自动合并哔哩哔哩官方客户端下载的flv格式分段视频。直接合并，不重编码。放到可执行目录下后，cd到分段视频所在目录，执行即可。如需要可指定保存文件名。

concat_bilibili_video.sh

#! /bin/bash

# ###########
#
# put the file at any executable path, cd to the video path, and do the cmd below:
#
# cmd format: bilibili.sh filename [1]
#
# filename is the output name of the video/audio
# if the optional arg is 1, an audio file will be extractd from the generated video file
#
# ###########

# get output file name
name=output
if [ -n "$1" ];then
	name=$1
fi

v="${name}.mkv"

# rm filelist.txt to prevent repeation
if [ -f filelist.txt ];then
	rm filelist.txt
fi

# generate concat file
for flv in `ls -tr *.flv`
do
	echo $flv
	echo "file '"$flv"'" >> filelist.txt
done

# concat the video
if [ ! -n "$v" ];then
	ffmpeg -f concat -i filelist.txt -c copy "${name}.mkv"
fi

# extract audio
if [ -n "$2" ] && [ "$2" == "1" ];then
	ffmpeg -i "$v" -vn -y -acodec copy "${name}.aac"
fi