp MySQL-client-3.23.57-1.i386.rpm

• Uninstalling a RPM Package using rpm -e

                 # rpm -ev MySQL-client

• Upgrading a RPM Package using rpm -Uvh

                  # rpm -Uvh MySQL-client-3.23.57-1.i386.rpm

• Downgrade or rollback rpm to old version

                # rpm -Uvh --oldpackage "~/MySQL-client-3.23.57-1.i386.rpm"

How to know TCP/IP port listening or free in UNIX / Linux?

Use netstat command in linux / unix and grep for a port number

>netstat -anp | grep <port_number>

How to export and import mysql dump ?

To take export / backup of mysql DB, use following command

>mysqldump -u <db_username> -p<db_password> -h<db_host> db_name  > db_name_backup.sql

To take export / backup of table in mysql DB, use following command
 
>mysqldump -u <db_username> -p<db_password> -h<db_host> table_name > table_name_backup.sql

Similarly To import or dump the data into mysql database use following command
 
>mysql -u <db_username> -p<db_password> -h<db_host> db_name < ~/db_name_backup.sql (ensure db_name_backup.sql present in home directory)

How to kill Some Java Process without Input PID?

To extract the PID use awk command and send the argument to xargs command.

ex: To kill activemq process use the below command

ps -ef | grep $USER | grep java | grep activemq | awk '{print $2}' | xargs kill -9

How to analyze how much time a program spends in each part of the code?

    To do this analysis use -prof option, like below.

F:\JavaSamples>java -prof Test
Hello World!
Dumping CPU usage in old prof format ... done.

F:\JavaSamples>dir

After running java application, The JVM dumps the each part of code / api calls into a seperate file named  java.prof

java.prof:
count callee caller time
1375 java.lang.AbstractStringBuilder.ensureCapacityInternal(I)V java.lang.AbstractStringBuilder.append(C)Ljava/lang/AbstractStringBuilder; 0
1306 java.lang.String.charAt(I)C java.lang.String$CaseInsensitiveComparator.compare(Ljava/lang/String;Ljava/lang/String;)I 15
759 java.io.WinNTFileSystem.isSlash(C)Z java.io.WinNTFileSystem.normalize(Ljava/lang/String;II)Ljava/lang/String; 0
759 java.lang.String.charAt(I)C java.io.WinNTFileSystem.normalize(Ljava/lang/String;II)Ljava/lang/String; 0
755 java.lang.CharacterDataLatin1.getProperties(I)I java.lang.CharacterDataLatin1.toLowerCase(I)I 0
755 java.lang.CharacterDataLatin1.toLowerCase(I)I java.lang.Character.toLowerCase(I)I 0
..

How to compile and run java code in EditPlus?

Run EditPlus,

Navigate to Tools --> Configure User Tools -->

1. Change GroupName to javac
2. Add Tool like below

and also for java

finally use the user tools from tool bar
That all..

How to start learning java?

   To start learning java, you need JDK (Java Development Kit) and some text editor like EditPlus or power full IDE like Eclipse

Download the JDK from Oracle site and install it.

Set Environment variable PATH and CLASSPATH

Write a sample java program with the text editor and compile with javac compiler

and run the class with java tool / JVM

MainClass.java :

public class MainClass {

    public static void main(String[] args) {

        System.out.println("Java");

    }

}

>javac MainClass.java

>java MainClass

You may get compile time or runtime error if you not properly set Environment variables

PATH must point to bin directory of JDK like C:\Program Files\Java\jdk1.8.0_45\bin

CLASSPATH must point to lib directory of JDK / JRE like C:\Program Files\Java\jdk1.8.0_45\jre\lib or C:\Program Files\Java\jre1.8.0_51\lib

choose JDK's JRE for better compatibility