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Java Forum / General / February 2007invoking a java application by name
So far I've always compiled my application with javac xxxx.java and invoked them with java xxxx.class I wonder if there could be a way to invoke the application directly. I know I could make an alias, alias xxxx 'java xxxx.class' and then invoke xxxx, but this is not what I mean I am thinking of a compilation like cc xxxx.c -o xxxx or f77 xxxx.f -o xxxx which generates a named executable xxxx (instead of a.out) Or something like shell or awk scripts, which I could write into files with the executable bit set (chmod +x) and prepend with things like #!/bin/csh -f #! /usr/bin/awk -f  Signature---------------------------------------------------------------------- nospam@mi.iasf.cnr.it is a newsreading account used by more persons to avoid unwanted spam. Any mail returning to this address will be rejected. Users can disclose their e-mail address in the article if they wish so. > So far I've always compiled my application with > javac xxxx.java > and invoked them with > java xxxx.class Probably just "java xxxx" (*not* .class) > Or something like shell or awk scripts, which I could write into files > with the executable bit set (chmod +x) and prepend with things like > #!/bin/csh -f > #! /usr/bin/awk -f Of course you can always write a script to launch the application: #!/bin/sh exec java xxxx $@ /gordon Signature[ don't email me support questions or followups ] g o r d o n + n e w s @ b a l d e r 1 3 . s e On Feb 23, 3:09 pm, LC's No-Spam Newsreading account <nos...@mi.iasf.cnr.it> wrote: > So far I've always compiled my application with > javac xxxx.java [quoted text clipped - 20 lines] > avoid unwanted spam. Any mail returning to this address will be rejected. > Users can disclose their e-mail address in the article if they wish so. Though I assume (sure basically) that the only way to run a java program is to invoke it through java command, I am surprised how do you able to run java program through java xxxx.class as it should be java xxxx (no .class!!!). IS tht a typo? :) > Or something like shell or awk scripts, which I could write into files > with the executable bit set (chmod +x) and prepend with things like > #!/bin/csh -f > #! /usr/bin/awk -f I'm not quite sure what you are looking for but the answer is probably: no, or at least not easily, and not using only the standard tools. But if you are looking for a way to use Java to write scripts, then you may want to look at something like BeanShell: http://www.beanshell.org/ in particular: http://www.beanshell.org/manual/execscripts.html#Executable_scripts_under_Unix -- chris > I'm not quite sure what you are looking for but the answer is > probably: no, or at least not easily, and not using only the standard > tools. > But if you are looking for a way to use Java to write scripts, then you may > want to look at something like BeanShell: http://www.beanshell.org/ I've saved the reference, but that's not what I was thinking of. More the reverse. Invoking an arbitrary java application by name without prepending the invocation of the java interpreter. Just "xxx" or "xxx.class" instead of "java xxx" (YES, 'java xxx.class' was a typo). One suggestion by Gordon Beaton was "Of course you can always write a script to launch the application:" #!/bin/sh exec java xxxx $@ Actually one can do it even with a one-liner script e.g. in our local environment #!/scisoft/bin/java myServer which saves a shell process. Exactly like having a file.awk executable and prepended with #!/bin/awk -f can invoke it. But this awk file will contain the code, the one-liner will just make reference to a compiled myServer.class. A shell alias (alias myServer 'javac myServer') would be a lighter solution. Still is unelegant to have (in principle) search one's path for all existing .class files and set up aliases for each one. It reminds me of the old VMS times when I used (at login) to search a path and set up a logical symbol (I believe was called so) for each program.EXE file in the path, to avoid invoking a compiled exeutable with "RUN program". I even had a sort of "rehash" command implied in every compilation. But I guess I won't have that many java executables around, mainly now while I'm testing alternatives Signature---------------------------------------------------------------------- nospam@mi.iasf.cnr.it is a newsreading account used by more persons to avoid unwanted spam. Any mail returning to this address will be rejected. Users can disclose their e-mail address in the article if they wish so. > Invoking an arbitrary java application by name without > prepending the invocation of the java interpreter. On Linux, you can use the binfmt misc support to make jarfiles and class files executable. I remember playing with this about 10 years ago but haven't thought about it since, and don't know what the current status is. A quick search came up with this: http://www.nirendra.net/cms/java/linux > One suggestion by Gordon Beaton was "Of course you can always write a > script to launch the application:" [quoted text clipped - 7 lines] > > which saves a shell process. There is no real difference here. By specifying "exec" the shell process only exists a short time; exec causes it to be replaced by the java process. /gordon Signature[ don't email me support questions or followups ] g o r d o n + n e w s @ b a l d e r 1 3 . s e > On Linux, you can use the binfmt misc support to make jarfiles and > class files executable. I remember playing with this about 10 years Thank you for letting me know about "binfmt". I was not aware of it, but looks quite interesting. > > #!/bin/sh > > exec java xxxx $@ > > #!/scisoft/bin/java myServer > There is no real difference here. By specifying "exec" the shell > process only exists a short time; exec causes it to be replaced by the > java process. Yes, I know what exec (and the execvp and alike library calls do), but my friend William of Ockham taught me that shells non sunt multiplicanda praeter necessitatem :-) Signature---------------------------------------------------------------------- nospam@mi.iasf.cnr.it is a newsreading account used by more persons to avoid unwanted spam. Any mail returning to this address will be rejected. Users can disclose their e-mail address in the article if they wish so. On Feb 23, 9:09 pm, LC's No-Spam Newsreading account <nos...@mi.iasf.cnr.it> wrote: .. > I wonder if there could be a way to invoke the application directly. I usually find it easier to double click a jar with manifest that names the main() class, or open the desktop shortcut/menu item that web start sets up. Note though, the first way might require special set-up on Linux systems (it is automatic in later Plug-Ins for Windows) while the second is really only suited to applications with a GUI. Andrew T. 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