what regex expression replaces file extension using bash script

jdavis2 · 01-13-2010, 07:52 PM

What I was trying to ask is will anyone help me to complete a bash script that will take filename from the command line then do the conversion that I have asked it to do in the script and also assign a new extension of my choice that I will include in the script as in the following:

convert_this file.mp4

then the script will process and return a result with a new extension, sort of like this:

file.avi

What I am doing now is entering the comand like this:

convert_this file.mp4 file.avi using the following script.

ffmpeg -i $1 -r 20 -vcodec mpeg4 -vtag DX50 -b 512k -acodec mp3 -ab 128k -bufsize 4m -qmax 51 -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -ar 44100 -g 300 -s 224x176 -aspect 4:3 -ac 2 -y $2

kbp · 01-13-2010, 09:30 PM

Code:

FILE=$1

FULLNAME=$(basename $FILE)
EXT=$(echo $FULLNAME | sed 's/^.*\.//')
NAME=$(basename $FILE .${EXT})
NEWEXT=mpg
NEWNAME=${NAME}.${NEWEXT}

echo "Extension: $EXT"
echo "Name: $NAME"
echo "Newname: $NEWNAME"

cheers

GooseYArd · 01-13-2010, 09:42 PM

courtesy of alunduil

Code:

filename="something.extension"
basename=${filename%.*}
extension=${filename##*.}

jdavis2 · 01-13-2010, 10:40 PM

Quote:

Originally Posted by kbp

Code:

FILE=$1

FULLNAME=$(basename $FILE)
EXT=$(echo $FULLNAME | sed 's/^.*\.//')
NAME=$(basename $FILE .${EXT})
NEWEXT=mpg
NEWNAME=${NAME}.${NEWEXT}

echo "Extension: $EXT"
echo "Name: $NAME"
echo "Newname: $NEWNAME"

cheers

Here is my final script and it works like a charm. I even managed to understand most of what happened.

#!/bin/sh

FILE=$1

FULLNAME=$(basename $FILE)
EXT=$(echo $FULLNAME | sed 's/^.*\.//')
NAME=$(basename $FILE .${EXT})
NEWEXT=avi
NEWNAME=${NAME}.${NEWEXT}

ffmpeg -i $FILE -r 20 -vcodec mpeg4 -vtag DX50 -b 512k -acodec mp3 -ab 128k -bufsize 4m -qmax 51 -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -ar 44100 -g 300 -s 224x176 -aspect 4:3 -ac 2 -y $NEWNAME

syg00 · 01-14-2010, 12:08 AM

There is a lot of redundant processing there - doesn't matter for 1 file, but could in a decent sized loop. As per GooseYArd, what about this ?

Code:

#!/bin/sh

ffmpeg -i $1 -r 20 -vcodec mpeg4 -vtag DX50 -b 512k -acodec mp3 -ab 128k -bufsize 4m -qmax 51 -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -ar 44100 -g 300 -s 224x176 -aspect 4:3 -ac 2 -y ${1%.*}.avi

jdavis2 · 01-14-2010, 05:39 PM

Quote:

Originally Posted by syg00

There is a lot of redundant processing there - doesn't matter for 1 file, but could in a decent sized loop. As per GooseYArd, what about this ?

Code:

#!/bin/sh

ffmpeg -i $1 -r 20 -vcodec mpeg4 -vtag DX50 -b 512k -acodec mp3 -ab 128k -bufsize 4m -qmax 51 -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -ar 44100 -g 300 -s 224x176 -aspect 4:3 -ac 2 -y ${1%.*}.avi

I wasn't able to following what GooseYArd posted before but now I understand. Thanks for pointing out how simple this could be if you know the rules.