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.

1 files changed, 10 insertions, 0 deletions

diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index 401b37b9d2..61f9f6a59a 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -2489,6 +2489,16 @@ erts_sys_getenv(char *key, char *value, size_t *size)
     return res;
 }
 
+int
+erts_sys_unsetenv(char *key)
+{
+    int res;
+    erts_smp_rwmtx_rwlock(&environ_rwmtx);
+    res = unsetenv(key);
+    erts_smp_rwmtx_rwunlock(&environ_rwmtx);
+    return res;
+}
+
 void
 sys_init_io(void)
 {