Archive for September, 2009
Can you spot Java Puzzler in this snippet?
Reading time: < 1 minute
I ran across this last week. It was marvelous when we saw what was happening, but entirely puzzling at first.
Boolean someFlag = complicatedLogicToFigureOutFlag(); Person person = new Person(someFlag);
Any signs for concern? How about if Person’s constructor is:
Person(boolean someFlag) { this.someFlag = someFlag; }
Any warning signs?
Will it compile?
Read more for the full puzzler.
How to do 3-way merges with Subversion and Kdiff3
Reading time: 4 – 7 minutes
I do not endorse branch based development. I prefer trunk based development. Specifically I like what my colleague Paul calls Branch By Abstraction, coined by Stacy Curl, and recently mentioned by Martin Fowler (All one time ThoughtWorkers, and 2 currently).
If you’re stuck with merging though, 3-way merges make it much easier. Doing it with subversion is easy. Instructions are for Linux.
- apt-get or yum install kdiff3.
- Edit your /etc/subversion/config and fin the line with diff3-cmd, set it to: diff3-cmd=/usr/local/bin/svndiff.sh
- Next, create the file /usr/local/bin/svndiff.sh. See below for the script you’ll want to enter in it.
Now when you get a merge conflict you will choose M and merge will open in kdiff3. On the left is the base revision, in the middle is your working copy, and on the right the incoming change. This is a little more to look at, but it is invaluable when dealing with merges. I wouldn’t go back to 2 way diff ever again.
#!/bin/bash
# tim/paul: this is a copy of the file located at http://www.yolinux.com/TUTORIALS/src/svndiffwrapper.txt
# modified to do a non-conflicting merge automatically. see #HERE#
# Return an errorcode of 0 on successful merge, 1 if unresolved conflicts
# remain in the result. Any other errorcode will be treated as fatal.
# Author: Michael Bradley
#NOTE: all output must be redirected to stderr with "1>&2" as all stdout output is written to the output file
VDIFF3="kdiff3"
DIFF3="diff3"
DIFF="kdiff3"
promptUser ()
{
read answer
case "${answer}" in
"M" )
echo "" 1>&2
echo "Attempting to merge ${baseFileName} with ${DIFF}" 1>&2
$VDIFF3 $older $mine $theirs --L1 $labelOlder --L2 $labelMine --L3 $labelTheirs -o $output 1>&2
bLoop=1
if [ -f $output ]; then
if [ -s $output ]; then
#output succesfully written
bLoop=0
fi
fi
if [ $bLoop = 0 ]; then
cat $output
rm -f $output
exit 0
else
echo "Merge failed, try again" 1>&2
fi
;;
"m" )
echo "" 1>&2
echo "Attempting to auto-merge ${baseFileName}" 1>&2
diff3 -L $labelMine -L $labelOlder -L $labelTheirs -Em $mine $older $theirs > $output
if [ $? = 1 ]; then
#Can't auto merge
rm -f $output
$VDIFF3 $older $mine $theirs --L1 $labelOlder --L2 $labelMine --L3 $labelTheirs -o $output --auto 1>&2
bLoop=1
if [ -f $output ]; then
if [ -s $output ]; then
#output succesfully written
bLoop=0
fi
fi
if [ $bLoop = 0 ]; then
cat $output
rm -f $output
exit 0
else
echo "Merge failed, try again" 1>&2
fi
else
#We can automerge, and we already did it
cat $output
rm -f $output
exit 0
fi
;;
"diff3" | "Diff3" | "DIFF3" )
echo "" 1>&2
echo "Diffing..." 1>&2
$VDIFF3 $older $mine $theirs --L1 $labelOlder --L2 $labelMine --L3 $labelTheirs 1>&2
;;
"diff" | "Diff" | "DIFF" )
echo "" 1>&2
echo "Diffing..." 1>&2
$DIFF $mine $theirs -L $labelMine -L $labelTheirs 1>&2
;;
"A" | "a" )
echo "" 1>&2
echo "Accepting remote version of file..." 1>&2
cat ${theirs}
exit 0
;;
"I" | "i" )
echo "" 1>&2
echo "Keeping local modifications..." 1>&2
cat ${mine}
exit 0
;;
"R" | "r" )
echo "" 1>&2
echo "Reverting to base..." 1>&2
cat ${older}
exit 0
;;
"D" | "d" )
echo "" 1>&2
echo "Runnig diff3..." 1>&2
diff3 -L $labelMine -L $labelOlder -L $labelTheirs -Em $mine $older $theirs
#Exit with return vaule of the diff3 (to write out files if necessary)
exit $?
;;
"S" | "s" )
echo "" 1>&2
echo "Saving for later..." 1>&2
cat ${mine}
#Exit with return vaule of 1 to force writting of files
exit 1
;;
"Fail" | "fail" | "FAIL" )
echo "" 1>&2
echo "Failing..." 1>&2
exit 2
;;
"H" | "h" )
echo "" 1>&2
echo "USAGE OPTIONS:" 1>&2
echo " [A]ccept Accept $labelTheirs and throw out local modifications" 1>&2
echo " [D]efault Use diff3 to merge files (same behavior as vanilla SVN)" 1>&2
echo " [Fail] Kills the command (not suggested)" 1>&2
echo " [H]elp Print this message" 1>&2
echo " [I]gnore Keep your locally modified version as is" 1>&2
echo " [M]erge Manually merge using ${VDIFF3}" 1>&2
echo " [m]erge Same as "M" but attempts to automerge if possible" 1>&2
echo " [R]evert Revert to base version (${labelOlder})" 1>&2
echo " [S]ave Same as 'I' but writes out rold, rnew, and rmine files to deal with later" 1>&2
echo " [diff] Type 'diff' to diff versions $labelMine and $labelTheirsthe before making a descision" 1>&2
echo " [diff3] Type 'diff3' to diff all three versions before making a descision" 1>&2
echo "" 1>&2
;;
* )
echo "'${answer}' is not an option, try again." 1>&2
;;
esac
}
if [ -z $2 ]
then
echo ERROR: This script expects to be called by subversion
exit 1
fi
if [ $2 = "-m" ]
then
#Setup vars
labelMine=${4}
labelOlder=${6}
labelTheirs=${8}
mine=${9}
older=${10}
theirs=${11}
output=${9}.svnDiff3TempOutput
baseFileName=`echo $mine | sed -e "s/.tmp$//"`
#HERE#
diff3 -L $labelMine -L $labelOlder -L $labelTheirs -Em $mine $older $theirs > $output
if [ $? = 1 ]; then
#Can't auto merge
#Prompt user for direction
while [ 1 ]
do
echo "" 1>&2
echo "${baseFileName} requires merging." 1>&2
echo "" 1>&2
echo "What would you like to do?" 1>&2
echo "[M]erge [A]ccept [I]gnore [R]evert [D]efault [H]elp" 1>&2
promptUser
done
else
#We can automerge, and we already did it
cat $output
rm -f $output
exit 0
fi
else
L="-L" #Argument option for left label
R="-L" #Argument option for right label
label1=$3 #Left label
label2=$5 #Right label
file1=$6 #Left file
file2=$7 #Right file
$DIFF $file1 $file2 $L "$label1" $L "$label2" &
#$DIFF $file1 $file2 &
#wait for the command to finish
wait
fi
exit 0Note: I also posted this to a gist on github: svndiff.sh.
Ruby Script to Organize Mp3’s based on ID3 Genre Tag
Reading time: 2 – 4 minutes
I had one gigantic directory of all my tagged and organized mp3 files. Problem is it was too big to use. This bloated my library and I have since not been able to fit my music on my laptop. I needed to manipulate mp3 files by genre and extract them out of this single directory to create smaller libraries. I spent all of about two minutes looking for a program to do this before deciding to write a script. Truthfully, it was worse: once upon a time I over-enthusiastically downloaded StepMania and 493 DDR games/songs. And then, I added all the songs into my music library. It’s a great party game, but not the kind of music I want to listen to.
Many implementations exist for reading ID3 tags. I first tried ruby-mp3info, however it didn’t read my custom genre (‘DDR’) so then I moved to id3lib-ruby which uses the c++ id3lib library.
This worked like a charm. I ran the script over all my directories and built up a list of the directories.
#!/usr/bin/env ruby # find_music.sh require "rubygems" require 'id3lib' require 'find' require 'set' ddr_files = [] ddr_dirs = Set.new search_dir = '~/media/music/music_categorized' Find.find(search_dir) do |file| next if file !~ /.*mp3$/ mp3 = ID3Lib::Tag.new(file) next if mp3.genre != 'DDR' ddr_dirs << File.dirname(file) ddr_files << file puts "%s, %s --> AT: %s" % [mp3.genre, mp3.album, file] end File.open('result-ddr-files.txt', 'w') do |f| f.write(ddr_files.join("\n")) end File.open('result-ddr-dirs.txt', 'w') do |f| ddr_dirs.each { |d| f.write("%s\n" % d)} end
Next I reviewed the two output files, then ran the file result-ddr-dirs.txt in as an argument into this next script. That removed almost a gig of music from my library.
#!/usr/bin/env ruby if (ARGV.length != 1) puts "Usage: #{__FILE__} input_file" exit(1) end destination="/home/jwolter/media/music/music_ddr_questionable_value/" File.foreach(ARGV[0]) do |line| next if line.strip == "" cmd = "mv \"#{line.strip}\" \"#{destination}\"" #puts cmd `#{cmd}` end
Bonus: In the process searching for this, I ran into the ID3 Tags RubyQuiz.
One of the nicest benefits of being a software engineer is I avoid doing boring manual tasks on my computer. Writing a script is more fun, and faster. I’ve got many scripts to automate file manipulation, online banking, and more. What bit of your automation scripts do you think is the most helpful?
