Concatenate or Convert audio or video files

In Ubuntu Linux, install the utility ffmpeg:
sudo  apt-get  install  ffmpeg

Say you want to convert all the mp3 files in a directory to a single file called output.mp3. Then do the following. 
1. cd  to the directory
2. ls  *.mp3  >  list.txt
3. ffmpeg  -f  concat  -i list.txt  -c  copy  output.mp3