Using `cal` and plain text to track things, Part II

Back in September, I posted about using the output of cal and plain text to track things. Here is the example of that format I listed in the post:

     August 2023    
Su Mo Tu We Th Fr Sa
       .  2  3  .  5
 .  7  .  .  .  .  .
 .  .  . 16  .  .  .
 .  .  .  .  . 25  .
 .  .  . 30  .      

2023/08/02 326 45 3.0 1/1 ell
2023/08/03 Swimming ~30 minutes
2023/08/05 Swimming 50min med diff
2023/08/07 393 50 3.48 2/1 elliptical
2023/08/16 345 50 3.29 2/1 elliptical
2023/08/25 1 hour intense swimming
2023/08/30 333 44 3.00 2/2 elliptical

I got so much great feedback from some "FediFriends"* immediately after that post that the next day, I came up with a script to automate the process of creating the "filtered" cal output automatically: fcal.

* post about what that means (for the uninitiated) coming soon

The core of the script is only roughly* 20 lines of shell (glorious things can be done in 20 lines of shell, my good fellow!!), half of which processes command line options (I could never get into using getopt/getopts), the other half of which constructs a sed one-liner to do the actual filtering.

* not counting spaces, comments, individual if/do lines, and super-simple functions like warn() and die()

Feeding the same data printed manually above into fcal yields the following:

~ $ fcal -o Aug 2 3 5 7 16 25 30
     August 2023    
Su Mo Tu We Th Fr Sa
       .  2  3  .  5
 .  7  .  .  .  .  .
 .  .  . 16  .  .  .
 .  .  .  .  . 25  .
 .  .  . 30  .      

Nobody ever said shell was beautiful, but dang if it isn't insanely useful and quick to construct basic things!