UNIX philosophy.

Why is the opposite of cat tee, and it's not even a proper opposite but also does a different thing (outputs to stdout) (which is ostensibly its real purpose)?

Also, why do I even need the opposite of cat (and cat itself while we are at it) when those needs should have been served by input and output redirection, but turns out that the latter is completely made up and broken shell bullshit: you can't cat <file1 <file2, and you can't EDITOR='echo zzz >>$1' visudo for example.

Orthogonal design, my ass. Do one thing and do it well, my ass.

>>2,3
Ffs. cat reads data from one or more files and outputs it on stdout. I needed a program that reads data from stdin and saves it into a file. Because I wanted to give it as an EDITOR to visudo, as per provided example.

This simple desire, this humble need, this quiet longing unexpectedly led me to various horrible discoveries. From the terrible realization that the only available utility that can serve the role that is the reverse of cat's happens to be tee (and it serves it badly), to the chilling realization that input/output redirection is a woefully incomplete hack, that's why we need cat and tee in the first place.

Since my first post I also checked the source code of visudo and the hair on my head stood on ends and started writhing, as if I've spent years washing them several times a day with the best female shampoos, giving them extraordinary health, thickness, and vitality. It parses the command manually! Splitting it on spaces and tabs! So no, you can't specify an editor with spaces in path, nor give it quoted arguments with spaces!