Shell 腳本
函數 writeShellScript 可用於向 Nix 表達式中添加 Shell 腳本。
someBuildHelper = { name, sha256 }:
stdenv.mkDerivation {
inherit name;
outputHashMode = "recursive";
outputHashAlgo = "sha256";
outputHash = sha256;
builder = writeShellScript "builder.sh" ''
echo "hi, my name is ''${0}" # escape bash variable
echo "hi, my hash is ${sha256}" # use nix variable
echo "hello world" >output.txt
'';
};
外部 builder.sh 腳本
較長的 Bash 腳本通常會保存為外部腳本文件，並在 Nix 中調用：
❄︎ default.nix
{
outputTxtDrv = stdenv.mkDerivation rec {
name = "output.txt";
# disable unpackPhase etc
phases = "buildPhase";
builder = ./builder.sh;
nativeBuildInputs = [ coreutils jq ];
PATH = lib.makeBinPath nativeBuildInputs;
# only strings can be passed to builder
someString = "hello";
someNumber = builtins.toString 42;
someJson = builtins.toJSON { dst = "world"; };
};
}
≡︎ builder.sh
jq -r '.dst') $someNumber" >$out
另見：
runCommand + builder.sh
除了使用 stdenv.mkDerivation 之外，還可以通過 runCommand 來調用外部的 Bash 腳本：
❄︎ default.nix
{
outputTxtDrv = runCommand "output.txt" {
nativeBuildInputs = [ coreutils jq ];
# only strings can be passed to builder
someString = "hello";
someNumber = builtins.toString 42;
someJson = builtins.toJSON { dst = "world"; };
} (builtins.readFile ./builder.sh);
}
打包
示例：
# nix-build -E 'with import <nixpkgs> { }; callPackage ./default.nix { }'
{ stdenv
, lib
, fetchFromGitHub
, bash
, subversion
, makeWrapper
}:
stdenv.mkDerivation {
pname = "github-downloader";
version = "08049f6";
src = fetchFromGitHub {
# https://github.com/Decad/github-downloader
owner = "Decad";
repo = "github-downloader";
rev = "08049f6183e559a9a97b1d144c070a36118cca97";
sha256 = "073jkky5svrb7hmbx3ycgzpb37hdap7nd9i0id5b5yxlcnf7930r";
};
buildInputs = [ bash subversion ];
nativeBuildInputs = [ makeWrapper ];
installPhase = ''
mkdir -p $out/bin
cp github-downloader.sh $out/bin/github-downloader.sh
wrapProgram $out/bin/github-downloader.sh \
--prefix PATH : ${lib.makeBinPath [ bash subversion ]}
'';
}
wrapProgram 會將原始腳本移動到 .github-downloader.sh-wrapped。
命令未找到
例如，腳本會拋出錯誤 svn: command not found，這是因為缺少依賴包 subversion。
當某個命令缺失時，可以使用 nix-locate 來查找對應的軟體包名稱。例如，stat 命令：
$ nix-locate bin/stat | grep 'bin/stat$'
coreutils.out 0 s /nix/store/vr96j3cxj75xsczl8pzrgsv1k57hcxyp-coreutils-8.31/bin/stat
調試嵌入腳本
當 Bash 腳本執行失敗時，它只會輸出錯誤信息，而不會顯示出錯的代碼位置。
要跟蹤命令和行號，可以使用
❄︎ test-trace.nix
{ runCommand, coreutils }:
runCommand "output.txt" { nativeBuildInputs = [ coreutils ]; } ''
# line 5 in nix file = line 1 in bash script -> offset 4
PS4='+ Line $(expr $LINENO + 4): '
set -o xtrace # print commands
echo hello >$out # line 9 in nix file
set +o xtrace # hide commands
''
$ nix-build -E 'with import <nixpkgs> { }; callPackage ./test-trace.nix { }'
this derivation will be built:
/nix/store/2v5biwny8plpyk2bv6cfr41ppp0a1i4k-output.txt.drv
building '/nix/store/2v5biwny8plpyk2bv6cfr41ppp0a1i4k-output.txt.drv'...
++ Line 9: echo hello
++ Line 11: set +o xtrace
/nix/store/ppidmnpd5m762x9kqj8jd3g7df7dknrz-output.txt
POSIX shell
某些環境（例如基於 BusyBox 的 OpenWRT）僅提供「受限」 Shell（使用 sh 而非 bash）
在 NixOS 上，POSIX shells 由軟體包 dash 和 posh 提供。