Bash Script Parsing Argument not working correctly

Question

i have the following bash script (taken from FFmpeg)

#!/bin/bash ################################################################################ # # Script name: MultiMedia Concat Script (mmcat) # Author: burek ([email protected]) # License: GNU/GPL, see http://www.gnu.org/copyleft/gpl.html # Date: 2012-07-14 # # This script concatenates (joins, merges) several audio/video inputs into one # final output (just like as if all the inputs were played in a playlist, one # after another). # # All input files must have at least one audio and at least one video stream. # If not, you can easily add audio silence, using FFmpeg. Just search the # internet for "ffmpeg add silence". # # The script makes use of FFmpeg tool (www.ffmpeg.org) and is free for use under # the GPL license. The inspiration for this script came from this FAQ item: # http://ffmpeg.org/faq.html#How-can-I-join-video-files_003f # # If you find any bugs, please send me an e-mail so I can fix it. # ################################################################################ # # General syntax: mmcat <input1> <input2> <input3> ... <output> # # For example: mmcat file1.flv file2.flv output.flv # would create "output.flv" out of "file1.flv" and "file2.flv". # ################################################################################ # change this to what you need !!! EXTRA_OPTIONS=${@:2:1} ################################################################################ # # NO NEED TO TOUCH ANYTHING AFTER THIS LINE! # ################################################################################ # the version of the script VERSION=1.3 # location of temp folder TMP=${@:1:1} rm -rf $TMP mkdir $TMP ################################################################################ echo "MultiMedia Concat Script v$VERSION (mmcat) - A script to concatenate multiple multimedia files." echo "Based on FFmpeg - www.ffmpeg.org" echo "Don't forget to edit this script and change EXTRA_OPTIONS" echo "" ################################################################################ # syntax check (has to have at least 3 params: infile1, infile2, outfile ################################################################################ if [ -z $3 ]; then echo "Syntax: $0 <input1> <input2> <input3> ... <output>" exit 1 fi ################################################################################ # get all the command line parameters, except for the last one, which is output ################################################################################ # $first - first parameter # $last - last parameter (output file) # $inputs - all the inputs, except the first input, because 1st input is # handled separately ################################################################################ first=${@:3:1} last=${@:$#:1} len=$(($#-4)) inputs=${@:4:$len} # remove all previous tmp fifos (if exist) rm -f $TMP/mcs_* ################################################################################ # decode first input differently, because the video header does not have to be # kept for each video input, only the header from the first video is needed ################################################################################ mkfifo $TMP/mcs_a1 $TMP/mcs_v1 ffmpeg -y -i "$first" -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 $TMP/mcs_a1 2>/dev/null </dev/null & ffmpeg -y -i "$first" -an -f yuv4mpegpipe -vcodec rawvideo $TMP/mcs_v1 2>/dev/null </dev/null & # if you need to log the output of decoding processes (usually not necessary) # then replace the "2>/dev/null" in 2 lines above with your log file names, like this: #ffmpeg -y -i "$first" -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 $TMP/mcs_a1 2>$TMP/log.a.1 </dev/null & #ffmpeg -y -i "$first" -an -f yuv4mpegpipe -vcodec rawvideo $TMP/mcs_v1 2>$TMP/log.v.1 </dev/null & ################################################################################ # decode all the other inputs, remove first line of video (header) with tail # $all_a and $all_v are lists of all a/v fifos, to be used by "cat" later on ################################################################################ all_a=$TMP/mcs_a1 all_v=$TMP/mcs_v1 i=2 for f in $inputs do mkfifo $TMP/mcs_a$i $TMP/mcs_v$i ffmpeg -y -i "$f" -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 $TMP/mcs_a$i 2>/dev/null </dev/null & { ffmpeg -y -i "$f" -an -f yuv4mpegpipe -vcodec rawvideo - 2>/dev/null </dev/null | tail -n +2 > $TMP/mcs_v$i ; } & # if you need to log the output of decoding processes (usually not necessary) # then replace the "2>/dev/null" in 2 lines above with your log file names, like this: #ffmpeg -y -i "$f" -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 $TMP/mcs_a$i 2>$TMP/log.a.$i </dev/null & #{ ffmpeg -y -i $f -an -f yuv4mpegpipe -vcodec rawvideo - 2>$TMP/log.v.$i </dev/null | tail -n +2 > $TMP/mcs_v$i ; } & all_a="$all_a $TMP/mcs_a$i" all_v="$all_v $TMP/mcs_v$i" let i++ done ################################################################################ # concatenate all raw audio/video inputs into one audio/video ################################################################################ mkfifo $TMP/mcs_a_all mkfifo $TMP/mcs_v_all cat $all_a > $TMP/mcs_a_all & cat $all_v > $TMP/mcs_v_all & ################################################################################ # finally, encode the raw concatenated audio/video into something useful ################################################################################ ffmpeg -y -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i $TMP/mcs_a_all \ -y -f yuv4mpegpipe -vcodec rawvideo -i $TMP/mcs_v_all \ $EXTRA_OPTIONS \ $last ################################################################################ # remove all fifos ################################################################################ rm -f $TMP/mcs_* 

The above scripts takes arguments like this

bash script.sh tmp_folder video1 video2 video3 video4 ... output 

Its working fine, however it doesnt read correctly the arguments when they have spaces. For example if i have a video located in "/tmp/my video.avi" it will fail to read it properly and thinks its different argument.

The problem is in these lines

first=${@:3:1} last=${@:$#:1} len=$(($#-4)) inputs=${@:4:$len} 

Please note that you will see inside the scripts that video2 video3 and video4 are being processed seperate than video1.

Answer 1

I guess the (or one if there are many) problem is this line:

inputs=${@:4:$len} 

If $len is bigger than 1 then this converts an array slice into a string and there the word splitting problem arises.

possible solution

If should work if the above line is changed to

inputs=("${@:4:$len}") 

and this

for f in $inputs 

to

for f in "${inputs[@]}" 

Answer 2

You have to set the following code before any working files in your script:

SAVEIFS=$IFS IFS=$(echo -en "\n\b") 

Then when you want to exit from your script, you have to do it:

$IFS=$SAVEIFS