I'm currently working on a web application that involves mounting a drive and extracting a tar.gz file, all in Java. Since the application runs in a linux environment, I figured I'd try using unix commands like "mount" and "tar".
Runtime runtime = Runtime.getRuntime();
Process proc;
String mountCommand = "mount -t cifs -o username=...";
String extractCommand = "tar xzf ..."
proc = runtime.exec(mountCommand);
proc.waitFor();
proc = runtime.exec(extractCommand);
proc.waitFor();
Running the mount command and extract command in the terminal works fine, but fails when FIRST run in java. The second proc.waitFor() returns exit code 2. However, running this code after the first failed attempt works fine. I have a feeling that the problem is that waitFor() isn't waiting until the mount command is fully completed. Am I missing anything important in my code?
Also, I'd rather do this all in Java, but I had a really hard time figuring out how to untar a file, so I'm taking this approach. (oh if anyone can tell me how to do this i would be very happy). Any suggestions would be muuuuuuuuuuch appreciated!
Making progress. In case anyone was wondering, here is how I am extracting a tar.gz file in Java. Put together from a few online tutorials.
public static void extract(String tgzFile, String outputDirectory)
throws Exception {
// Create the Tar input stream.
FileInputStream fin = new FileInputStream(tgzFile);
GZIPInputStream gin = new GZIPInputStream(fin);
TarInputStream tin = new TarInputStream(gin);
// Create the destination directory.
File outputDir = new File(outputDirectory);
outputDir.mkdir();
// Extract files.
TarEntry tarEntry = tin.getNextEntry();
while (tarEntry != null) {
File destPath = new File(outputDirectory + File.separator + tarEntry.getName());
if (tarEntry.isDirectory()) {
destPath.mkdirs();
} else {
// If the parent directory of a file doesn't exist, create it.
if (!destPath.getParentFile().exists())
destPath.getParentFile().mkdirs();
FileOutputStream fout = new FileOutputStream(destPath);
tin.copyEntryContents(fout);
fout.close();
// Presserve the last modified date of the tar'd files.
destPath.setLastModified(tarEntry.getModTime().getTime());
}
tarEntry = tin.getNextEntry();
}
tin.close();
}
Quick Answer
Since a dependency on external commands exists, simplify it like this:
#!/bin/bash
mount -t cifs -o username=...
tar xzf ...
Name it mount-extract.sh then call it using a single Runtime.exec() call.
Semi-integrated Answer
Use Java APIs.
http://java.sun.com/j2se/1.4.2/docs/api/java/util/zip/GZIPInputStream.html
http://www.jajakarta.org/ant/ant-1.6.1/docs/ja/manual/api/org/apache/tools/tar/TarInputStream.html
You will need Runtime.exec to execute the mount command.
Forward Looking
Since Java is a cross-platform software development tool, consider abstracting the mount command in your application to be derived dynamically based on the underlying operating system.
See: How can I mount a windows drive in Java?
See: http://java.sun.com/j2se/1.4.2/docs/api/java/lang/System.html#getProperties()
Of course, Agile development would insist that this not be done until it is needed. So keep it in the back of your mind until then (as you might never run the application on anything but Unix-based systems).
Take a look at the org.apache.tools.tar package in the Ant codebase. There is a class in that package, TarInputStream, that can be used to read tar archives.
It may be related to the way you call the method.
See this answer
Basically try using
.exec( String [] command );
instead of
.exec( String command );
I'm not sure if it is even related, because you mention it runs the second time. Give it a try and let us know.
This can all be done in Java, but you have to be aware of caveats when dealing with native processes.
The waitFor() command may not be doing what you hope: if the process you started has a child process that does the actual work you need then the waitFor(), which returns when the parent process has finished, has not allowed enough time for the child process to finish.
One way to get around this is to loop over some test to see that the native processes you started have finished to your satisfaction---in this case perhaps checking if some java.io.File exists.
Related
I'm trying to use the Java function Runetime.exec(String) to run a program in the startup folder of a windows 7 computer like so:
Runtime.getRuntime().exec(runner.getPath() + "\\run.bat");
And when I run this I get an error saying the command cannot be run:
Exception in thread "main" java.io.IOException: Cannot run program ""C:\Users\ly
ndsey\AppData\Roaming\Microsoft\Windows\Start": CreateProcess error=2, The syste
m cannot find the file specified
As you can see, the file name is cut off at the "\Windows\Start" when it should continue to "\Windows\Startup\run.bat".. Is there an alternative I can use?
Considering runner as a File instance, this should work.
Desktop.getDesktop().open(new File(runner, "run.bat"));
It uses Desktop class instead of Runtime, so you don't have to convert your File (runner) to its String representation (which is error prone). Runner is now used 'as is' as the parent directory of the "run.bat" you want to execute.
Other advantage of Desktop class : you can now open any file you want.
As an alternative you can use ProcessBuilder. I feel ProcessBuilder is more safe than Runtime.getRuntime().exec http://docs.oracle.com/javase/7/docs/api/java/lang/ProcessBuilder.html
String[] command = {"CMD", "/C", "dir"};
ProcessBuilder pb = new ProcessBuilder( command );
//set up your work directory if needed
pb.directory(new File("c:\\path"));
Process process = pb.start();
as i can see from the error you give, and i hope it's a copy past, you string runner.getPath() for some reason start and end with "\"" which make the whole path invalid. check that and remove it if needed
if you have the file already and you just need it's path you can use
runner.getAbsolutePath()
also, if runner is a file, getPath will give you the file path including the path, so your code will surely won't work. instead use:
String path = runner.getPath();
path = path.substring(0, path.lastIndexOf("\\")) + "\\run.bat";
Runtime.getRuntime().exec(path);
You should avoid the exec(String) method, which attempts to parse the entire string into command + arguments. The safe option is exec(String[]), which presupposes the first array element is the command and the rest are arguments.
So, writing
Runtime.getRuntime.exec(new String[] { yourCommandString })
is a surefire way of getting the right message across.
I'm trying to convert files from png's to pdf using imagemagick and Java. I've got everything working to a place when I'm executing imagemagick command to actually merge multiple png's into one pdf. The command itself looks properly, and it works fine when executed in the terminal but my application gives me error showing that imgck can't open the file (even though it exists and I've set permissions to the folder to 777 :
line: convert: unable to open image `"/Users/mk/Documents/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/sch-java/print-1357784001005.png"': No such file or directory # error/blob.c/OpenBlob/2642.
This is my command :
/opt/local/bin/convert "/Users/mk/Documents/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/sch-java/print-1357784001005.png" "/Users/mk/Documents/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/sch-java/print-1357784001219.png" "/Users/mk/Documents/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/sch-java/complete-exportedPanel2013-01-1003:13:17.212.pdf"
And my Java code :
String filesString = "";
for (String s : pdfs){
filesString += "\""+ s + "\" ";
}
Process imgkProcess = null;
BufferedReader br = null;
File f1 = new File(pdfs[0]);
//returns true
System.out.println("OE: "+f1.exists());
String cmd = imgkPath+"convert "+ filesString+ " \""+outputPath+outName+"\"";
try {
imgkProcess = Runtime.getRuntime().exec(cmd);
InputStream stderr = imgkProcess.getErrorStream();
InputStreamReader isr = new InputStreamReader(stderr);
br = new BufferedReader(isr);
} catch (IOException e1) {
msg = e1.getMessage();
}
imgkProcess.waitFor();
while( (line=br.readLine() ) != null){
System.out.println("line: "+line);
}
The whole code is executed from a java servlet controller after getting request from a form. Any ideas what can cause this ? I'm using latest imgck, jdk, and osx 10.7 .
A few things:
When spawning anything but really trivial processes, it's usually better to use ProcessBuilder than Runtime.exec() - it gives you much better control
Even with ProcessBuilder, it often works better to write a shell script that does what you need. Then spawn a process to run the script. You get a lot more control in shell script than you do in ProcessBuilder
Remember that a spawned process is not a shell. It can't, for instance, evaluate expressions, or expand shell variables. If you need that, then you must execute a shell (like sh or bash). Better yet, write a shell script as described above
If all you need to do is to execute some ImageMagick commands, it would probably be easier to jmagick, a Java interface to ImageMagick - see http://www.jmagick.org/
Actually, since the you're assembling images into a PDF, the iText library - http://itextpdf.com is probably the best tool for the job, as it is native Java code, does not require spawning a native process, and will therefore be much more portable.
Solved it by adding all arguments to an arrayList and then casting it to String array.
ArrayList<String> cmd = new ArrayList<String>();
cmd.add(imgkPath+"convert");
for (int i=0, l=pdfs.length; i<l; i++){
cmd.add(pdfs[i]);
}
cmd.add(outputPath+outName);
imgkProcess = Runtime.getRuntime().exec(cmd.toArray(new String[cmd.size()]));
I try to delete a file on OSX via Java and it doesn't work.
Runtime runtime = Runtime.getRuntime();
Process process = runtime.exec(new String[] { "/bin/bash", "-c", "rm file.pdf" });
Any idea?
You don't need to execute a shell command to do this. In fact, using a shell command to do this will make your app platform-specific, rather than platform-independent.
Simply create a reference to the file, and call the delete() method:
File fileToDelete = new File("/path/to/file").delete();
There are also methods on the File class that allow you to create temporary files.
The delete on exit functions should be avoided, as noted by Alexander's comment, and this bug/proposed fix on the Oracle support pages.
NOTE: All file access (reading, writing, deleting) is run through a SecurityManager, so if the user under which your application is running doesn't have the necessary security rights to the file in question, these operations may fail. If you simply keep your app running in user space, are only accessing files that the user has access to, or are only dealing with temporary files, you should be fine.
You can do this to delete your file.
try{
File f1 = new File("path to file");
boolean success=f1.delete();
if(!success){
// Notify user that the file
}
}catch(SecurityException ex){
// No sufficient rights to do this operation
}
As normalocity had mentioned java.io.File class has a method to delete a file
For fancier file/directory operations you may want to check out FileUtils from apache.
I am trying to write a unix terminal emulator in java. I am having a lot of trouble. It doesn't seem like I can change the working directory of the program, so commands like "cd" aren't working properly. My question is this, If I run a command that requires input from the user, is there any way to send that input to the running process?
Thanks so much, that was a lot of help. Here's an example:
InputStream in = null;
OutputStream outS = null;
StringBuffer commandResult = new StringBuffer();
String line = null;
int readInt;
p = Runtime.getRuntime().exec("gksudo apt-get install firefox");
int returnVal = p.waitFor();
in = p.getInputStream();
while ((readInt = in.read()) != -1)
commandResult.append((char)readInt);
outS = (BufferedOutputStream) p.getOutputStream();
outS.write("Y".getBytes());
outS.close();
System.out.println(commandResult.toString());
in.close();
This is the output:
Reading package lists...
Building dependency tree...
Reading state information...
The following packages were automatically installed and are no longer required:
libmono2.0-cil libmono-data-tds2.0-cil libmono-system-data2.0-cil
libdbus-glib1.0-cil librsvg2-2.18-cil libvncserver0 libsqlite0
libmono-messaging2.0-cil libmono-system-messaging2.0-cil
libmono-system-data-linq2.0-cil libmono-sqlite2.0-cil
libmono-system-web2.0-cil libwnck2.20-cil libgnome-keyring1.0-cil
libdbus1.0-cil libmono-wcf3.0-cil libgdiplus libgnomedesktop2.20-cil
Use 'apt-get autoremove' to remove them.
The following extra packages will be installed:
firefox-globalmenu
Suggested packages:
firefox-gnome-support firefox-kde-support latex-xft-fonts
The following NEW packages will be installed:
firefox firefox-globalmenu
0 upgraded, 2 newly installed, 0 to remove and 5 not upgraded.
Need to get 15.2 MB of archives.
After this operation, 30.6 MB of additional disk space will be used.
Do you want to continue [Y/n]? Abort.
Why is it aborting before I can pipe in the "Y"?
Yes; see Process#getOutputStream() to get the "standard input" (stdin) stream for a Process object.
As for the issue of changing directory, I don't believe the JVM can change its working directory once it has launched. However, your program could model the idea of the "current working directory" as a variable which it uses when it does things which are relative to that location (e.g. launching processes, listing directory contents, etc). The ProcessBuilder class even has a way to set the working directory for Processes it produces.
I'm running a windows program from within java:
String command = "cmd /C start "+fileName+".bat";
Runtime rt = Runtime.getRuntime();
Process pr = rt.exec(command, null, new File(currWD));
int exitValue = pr.waitFor();
The program completes successfully (exitValue == 0) and creates a file "fileName" in the working directory. I am trying in the same routine to find the size of this file:
xmlFileSize = (new File(fileName)).length();
Java finds the file yet it appear to be empty (xmlFileSize == 0). Once Java finishes I can see, however, that the file is non-empty.
How can I resolve this? All I want is that Java can correctly assesses the size of the file created by the windows program that Java has executed.
A zero-length file indicates that the file may not exist. From the docs:
The length, in bytes, of the file denoted by this abstract pathname, or 0L if the file does not exist.
Note that you use currWD as working directory for your bat-file. You could try to do:
new File(currWD, fileName).length()
to make sure you look for the file in the right directory.
It probably has to do with executing the bat file from a command shell. What does the bat file do? Is it launching a program?
I'm guessing that the script calls or executes another program and returns which allows the shell to die. This in turn let's the java process continue while the process from the script continues executing asynchronously.
According to the Java API for Process, that's allowable which it most definitely should be (link java.lang.Process)
I credit this answer to aioobe and John. As John suggests, the external program started by the batch file spawns a process that seems to be running for a while (50-300 millisec) after the Java sub-process running the batch file has returned. I resolved the problem by introducing a pause (as suggested by aioobe) :
int exitValue = pr.waitFor();
try {Thread.currentThread().sleep(300);} catch (InterruptedException e) {e.printStackTrace();}
After the pause Java seems to be able to see the files created by the external program. Thanks again to both contributors who helped me resolve this issue!
If anyone finds a more elegant solution, please, feel welcome to post.