From 19fe0d9ae12644b8af9513aa2a8cf7d16f7caa61 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>

Date: Fri, 4 Mar 2016 16:40:30 -0500

Subject: [PATCH] Add posix.redirect2null

This is useful to silence output in forked programs:

https://bugzilla.redhat.com/show_bug.cgi?id=1287918

Tested with the following scriptlet:

%post -p <lua>

pid = posix.fork()

if pid == 0 then

    assert(posix.exec("/bin/sed"))

elseif pid > 0 then

    posix.wait(pid)

end

pid = posix.fork()

if pid == 0 then

    posix.redirect2null(2)

    assert(posix.exec("/bin/awk"))

elseif pid > 0 then

    posix.wait(pid)

end

As expected, the error message from sed is printed, the error message

from awk is not.

---

 luaext/lposix.c | 20 ++++++++++++++++++++

 1 file changed, 20 insertions(+)

diff --git a/luaext/lposix.c b/luaext/lposix.c

index 51ea2b3..c578c5a 100644

--- a/luaext/lposix.c

+++ b/luaext/lposix.c

@@ -819,6 +819,25 @@ static int Pmkstemp(lua_State *L)

 	return 2;

 }

+static int Predirect2null(lua_State *L)

+{

+    int target_fd, fd, r, e;

+

+    if (!have_forked)

+	return luaL_error(L, "silence_file_descriptor not permitted in this context");

+

+    target_fd = luaL_checkinteger(L, 1);

+

+    r = fd = open("/dev/null", O_WRONLY);

+    if (fd >= 0 && fd != target_fd) {

+	r = dup2(fd, target_fd);

+	e = errno;

+	(void) close(fd);

+	errno = e;

+    }

+    return pushresult(L, r, NULL);

+}

+

 static const luaL_Reg R[] =

 {

 	{"access",		Paccess},

@@ -861,6 +880,7 @@ static const luaL_Reg R[] =

 	{"wait",		Pwait},

 	{"setenv",		Psetenv},

 	{"unsetenv",		Punsetenv},

+	{"redirect2null",       Predirect2null},

 	{NULL,			NULL}

 };

-- 

1.9.3