Recording audio from mic and speakers from commandline

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Finally I found a way to achieve what I wanted, using the PulseAudio utility "pacmd".

This tutorial help me

$ pacmd list-sources|awk '/index:/ {print $0}; /name:/ {print $0}; /device\.description/ {print $0}'

Run above command to get the names of all the recording interfaces. Sample output is given below.

    index: 0
    name: <alsa_output.pci-0000_00_1b.0.analog-stereo.monitor>
        device.description = "Monitor of Built-in Audio Analog Stereo"
  * index: 1
    name: <alsa_input.pci-0000_00_1b.0.analog-stereo>
        device.description = "Built-in Audio Analog Stereo"

To record from my Speakers: use "Monitor of Built-in Audio Analog Stereo"

 $ ffmpeg -f pulse -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor -c:a libmp3lame output.mkv

To record from my Mic: use "Built-in Audio Analog Stereo"

 $ ffmpeg -f pulse -i alsa_input.pci-0000_00_1b.0.analog-stereo -c:a libmp3lame output.mkv