Handy commands

By Sachin
October 9, 2016

List of commands for day-to-day use

(Updated on Mar 04, 2017)

Generic

  • SOCKS proxy using SSH

    ssh -N -D 1080 user@server
    

    -N: Do not execute remote commands.

    -D: [bind address:]port. Port in above example.

  • wget a website

    wget -rkp -l5 -np -nH -cut-dirs=1 https://example.com
    

    -rkp: recursive, make link suitable for local viewing, download all files needed to properly view the page.

    -l5: recursively download 5 links away form the original page.

    -n: retrieve files below parent directory.

    -H: Span across hosts when doing recursive retrieving.

  • Capture screenshot

    import -window root screenshot.png
    

PDF

  • Reduce PDF size

    gs -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -sOutputFile=new_file.pdf original_file.pdf
    
  • Unlock PDF file

    gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=unencrypted.pdf -c .setpdfwrite -f encrypted.pdf
    

ffmpeg

  • Rotate video

    # Using mplayer(watch rotated video)
    mplayer -vf-add rotate=1 sample.mp4
    
    # Using ffmpeg
    ffmpeg -i infile.mp4 -strict -2 -vf "transpose=1" outfile.mp4
    
  • Convert 3GP to MP4

    ffmpeg -i VID_0050.3gp -strict -2 -q:a 0 -ab 64k -ar 44100 VID_0050.mp4
    
  • FLV to MP4

    ffmpeg -i input.flv -qscale 1 -ar 22050 output.mp4
    
  • Extract audio(MP3) from MP4 video

    ffmpeg -i video.mp4 -f mp3 -ab 192000 -vn music.mp3
    

    or specify codec to use libmp3lame in this case.

    ffmpeg -i video.mp4 -f mp3 -codec:a libmp3lame -ab 320000 -vn music.mp3
    

    -i: input file

    -f mp3: file format should be MP3

    -ab 192000: audio should be encoded at 192Kbps. 320000 for 320Kbps

    -vn: don’t want video

  • Cut video by time interval

    Cut video starting from 19 min 49 seconds up to 04 mins 18 seconds.

    ffmpeg -y -i Video.mp4 -qscale 1 -ss 00:19:49.0 -t 00:04:18.0 -acodec copy -vcodec copy output.mp4
    

    Note: -sameq was removed in recent version of ffmpeg

  • Use mplayer to extract audio(MP3)

    mplayer -dumpaudio movie.flv -dumpfile movie_audio_track.mp3
    
  • Reduce resolution

    ffmpeg -i Birdman.mp4 -strict -2  -s 720x480 birdman.mp4
    

Image manipulation

  • Resize image 50% of its original size

    convert dragon.gif -resize 50% half_dragon.gif
    
  • Control compression level of an image

    convert input.png -quality 75 output.jpg