lib: add fileutils file with stream error checking facility

The close_stream() is copied from GNU lib. Inspiration to do this
is talk by Jim Meyering - Goodbye World! The perils of relying on
output streams in C.

Reference: http://www.irill.org/events/ghm-gnu-hackers-meeting/videos/jim-meyering-goodbye-world-the-perils-of-relying-on-output-streams-in-c
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

testsuite/lib.test/fileutils.exp

@@ -0,0 +1,19 @@
+#
+# Testsuite for lib/fileutils program
+#
+
+set noarg "${topdir}lib/test_fileutils"
+
+set test "without argument"
+spawn $noarg
+expect_pass "$test" "Hello, World!"
+
+set badfd "${topdir}testsuite/lib.test/fileutils_badfd.sh"
+set test "test bad file descriptor"
+spawn $badfd
+expect_pass "$test" "test_fileutils: write error: Bad file descriptor"
+
+set full "${topdir}testsuite/lib.test/fileutils_full.sh"
+set test "test no space left on device"
+spawn $full
+expect_pass "$test" "test_fileutils: write error: No space left on device"

testsuite/lib.test/fileutils_badfd.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+BASEDIR=$(dirname ${0})
+${BASEDIR}/../../lib/test_fileutils >&-

testsuite/lib.test/fileutils_full.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+BASEDIR=$(dirname ${0})
+${BASEDIR}/../../lib/test_fileutils > /dev/full