adding classpath in linux

Question

export CLASSPATH      somejar jar    mysql-connector-java-5 1 6-bin jar java -Xmx500m folder subfolder   dit1 some xml cd      is the above statement for setting the classpath to already existing classpath in linux is correct or not

User · Answer

It s always advised to never destructively destroy an existing classpath unless you have a good reason   The following line preserves the existing classpath and adds onto it   export CLASSPATH   CLASSPATH foo jar    bar jar

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I don t like setting CLASSPATH  CLASSPATH is a global variable and as such it is evil     If you modify it in one script  suddenly some java programs will stop working   If you put there the libraries for all the things which you run  and it gets cluttered  You get conflicts if two different applications use different versions of the same library  There is no performance gain as libraries in the CLASSPATH are not shared - just their name is shared  If you put the dot     or any other relative path in the CLASSPATH that means a different thing in each place - that will cause confusion  for sure    Therefore the preferred way is to set the classpath per each run of the jvm  for example   java -Xmx500m -cp       somejar jar    mysql-connector-java-5 1 6-bin jar      folder subfolder   dit1 some xml   If it gets long the standard procedure is to wrap it in a bash or batch script to save typing

User · Answer

For linux users  and to sum up and add to what others have said here  you should know the following    Global variables are not evil    CLASSPATH is specifically what Java uses to look through multiple directories to find all the different classes it needs for your script  unless you explicitly tell it otherwise with the -cp override   The colon       character separates the different directories   There is only one  CLASSPATH and it has all the directories in it   So  when you run  export CLASSPATH       you want to include the current value   CLASSPATH  in order to append to it   For example   export CLASSPATH   export CLASSPATH  CLASSPATH  usr share java mysql-connector-java-5 1 12 jar   In the first line above  you start CLASSPATH out with just a simple  dot  which is the path to your current working directory  With that  whenever you run java it will look in the current working directory  the one you re in  for classes   In the second line above   CLASSPATH grabs the value that you previously entered     and appends the path to a mysql dirver   Now  java will look for the driver AND for your classes  echo  CLASSPATH   is super handy  and what it returns should read like a colon-separated list of all the directories you want java looking in for what it needs to run your script  Tomcat does not use CLASSPATH  Read what to do about that here  https   tomcat apache org tomcat-8 0-doc class-loader-howto html

User · Answer

Important difference between setting Classpath in Windows and Linux is path separator which is      semi-colon  in Windows and      colon  in Linux  Also  PATH  is used to represent value of existing path variable in Windows while   PATH  is used for same purpose in Linux  in the bash shell   Here is the way to setup classpath in Linux   export CLASSPATH   CLASSPATH   new path   but as such Classpath is very tricky and you may wonder why your program is not working even after setting correct Classpath  Things to note    -cp options overrides CLASSPATH environment variable  Classpath defined in Manifest file overrides both -cp and CLASSPATH envorinment variable    Reference  How Classpath works in Java

User · Answer

Paths under linux are separated by colons      not semi-colons      as theatrus correctly used it in his example   I believe Java respects this convention  Edit Alternatively to what andy suggested  you may use the following form  which sets CLASSPATH for the duration of the command   CLASSPATH  quot      somejar jar    mysql-connector-java-5 1 6-bin jar quot  java -Xmx500m      whichever is more convenient to you

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