• Imagemagick is useful for me, because sometimes I deal with images in batch, like stripping exif data, combining several images into one etc. Yes, Photoshop can do these, but I don't want to spend time launching Photoshop.
  • qpdf. Really fast to merge pdf files into one. I could do this with LaTeX with the pdfpages package and I even made a LaTeX file just for doing that.
  • ddjvu. Converts djvu files to pdf. This is useful because there are loads of pdf viewers on tablet but it seems there is no free djvu viewer there. I realised that there is downside that the generated pdf is not searchable.
  • find. Batch process files. I am just so bad with the various switches. For me, the search criteria, -iname and -type, are the most useful and then I execute commands on the search result by using -execdir. It is just ugly to need to write command with {} being the current file name and to need to conclude the command by \;.
  • org-mode + emacs. Keeps all my notes and it is easy to search through notes. My useful bash one-liners are stored there.
  • fish. I guess I won't look up the many bash tricks in my org files any more.
  • mosh. No more accidentally dropped ssh sessions. However it could be bad to forget to log off.
  • youtube-dl. Command line tool to download Youtube videos so that I can watch those without Internet. Actually it works for so many sites in addition to Youtube.
  • qrencode. Sometimes I want to continue reading a web page on iPad. It generates a QR code for the url and then I use my phone to scan it. I wrote a small fish function to encapsulate the parameters I often use as well as show the picture on screen immediately. No third party messaging service involved. No emailing to self. No Firefox syncing.