lib: import shell from krebs/4lib

2 files changed, 28 insertions, 0 deletions

diff --git a/lib/default.nix b/lib/default.nix
new file mode 100644
index 000000000..6c607f13b
--- /dev/null
+++ b/lib/default.nix
@@ -0,0 +1,7 @@
+let
+  lib = import <nixpkgs/lib> // builtins // {
+    shell = import ./shell.nix { inherit lib; };
+  };
+in
+
+lib
diff --git a/lib/shell.nix b/lib/shell.nix
new file mode 100644
index 000000000..a8ff5dbe0
--- /dev/null
+++ b/lib/shell.nix
@@ -0,0 +1,21 @@
+{ lib, ... }:
+
+with lib;
+
+rec {
+  escape =
+    let
+      isSafeChar = c: match "[-+./0-9:=A-Z_a-z]" c != null;
+    in
+    stringAsChars (c:
+      if isSafeChar c then c
+      else if c == "\n" then "'\n'"
+      else "\\${c}");
+
+  #
+  # shell script generators
+  #
+
+  # example: "${cat (toJSON { foo = "bar"; })} | jq -r .foo"
+  cat = s: "printf '%s' ${escape s}";
+}