Problem about Executing Unix command in java

Question

Hi All,
Does someone know why the following codes didn't run correctly?
String cmd = "tar cvf 123.tar *.*";
try
Runtime rt = Runtime.getRuntime();
rt.exec(cmd);
catch (Exception ex)
ex.printStackTrace();
Thanks.

Answer 1

Because "*" is interpreted by the shell--bash, zsh, ksh, sh, csh, tcsh...
The shell turns *.java into a.java b.java. The tar program never sees the *.
You don't typcially have these shells when you invoke a command like that, so the tar program sees the * you pass and takes is as a file name. It's like adding quotes or a backslash in a terminal window:$ tar cvf foo.tar '*.java' So either use the File and FileFilter classes to get a list of the files you want to pass and send that to Runtime.exec, or Runtime.exec a shell and pass tar as its command.
For bash, I think what you'd pass to Runtime.exec would be something like sh -c tar cvf foo.tar *.java but check the man page for your shell to find out the details of how to invoke it in non-interactive mode and pass it a command.