It is useful to have different versions of the JVM installed, for a number of reasons:

• Different optimisation features from different JVM implementations
• Different language features from different JVM versions
• Java classes compiled with “Tiger” won't run in “Mantis”…

It is also useful to be able to quickly switch between installed JREs/JDKs depending on the task at hand.

If I'm hacking in Linux, the JPackage project provides a much nicer solution to this problem, and the Linux distro' I'm using (SUSE 10.0) uses JPackage. It'd be nice if there was an update-alternatives for Cygwin, but since there isn't I've come up with this hack.

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On the 32-bit Windows platform, JVM programs can only ever use up to about 1.5–1.6 GiB of memory in RAM per Java VM process. Allocating a heap size greater than this amount does not work. What's going on?

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When you first install cygwin and run bash, it'll usually display this error message:

Your group is currently "mkpasswd".  This indicates that
the /etc/passwd (and possibly /etc/group) files should be rebuilt.
See the man pages for mkpasswd and mkgroup then, for example, run
mkpasswd -l [-d] > /etc/passwd
mkgroup  -l [-d] > /etc/group
Note that the -d switch is necessary for domain users.

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In vanila SuSE 10.0, safely removing a USB frob can be a trial for non-root users. It's a shame, but I've found a fix that I'm 95% happy with.

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I finally got fed up enough with Courier New to start searching for a legible, monospace font to use in jEdit. In Emacs, I'm particularly fond of the standard X font "misc-fixed" (though it's a little tough to tell appart O and 0 still). But for jEdit, the Java monospace font seems to map to Courier New in Windows, and to some God-awful font on Linux.

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I've been playing with customising jEdit a little bit, and decided to have a go at writing some simple date insertion macros. These perform the same work as some old elisp functions I wrote years ago in Emacs, to insert date/time stamps in various formats. In my .emacs file, I bind these functions to short-cut keys, and then use them for updating Changelogs in code and in offline journal entries.

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This post was originally published at sinewalker.wordpress.com on 1 May 2006.

I posted this reply to an Ask Slashdot:  Do Kids still program? I found myself commenting all over that thread… it must be close to my heart :-) Reproducing here, and exploring a little further.

Many of the observations made on Slashdot are right. I wonder what it is that drives me to hack, that is missing from what is covered? Why do I like to hack, and why would it be passed over by kids these days? Or would it?

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This post was originally published at sinewalker.wordpress.com on 18 April 2006.

While I'm on the subject of Cygwin hacking, I discovered this man-page about the Cygwin X server: type man XWinrc and read about how you can hack your systray icon to include a little launcher menu for you favorite X clients 8)

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This post was originally published at sinewalker.wordpress.com on 18 April 2006.

I don't know why I haven't ever got around to this, but here—finally—is a hack to have Cygwin only ever start one instance of emacs (especially important in cygwin, because Win32 does not appear to share program texts between processes… )

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This post was originally published at sinewalker.wordpress.com on 4 April 2006.

I'm sure this observation has been made elsewhere, but I can't find reference to it online.

Have you ever noticed the prolific use of mystical/fantastical words in computer jargon? I'm sure there is a significance, or at least a tongue-in-cheek pointing to the wizardly ways of early and contemporary computer experts. It is funny I suppose, and when you look at how wide-spread it is, it may be revealing of the hacker psych.

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