Friday, May 04, 2007

Getting more from streams in Bash

A handy trick in Bash is to split a stream to process it in more than one way without saving a temporary copy:

# Make 3 a copy of 1 (stdout)
exec 3>&1
result="$(command to generate stream \
    | tee /dev/fd/3 \
    | command to process stream)"
# Now work with $result
# The original stream also went to the console

The actual case I worked with this morning was a very simple demonstration:


exec 3>&1

echo -e "Bob is my friend.\nFred is my friend, too." \
    | tee /dev/fd/3 \
    | cut -f1 -d' ' >&2

Which simply prints:

Bob is my friend.
Fred is my friend.

to stdout and to stderr it prints:


That most excellent Erlang short

There is a short making the rounds, Erlang: The Movie. It is witty, indirect and informative. And subtly hilarious.

As programming language propaganda goes, this is highly effective: I really want to go out and try Erlang after watching. Nicely done.

Wednesday, May 02, 2007

Increasing log4j verbosity

To programmatically increase log4j verbosity, a simple code snippet does the trick:

final Logger rootLogger = Logger.getRootLogger();

        rootLogger.getLevel().toInt() + 1,

I use this to handle the -verbose command-line switch. Repeating the switch keeps increasing my program's verbosity.

Naturally there are wrinkles with a complex log4j configuration, but the idiom remains.

Tuesday, May 01, 2007

Subversion best practices, branching

A useful link on Subversion, Subversion Best Practices. Really nice are the links into the Red Bean book filling out each point.

What I am looking for at the moment is a good discussion on using Subversion to fork a project. I have internal libraries at work which are not ameniable to multiple teams working on them. My best option is to fork the code and merge back in fixes from the original.

This looks like a good start on this kind of branching. I like the example shell scripts for automating portions of the process.