How to run Linux commands in Java

Question

I want to create diff of two files  I tried searching for code in Java that does it  but didnt find any simple code  utility code for this  Hence  I thought if I can somehow run linux diff sdiff command from my java code and make it return a file that stores the diff then it would be great   Suppose there are two files fileA and fileB  I should be able to store their diff in a file called fileDiff through my java code  Then fetching data from fileDiff would be no big deal

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You can use java lang Runtime exec to run simple code  This gives you back a Process and you can read its standard output directly without having to temporarily store the output on disk  For example  here s a complete program that will showcase how to do it  import java io BufferedReader  import java io InputStreamReader   public class testprog       public static void main String args              String s          Process p          try               p   Runtime getRuntime   exec  quot ls -aF quot                BufferedReader br   new BufferedReader                  new InputStreamReader p getInputStream                  while   s   br readLine       null                  System out println  quot line   quot    s               p waitFor                System out println   quot exit   quot    p exitValue                 p destroy              catch  Exception e              When compiled and run  it outputs  line     line      line   classpath  line   project  line  bin  line  src  exit  0  as expected  You can also get the error stream for the process standard error  and output stream for the process standard input  confusingly enough  In this context  the input and output are reversed since it s input from the process to this one  i e   the standard output of the process   If you want to merge the process standard output and error from Java  as opposed to using 2 gt  amp 1 in the actual command   you should look into ProcessBuilder

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You can call run-time commands from java for both Windows and Linux   import java io     public class Test     public static void main String   args                    try                            Process process   Runtime getRuntime   exec  pwd       for Linux               Process process   Runtime getRuntime   exec  cmd  c dir      for Windows              process waitFor                BufferedReader reader   new BufferedReader new InputStreamReader process getInputStream                  String line                 while   line reader readLine     null                                   System out println line                                                              catch Exception e                                   System out println e                                finally                               process destroy                               Hope it Helps

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You need not store the diff in a 3rd file and then read from in  Instead you make use of the Runtime exec Process p   Runtime getRuntime   exec  quot diff fileA fileB quot    BufferedReader stdInput   new BufferedReader new InputStreamReader p getInputStream      while   s   stdInput readLine       null            System out println s

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Java Function to bring Linux Command Result   public String RunLinuxCommand String cmd  throws IOException        String linuxCommandResult           Process p   Runtime getRuntime   exec cmd        BufferedReader stdInput   new BufferedReader new InputStreamReader p getInputStream           BufferedReader stdError   new BufferedReader new InputStreamReader p getErrorStream           try           while   linuxCommandResult   stdInput readLine       null                 return linuxCommandResult                    while   linuxCommandResult   stdError readLine       null                return                     catch  Exception e            return                return linuxCommandResult

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if the opening in windows  try             chm file address         String chmFile   System getProperty  user dir       chm sample chm           Desktop getDesktop   open new File chmFile          catch  IOException ex            Logger getLogger Frame class getName    log Level SEVERE  null  ex                         JOptionPane showMessageDialog null   Terjadi Kesalahan    Error   JOptionPane WARNING MESSAGE

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try to use unix4j  it s about a library in java to run linux command  for instance if you got a command like  cat test txt   grep  Tuesday    sed  s kilogram kg g    sort  in this program will become  Unix4j cat  test txt   grep  Tuesday   sed  s kilogram kg g   sort

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Runtime run   Runtime getRuntime        The best possible I found is to construct a command which you want to execute     as a string and use that in exec  If the batch file takes command line arguments     the command can be constructed a array of strings and pass the array as input to     the exec method  The command can also be passed externally as input to the method     Process p   null    String cmd    ls     try         p   run exec cmd          p getErrorStream          p waitFor         catch  IOException e          e printStackTrace          System out println  ERROR RUNNING CMD        finally      p destroy

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You can also write a shell script file and invoke that file from the java code  as shown below       Process proc   Runtime getRuntime   exec    your script sh                               proc waitFor        Write the linux commands in the script file  once the execution is over you can read the diff file in Java   The advantage with this approach is you can change the commands with out changing java code

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The suggested solutions could be optimized using commons io  handling the error stream  and using Exceptions  I would suggest to wrap like this for use in Java 8 or later   public static List lt String gt  execute final String command  throws ExecutionFailedException  InterruptedException  IOException       try           return execute command  0  null  false         catch  ExecutionTimeoutException e    return null       Impossible case        public static List lt String gt  execute final String command  final long timeout  final TimeUnit timeUnit  throws ExecutionFailedException  ExecutionTimeoutException  InterruptedException  IOException       return execute command  0  null  true      public static List lt String gt  execute final String command  final long timeout  final TimeUnit timeUnit  boolean destroyOnTimeout  throws ExecutionFailedException  ExecutionTimeoutException  InterruptedException  IOException       Process process   new ProcessBuilder   command  bash    -c   command  start        if timeUnit    null            if process waitFor timeout  timeUnit                 if process exitValue      0                    return IOUtils readLines process getInputStream    StandardCharsets UTF 8                 else                   throw new ExecutionFailedException  Execution failed      command  process exitValue    IOUtils readLines process getInputStream    StandardCharsets UTF 8                            else               if destroyOnTimeout  process destroy                throw new ExecutionTimeoutException  Execution timed out      command                   else           if process waitFor      0                return IOUtils readLines process getInputStream    StandardCharsets UTF 8             else               throw new ExecutionFailedException  Execution failed      command  process exitValue    IOUtils readLines process getInputStream    StandardCharsets UTF 8                       public static class ExecutionFailedException extends Exception        private static final long serialVersionUID   1951044996696304510L       private final int exitCode      private final List lt String gt  errorOutput       public ExecutionFailedException final String message  final int exitCode  final List lt String gt  errorOutput            super message           this exitCode   exitCode          this errorOutput   errorOutput             public int getExitCode             return this exitCode             public List lt String gt  getErrorOutput             return this errorOutput            public static class ExecutionTimeoutException extends Exception        private static final long serialVersionUID   4428595769718054862L       public ExecutionTimeoutException final String message            super message

[java] How to run Linux commands in Java?

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