pathname: improvements, cleanups, and new methods

- atomic_write: close file before renaming to prevent error:
  'Device or resource busy'
- ensure_writable: preserve executable bit
- new elf? and dynamic? methods

1 files changed, 19 insertions, 0 deletions

diff --git a/Library/Homebrew/extend/os/linux/extend/pathname.rb b/Library/Homebrew/extend/os/linux/extend/pathname.rb
new file mode 100644
index 000000000..eb6ea409b
--- /dev/null
+++ b/Library/Homebrew/extend/os/linux/extend/pathname.rb
@@ -0,0 +1,19 @@
+class Pathname
+  # @private
+  def elf?
+    # See: https://en.wikipedia.org/wiki/Executable_and_Linkable_Format#File_header
+    read(4) == "\x7fELF"
+  end
+
+  # @private
+  def dynamic_elf?
+    if which "readelf"
+      popen_read("readelf", "-l", to_path).include?(" DYNAMIC ")
+    elsif which "file"
+      !popen_read("file", "-L", "-b", to_path)[/dynamic|shared/].nil?
+    else
+      raise StandardError, "Neither `readelf` nor `file` is available "\
+        "to determine whether '#{self}' is dynamically or statically linked."
+    end
+  end
+end