Remove all lines starting with # in a file

Soak up the input before writing the output file.
More information: <https://manned.org/sponge>.
Trick copyright: tl;dr; <https://github.com/tldr-pages/tldr>

grep -v '^{{#}}' {{path/to/file}} | sponge {{path/to/file}}

click the source code to copy install sponge on any operating system with command-not-found.com