linux - Bash 19 个字符无缘无故消失

Question

我试图制作一个批处理脚本来压缩我的音频文件，但我遇到了一个非常奇怪的问题。

这是我的代码:

#!/bin/bash

qscale=$1
input=$2
output=$3
inputSize=$((${#input}+1))

find "$input" -type f -name "*.flac" -print0 | while read -d $'\0' a
do
    path=${a:inputSize}
    echo "Working on $path"
#    ffmpeg -i "$a" -qscale:a $qscale "$output/${path[@]/%flac/mp3}" &>/dev/null
done

这是一个结果示例:

Working on 09 - Groove #2 (instrumental studio outtake).flac
Working on 07 - Blues for Allah Sand Castles and Glass Camels Unusual Occurrences in the Desert.flac
Working on 12 - Proto 18 Proper (instrumental studio outtake).flac
Working on 04 - The Music Never Stopped.flac
Working on 13 - Hollywood Cantana (studio outtake).flac
...

如果我取消注释 ffmpeg 行，这是同一文件夹的结果:

Working on 09 - Groove #2 (instrumental studio outtake).flac
Working on h Sand Castles and Glass Camels Unusual Occurrences in the Desert.flac
Working on 12 - Proto 18 Proper (instrumental studio outtake).flac
Working on r Stopped.flac
Working on 13 - Hollywood Cantana (studio outtake).flac
...

两个文件中的一个文件错过了第 19 个第一个字符!我不知道为什么。

Answer 1

取消注释 ffmpeg 行并运行 shellcheck在它上面报告:

Line 12:
    ffmpeg -i "$a" -qscale:a $qscale "$output/${path[@]/%flac/mp3}" &>/dev/null
    ^-- SC2095: Add < /dev/null to prevent ffmpeg from swallowing stdin.

再试一次

ffmpeg -i "$a" -qscale:a $qscale "$output/${path[@]/%flac/mp3}" &>/dev/null < /dev/null

ffmpeg 以及 ssh 和 mplayer 因从 while read 循环中窃取标准输入而臭名昭著。