Shell Scripting

One thing that Linux and its brethren have always done well is shell scripting. Windows users are unfortunately missing out on this wonderful tool.

Oh, sure, Windows has DOS .bat and .cmd files, PowerShell scripts, and VBScript .vbs files. That's three different scripting languages to learn, if you want to work with other people (since in a group, someone else is bound to prefer something different than you). Plus, I have an intense dislike of VBScript, mainly for reasons like this:

Const OverwriteExisting = True Set objFSO = CreateObject("Scripting.FileSystemObject") objFSO.CopyFile "C:\file1" , "C:\file2", OverwriteExisting

Three lines to copy a file? Honestly? Anyway, I digress.

Shell scripting may not always be clear, but it does provide powerful tools for doing tasks that would otherwise take forever. Here are a few examples that may help with your media collection:

Rename with Lowercase Extensions

This will rename all files in the current directory and all subdirectories to have lower-case file extensions. It also demonstrates how you may get around the spaces-in-filenames issue that plagues most script writers:

find . -type f | while read name ; do # Get the directory name dname=`dirname "$name"`; # Get the file extension, as it is right now fext=`echo "$name" | sed -e "s/.*\\.\(.*\)/\\1/"`; # Get the file name, without the directory or extension fname=`basename "$name" ".$fext"`; # Make the extension lower-case fext=`echo "$fext" | tr [A-Z] [a-z]`; # Construct the new file name newname=$dname/$fname.$fext; # Rename the old file to the new # The -v option will print each move to the screen mv -v "$name" "$newname" done

Convert All Files to AVI

Here is one example that I use regularly at home. It takes all non-AVI files in this and all subdirectories and makes them into 2-pass encoded XviD AVIs using MEncoder. My wife and I own a DVD player that plays DivX/XviD files, so this makes any videos we may acquire playable on it:

# First, here are some standard options to MEncoder # Use Lame for MP3 encoding, average bitrate of 128 kbps audioOpts="-oac mp3lame -lameopts abr:br=128" # Use XviD for video encoding, bitrate of 750 kbps video1Opts="-ovc xvid -xvidencopts pass=1:bitrate=750" video2Opts="-ovc xvid -xvidencopts pass=2:bitrate=750" find . -type f | while read name ; do # Get the directory name dname=`dirname "$name"`; # Get the file extension, as it is right now fext=`echo "$name" | sed -e "s/.*\\.\(.*\)/\\1/"`; # If the file extension is .avi, no need to do anything if [ "`echo $fext | tr [A-Z] [a-z]`" = "avi" ] ; then echo "*** Skipping '$name', it is an AVI file ***" continue fi # Get the file name, without the directory or extension fname=`basename "$name" ".$fext"`; # Construct the new file name newname=$dname/$fname.avi; echo "*** Converting '$name' to '$newname' ***" # Create a directory to hold temporary data # The '$$' variable expands to the Process ID of # this shell program instance, very useful for # temporary file/directory names mkdir $$ cd $$ # Execute the first pass of mencoder # This generates a log file used by the second pass # That log file is why it needs its own directory # The '&&' at the end will only let the next mencoder # command execute if this one succeeds mencoder "../$name" $audioOpts $video1Opts -o /dev/null && # Execute the second pass of mencoder mencoder "../$name" $audioOpts $video2Opts -o "../$newname" # Go back to the starting directory and clean up cd .. rm -rf $$ done

I hope these are useful. Check back again for other scripting tips.