bash script error let: syntax error in expression ( symbol error is << 0:6 >> )

Question

I don't have a good level in bash but with some knowledge I made this script which allows me to compress a serie I ripped from a Bluray :

#!/bin/bash

files=(*.mkv)
AUDIOCOUNTER=0
AUDIOFRCOUNTER=0
# Find out which tracks contain the audio
mkvmerge --identify --identification-format json "${files[0]}" | jq '.tracks[] | select(.type=="audio").properties.language' | ( while read audio_tracks
do
  # Grep the number of audio tracks
  if [[ "$audio_tracks" = "fre" ]];then
    let AUDIOFRCOUNTER++
  fi
  let AUDIOCOUNTER++
done
if [[ "$AUDIOCOUNTER" -gt 1 && "$AUDIOFRCOUNTER" -gt 0 ]];then
  read -p 'encode MULTi ? (y/n) : ' multi
fi)

read -p 'CRF cible : ' crf
read -p 'Qualité audio : ' audioquality
read -p 'Convertir en stereo ? (y/n) : ' audiostereo

for FILE in *.mkv
do
  file=${FILE%.*}
  if [ $multi = "y" ]
  then
    if [ $audiostereo = "y" ]
    then
      ffmpeg -i "$file.mkv" -vn -c:a libfdk_aac -profile:a aac_he_v2 -vbr $audioquality -map a -map -m:language:fre -af "pan=stereo|FL < 1.0*FL + 0.707*FC + 0.707*BL|FR < 1.0*FR + 0.707*FC + 0.707*BR" "encoded/$file.fr.m4a"
      ffmpeg -i "$file.mkv" -vn -c:a libfdk_aac -profile:a aac_he_v2 -vbr $audioquality -map a -map -m:language:eng -af "pan=stereo|FL < 1.0*FL + 0.707*FC + 0.707*BL|FR < 1.0*FR + 0.707*FC + 0.707*BR" "encoded/$file.en.m4a"
    else 
      ffmpeg -i "$file.mkv" -vn -c:a libfdk_aac -profile:a aac_he_v2 -vbr $audioquality -map a -map -m:language:fre "encoded/$file.fr.m4a"
      ffmpeg -i "$file.mkv" -vn -c:a libfdk_aac -profile:a aac_he_v2 -vbr $audioquality -map a -map -m:language:eng "encoded/$file.en.m4a"
    fi
  else
    if [ $audiostereo = "y" ]
    then
      ffmpeg -i "$file.mkv" -vn -c:a libfdk_aac -profile:a aac_he_v2 -vbr $audioquality -af "pan=stereo|FL < 1.0*FL + 0.707*FC + 0.707*BL|FR < 1.0*FR + 0.707*FC + 0.707*BR" "encoded/$file.en.m4a"
    else 
      ffmpeg -i "$file.mkv" -vn -c:a libfdk_aac -profile:a aac_he_v2 -vbr $audioquality "encoded/$file.en.m4a"
    fi
  fi


  subtitle_param=""
  mkvmerge --identify --identification-format json "$file.mkv" | jq '.tracks[] | select(.codec=="SubRip/SRT" and (.properties.language=="fre" or .properties.language=="eng")).properties.number' | ( while read subtitle_track_number
  do
    echo "$subtitle_track_number"
    let subtitle_param+="-map 0:$subtitle_track_number "    
    echo "$subtitle_param"
  done)

  echo "subtitle param : $subtitle_param"

  read -p 'Continue ? : '

  if [ $subtitle_param = "" ]
  then
    ffmpeg -i "$file.mkv" -map 0:v -c:v libx265 -crf $crf -preset  medium -pix_fmt yuv420p -an "encoded/$file.mkv"
  else
    ffmpeg -i "$file.mkv" -map 0:v -c:v libx265 -crf $crf -preset  medium -pix_fmt yuv420p -map -0:a "$subtitle_param" -c:s copy "encoded/$file.mkv"
  fi
  
  if [ $multi = "y" ]
  then
    mkvmerge -o "remuxed/$file.mkv" "encoded/$file.mkv" --language 0:fre "encoded/$file.fr.m4a" --language 0:eng "encoded/$file.en.m4a"
    mkvpropedit "remuxed/$file.mkv" --tags all:"" --delete title --edit track:a1 --set flag-default=1 --delete name --edit track:a2 --set flag-default=0 --delete name --edit track:s1 --delete name --set flag-default=1 --set flag-forced=1 --edit track:s2 --delete name --set flag-default=0
    rm -f "encoded/$file-fr.m4a"
  else
    mkvmerge -o "remuxed/$file.mkv" --no-subtitles "encoded/$file.mkv" --language 0:eng "encoded/$file.en.m4a"
    mkvpropedit "remuxed/$file.mkv" --tags all:"" --delete title --edit track:a1 --set flag-default=1 --delete name
  fi 
  
  rm -f "encoded/$file.mkv"  
  rm -f "encoded/$file.en.m4a"
done

Everythings works until this block of code :

  subtitle_param=""
  mkvmerge --identify --identification-format json "$file.mkv" | jq '.tracks[] | select(.codec=="SubRip/SRT" and (.properties.language=="fre" or .properties.language=="eng")).properties.number' | ( while read subtitle_track_number
  do
    echo "$subtitle_track_number"
    let subtitle_param+="-map 0:$subtitle_track_number "    
    echo "$subtitle_param"
  done)

I'm detecting language using the infos returned by mkvmerge in json using another shell instance, I need to get the track number of all subtitles that matche Fr or English language, so I use let to acces the subtitle_param outside of this shell instance in the main instance. But it throws the error :

let: syntax error in expression ( symbol error is << 0:6 >> )

Any suggestion ? :)

choroba · Accepted Answer · 2021-02-09 16:08:13Z

1

let evaluates arithmetic expressions. When you want to concatenate strings, you don't need arithmetic expressions, so drop the let.

subtitle_param+="-map 0:$subtitle_track_number "

answered Feb 9, 2021 at 16:08

choroba

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8 Comments

Victor Lebkowski Over a year ago

That's what I did before but I can't access it outside the while read loop

choroba Over a year ago

Because you change the variable in a subshell. Subshell environment doesn't propagate back to the parent shell.

Victor Lebkowski Over a year ago

There's no way to propagate to the parent shell ? Or do you know another way to read the json and get the infos that I want ?

choroba Over a year ago

The common trick is to use process substitution: while read ... done < <(generate the data here).

Victor Lebkowski Over a year ago

by "generate the data here" you mean I have to put a command to store the output in a var ? I can't just directly put it in var ? Like : while read ... done < <($my_var)

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