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Comment on Is there a self-hosted project that does base64 url decoding in a privacy respecting fashion?

The / character isn’t a part of the base64 encoding. In fact, only one part of the URL looks like base64. No plain base64 tool (whether via CLI, self-hosted, or otherwise) will be able to decode an entire URL like that. You’ll first need to parse the URL to isolate the base64 part. This is literally solved with a single line of bash:

echo "https://link.sfchronicle.com/external/41488169.38548/aHR0cHM6Ly93d3cuaG90ZG9nYmlsbHMuY29tL2hhbWJ1cmdlci1tb2xkcy9idXJnZXItZG9nLW1vbGQ_c2lkPTY4MTNkMTljYzM0ZWJjZTE4NDA1ZGVjYSZzcz1QJnN0X3JpZD1udWxsJnV0bV9zb3VyY2U9bmV3c2xldHRlciZ1dG1fbWVkaXVtPWVtYWlsJnV0bV90ZXJtPWJyaWVmaW5nJnV0bV9jYW1wYWlnbj1zZmNfYml0ZWN1cmlvdXM/6813d19cc34ebce18405decaB7ef84e41" | cut -d/ -f6 | base64 -d

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ReedReads@lemmy.zip ⁨19⁩ ⁨hours⁩ ago
Thank you for this

You know more than I do re: bash. Where can I learn what | cut -d/ -f6 | means? I assume the cut is the parsing? But maybe that is wrong? Would love to learn how to learn this.
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- krnl386@lemmy.ca ⁨12⁩ ⁨hours⁩ ago
  Try explainshell.com - you can paste in any oneliner and the site will parse it and explain each part.
  
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  - Enoril@jlai.lu ⁨5⁩ ⁨hours⁩ ago
    Really nice! Thanks for sharing this
    
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- 30p87@feddit.org ⁨16⁩ ⁨hours⁩ ago
  cut --help and man cut can teach you more than anyone here.
  
  But: “|” takes the output of the former command, and uses it as input for the latter. So it’s like copying the output of “echo […]”, executing “cut -d ‘/’ -f 6”, and pasting it into that. Then copy the output of “cut”, execute “base64 -d” and paste it there. Except the pipe (“|”) automates that on one line.
  
  And yes, cut takes a string (so a list of characters, for example the url), split’s it at what -d specifies (eg. cut -d ‘/’ splits at “/”), so it now internally has a list of strings, “https:”, “”, “link.sfchronicle.com”, “external”, 41488169.38548", “aHR0cHM6Ly93d3cuaG90ZG9nYmlsbHMuY29tL2hhbWJ1cmdlci1tb2xkcy9idXJnZXItZG9nLW1vbGQ_c2lkPTY4MTNkMTljYzM0ZWJjZTE4NDA1ZGVjYSZzcz1QJnN0X3JpZD1udWxsJnV0bV9zb3VyY2U9bmV3c2xldHRlciZ1dG1fbWVkaXVtPWVtYWlsJnV0bV90ZXJtPWJyaWVmaW5nJnV0bV9jYW1wYWlnbj1zZmNfYml0ZWN1cmlvdXM” and “6813d19cc34ebce18405decaB7ef84e41”, and from that list outputs whatever is specified by -f (so eg. -f 6 means the 6th of those strings. And -f 2-3 means the 2nd to 3rd string. And -5 means everything up to and including the fifth, and 3- means everything after and including the third).
  
  But all of that is explained better in the manpage (man cut). And the best way to learn is to just fuck around. So echo “t es t str i n g, 1” | cut … and try various arguments.
  
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- feedorimid@lemmynsfw.com ⁨19⁩ ⁨hours⁩ ago
  Cut into fields based on the delimiter (// in this case). The “-f6” selects which field you want.
  
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- ccryx@discuss.tchncs.de ⁨14⁩ ⁨hours⁩ ago
  You can use man cut to read a program’s manual page. Appending –help (without any other arguments will often produce at least a short description of the program and list the available options.
  
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