From 7b739330bb459401f9c11f0f84912aedc7ee22cd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20H=C3=A4ssler?= <mhssler@gmail.com>
Date: Sat, 9 Nov 2013 21:04:06 +0100
Subject: Add os:unsetenv/1

New BIF os:unsetenv/1 which deletes an environment variable and
returns 'true'.

Does not change any old functionality.

Calls the libc function unsetenv(3) on UNIX and
SetEnvironmentVariableW(key, NULL) on Windows. The unicode support
is the same as for os:getenv and os:putenv.
---
 lib/kernel/doc/src/os.xml | 11 +++++++++++
 lib/kernel/src/os.erl     |  8 +++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

(limited to 'lib/kernel')

diff --git a/lib/kernel/doc/src/os.xml b/lib/kernel/doc/src/os.xml
index 5e182de41d..9122267c40 100644
--- a/lib/kernel/doc/src/os.xml
+++ b/lib/kernel/doc/src/os.xml
@@ -176,6 +176,17 @@ format_utc_timestamp() ->
         </note>
       </desc>
     </func>
+    <func>
+      <name name="unsetenv" arity="1"/>
+      <fsummary>Delete an environment variable</fsummary>
+      <desc>
+	<p>Deletes the environment variable <c><anno>VarName</anno></c>.</p>
+	<p>If Unicode filename encoding is in effect (see the <seealso
+	marker="erts:erl#file_name_encoding">erl manual
+	page</seealso>), the string (<c><anno>VarName</anno></c>) may
+	contain characters with codepoints > 255.</p>
+      </desc>
+    </func>
     <func>
       <name name="version" arity="0"/>
       <fsummary>Return the Operating System version</fsummary>
diff --git a/lib/kernel/src/os.erl b/lib/kernel/src/os.erl
index ded03361ee..9415593485 100644
--- a/lib/kernel/src/os.erl
+++ b/lib/kernel/src/os.erl
@@ -26,7 +26,7 @@
 
 %%% BIFs
 
--export([getenv/0, getenv/1, getpid/0, putenv/2, timestamp/0]).
+-export([getenv/0, getenv/1, getpid/0, putenv/2, timestamp/0, unsetenv/1]).
 
 -spec getenv() -> [string()].
 
@@ -58,6 +58,12 @@ putenv(_, _) ->
 timestamp() ->
     erlang:nif_error(undef).
 
+-spec unsetenv(VarName) -> true when
+      VarName :: string().
+
+unsetenv(_) ->
+    erlang:nif_error(undef).
+
 %%% End of BIFs
 
 -spec type() -> {Osfamily, Osname} when
-- 
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