Weekly note 20141101

1. Check the current Linux System Version: lsb_release-. You can also view the version information in/etc/RedHat-realse. LSB is short for Linux Standard base.

2. The MV command can be used to move or rename directories or files, as follows:
MV/home/ABC/home/ABCD

3. Replace the string content in the file:
Find-name 'file name to be searched' | xargs Perl-pi-E's | replaced string | G'
Replace the strings in Multiple folders:
Sed-I "s/original string/New String/g" 'grep original string-rl directory'

4. decompress the ZIP file: unzip **. Zip

5. DF to view the capacity of each main directory. DF-H is displayed in MB and G.

6. Unsupported Major. Minor version 51.0 (unable to load class app. Common. listener. menulistener) exception Java compilation version is incorrect.
The error of Java. Lang. unsupportedclassversionerror occurs because we use the Java class file compiled by JDK of a higher version to try to run on the JVM of a lower version,
The error message. Because the format of the class file generated by JDK of a higher version may be different from that of JDK of a lower version. Class. In this way, the JVM of earlier versions cannot be interpreted and executed.
This. Class file will throw a class version error not supported by Java. Lang. unsupportedclassversionerror.
You need to modify the Java compilation version of the current project.
Modification method:
Choose project> right-click --> Properties> JAVA compile. Select the corresponding version. Note that if there is no corresponding version of JRE in eclipse, You need to manually add it.

7. Copy (CP) to the current directory in Linux. The current directory is represented. For example, CP/APP/test.txt.

8. Different DB2 database versions may cause many problems due to different jar packages.

9. When Tomcat is started, check the log Catalina. Out to check whether the project is started normally. You can also check the localhost log for errors.

11. java. Lang. illegalargumentexception: Can't convert argument: NULL cause:
Myeclipse automatically updates and deploys the Web. xml file and re-generates the header Declaration of the XML file when modifying the project name. The Java name is added:
<Javaee: param-Name> encoding </javaee: param-Name>. You can remove this javaee. Generally, it will modify the servlet configuration.

12. jar-cvfm0 game. War./0. This is an Arabic number. It only means packaging without compression.
Jar-xvf game. War to the current directory

13. Update table name set column name = new value where column name = A Value
Delete from table name where column name = Value

14. The netstat-TLN command is used to view Linux port usage.

15. l exception: can bind a long value only for insert into a long column:
The reasons are as follows:
1). The length of the inserted string is greater than 4000 bytes.
2 ). the actual length of a field data inserted into the record in the table is greater than 2000 bytes (if it is a UTF-8, It is 1333 bytes ); or the inserted record contains two or more strings with a length greater than 2000 bytes.
3). The JDBC driver of the database and the client does not match.

Weekly note 20141101