[RFC PATCH 1/2] Add $_env convenience function

[Keith Seitz <keiths@redhat.com>]

This patch adds a new Python convenience function which simply
returns the value of the given environment variable or throws
a KeyError.

(gdb) p $_env("HOME")
$1 = "/home/keiths"

[This patch is here for the purposes of demonstarting an alternative
design/implementation to a previously proposed patch. See
https://sourceware.org/pipermail/gdb-patches/2022-October/192396.html .]
---
 gdb/data-directory/Makefile.in     |  1 +
 gdb/python/lib/gdb/function/env.py | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 gdb/python/lib/gdb/function/env.py

diff --git a/gdb/data-directory/Makefile.in b/gdb/data-directory/Makefile.in
index f1139291eed..3b0a05d61dc 100644
--- a/gdb/data-directory/Makefile.in
+++ b/gdb/data-directory/Makefile.in
@@ -107,6 +107,7 @@ PYTHON_FILE_LIST = \
 	gdb/function/as_string.py \
 	gdb/function/caller_is.py \
 	gdb/function/strfns.py \
+	gdb/function/env.py \
 	gdb/printer/__init__.py \
 	gdb/printer/bound_registers.py
 
diff --git a/gdb/python/lib/gdb/function/env.py b/gdb/python/lib/gdb/function/env.py
new file mode 100644
index 00000000000..54a441cea54
--- /dev/null
+++ b/gdb/python/lib/gdb/function/env.py
@@ -0,0 +1,21 @@
+"""$_env"""
+
+import gdb
+import os
+
+class _Env(gdb.Function):
+    """$_env - return the value of an environment variable.
+
+    Usage: $_env("NAME")
+
+    Returns:
+      Value of the environment variable named NAME or throws KeyError if NAME is
+      undefined in the environment."""
+
+    def __init__(self):
+        super(_Env, self).__init__("_env")
+
+    def invoke(self, name):
+        return os.environ[name.string()]
+
+_Env()
-- 
2.38.1