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So if I want to use grep in a small script, do I have to write:

/nix/store/grep-hash -flags files | /nix/store/head-hash

instead of: "grep -flags files | head"?

If it's a one off, you just use something like "nix shell" to add it to your path for running the script.

For non one-off sorts of things, you would substitute in the nix expression "${gnugrep}/bin/grep" the "${gnugrep}" will expand to "/nix/store/grep-hash" and also make a dependency on the gnugrep package, so that the grep install won't get garbage-collected as long as your package is still around.

Here's an example[1] from a package expression for e-mail client I use, which will shell out to base64 and file. Upstream relies on these two programs being in $PATH, but this replaces the string used for shelling out with the absolute path in the nix store.

For shell scripts, I'll just do something like this near the top:

   GREP="${GNU_GREP:-$(command -v grep)}"

Then I use "$GREP" in the script itself, and develop with grep in my path, but it's trivial to prepend all of my dependencies when I bundle it up for nix.

1: https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/no...

xaduha 8 hours ago [ - ]

    [user@nixos:~]$ which grep
    /run/current-system/sw/bin/grep

    [user@nixos:~]$ ls -l /run/current-system/sw/bin/grep
    lrwxrwxrwx 1 root root 65 Jan  1  1970 /run/current-system/sw/bin/grep -> /nix/store/737jwbhw8ji13x9s88z3wpp8pxaqla92-gnugrep-3.12/bin/grep

Basically, it is still in your environment, so I don't see how he can claim that this problem doesn't exist in Nix, unless you use flakes like a proper Nix afficionado.

aidenn0 5 hours ago [ - ]

Yes, the original comment that this problem doesn't exist in Nix is wrong for a typical user environment.

It does contain the issue a bit though:

I'm running isync in a systemd service, yet the program "mbsync" is not in my path. I have several services installed, yet their programs aren't in my path. My e-mail client shells out to "file" for mime-type verification, yet "file" is not in my path.

Run "compgen -c |wc -l" to get a list of commands; its over 7000 on my Ubuntu system and right around 2000 on my NixOS system.

As an aside, the packages that put the most executables in my path are probably going to be in the path for most NixOS installs (231 just for coreutils+util-linux):

     27 /nix/store/csxa6mi2mpjl9vqxbv2j0bha6sz6nbjw-cups-2.4.14
     31 /nix/store/334afxah19b3hr6ll93pfxlcyhhh2vws-pipewire-1.4.9
     31 /nix/store/h2jsb5i4yfblr2f3ac2c7zpmlmj7zjym-perl-5.40.0
     33 /nix/store/914x32c982bs3i1998yxvkg9svm3ycr5-shadow-4.18.0
     33 /nix/store/a6s3hzj3b2z6rsyfkjyxwn265iyfl2gn-mtools-4.0.49
     33 /nix/store/jky7jszaci5n7g426wf6nsg5dmik9nfw-kbd-2.9.0
     37 /nix/store/2v1l6mqz0d7mfpp4ksw2048v3g0a1a19-hplip-3.25.2
     45 /nix/store/90wlc37ljr6rpy2lan46bp0gq19vbgl5-iptables-1.8.11
     48 /nix/store/1byhxs7b28grh8s15jc2dvs2zg36swjb-lvm2-2.03.35-bin
     61 /nix/store/9xwxjkrwxjsvc5gs1l0syr4wbfvvvvcn-bluez-5.84
     64 /nix/store/zf8qy81dsw1vqwgh9p9n2h40s1k0g2l1-systemd-258.2
     72 /nix/store/1igrj9w84w7s3r80l3nkxcqwd84sw9mz-qemu-10.1.2
    106 /nix/store/v4q3154vdc83fxsal9syg9yppshdljyk-coreutils-full-9.8
    125 /nix/store/3c6r8gh8zrqw8xmncmlj9vivz9rz6r30-util-linux-2.41.2-bin

xaduha 5 hours ago [ - ]

True enough, but in my experience it's not really much of a problem because if I'm not doing Nix, then I'm doing containers which are widely available.

What can be a problem is muscle memory, when you expect it to autocomplete one way and it doesn't because something you want now shares first two or three letters with something else in your path. That's where FIGNORE comes in.