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"?
/nix/store/grep-hash -flags files | /nix/store/head-hash
instead of: "grep -flags files | head"?
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:-$(command -v grep)}"
1: https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/no...
[user@nixos:~]$ 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
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-binWhat 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.