[shell] Add several functions

dotfiles/lib/functions/add_to_path

@@ -0,0 +1,7 @@
+#!/usr/bin/env sh
+
+function add_to_path {
+	path_lines "$2" | { cat -; echo "$1" } | path_from_lines
+}
+
+add_to_path "$@"

dotfiles/lib/functions/join_by_char

@@ -0,0 +1,22 @@
+#!/usr/bin/env sh
+
+function join_by_char {
+    delimiter="$1"
+    if [ -z "$delimiter" ]; then
+        echo "Please specify a delimiter."
+        return 1
+    fi
+
+    while IFS= read -r line; do
+        # Append the line to the result with the delimiter, but not for the first line
+        if [ -z "$result" ]; then
+            result="$line"
+        else
+            result="$result$delimiter$line"
+        fi
+    done
+
+    echo "$result"
+}
+
+join_by_char "$@"

dotfiles/lib/functions/nixpkgs_source

@@ -0,0 +1,7 @@
+#!/usr/bin/env sh
+
+function nixpkgs_source {
+	nix eval  --expr '<nixpkgs>' --impure
+}
+
+nixpkgs_source

dotfiles/lib/functions/path_from_lines

@@ -0,0 +1,7 @@
+#!/usr/bin/env sh
+
+function path_from_lines {
+	join_by_char ":"
+}
+
+path_from_lines "$@"

dotfiles/lib/functions/path_lines

@@ -1,7 +1,8 @@
 #!/usr/bin/env sh
 
 function path_lines {
-	split_by_char ":" "$PATH"
+	var="${1:-PATH}"
+	split_by_char ":" "${!var}"
 }
 
-path_lines
+path_lines "$@"