> And elisp grep really isn't that slow, accessing the file system is the slow part and that's true for both implementations and both can benefit from aggressive file caching anyway.

Sorry, I never meant elisp grep was slow. I meant _piping_ was slow.

Here's regular bash in tmux:

    $ wc -l fullform_nb.txt 
    1180517 fullform_nb.txt
    
    $ time sort fullform_nn.txt |grep åbryug
    114297  åbryug  åbryug  adj pos m/f ub eint normert     510     1
    114297  åbryug  åbryug  adj pos nøyt ub eint normert    510     4
    114297  åbryug  åbryugare       adj komp normert        510     5
    114297  åbryug  åbryugast       adj sup ub normert      510     6
    114297  åbryug  åbryugaste      adj sup bu normert      510     7
    114297  åbryug  åbryuge adj pos bu eint normert 510     3
    114297  åbryug  åbryuge adj pos fl normert      510     2
    
    real    0m2.888s
    user    0m9.570s
    sys     0m0.132s
eshell:

    $ time sort fullform_nn.txt | grep åbryug
    114297	åbryug	åbryug	adj pos m/f ub eint normert	510	1
    114297	åbryug	åbryug	adj pos nøyt ub eint normert	510	4
    114297	åbryug	åbryugare	adj komp normert	510	5
    114297	åbryug	åbryugast	adj sup ub normert	510	6
    114297	åbryug	åbryugaste	adj sup bu normert	510	7
    114297	åbryug	åbryuge	adj pos bu eint normert	510	3
    114297	åbryug	åbryuge	adj pos fl normert	510	2
    111.725 secs
Note: the output from grep comes after about 20 seconds, then it runs for 90 sec's until time is done. In any case, way slower than bash in tmux (which is as fast as bash outside tmux). (Silly example, but my real oneliners tend to be rather longer and more cryptic …)

And when I try to e.g. "sort -k2,2 -t$'\t' file" it gives zero results, doesn't even tell me whether $'\t' is unsupported, same deal if I try '\t', whereas in bash, if I try a plain '\t', sort at least tells me sort: multi-character tab ‘\\t’. In eshell, I might be mislead to thinking the grep gave zero results. To me, eshell is both slow and dangerous.

I'm happy eshell works for you, but it is just not usable at all for me. OTOH, I'm faster at typing alt-TAB than at C-x b esh RET, so I don't mind having to leave emacs as long as I only ever have to switch between the terminal and emacs.