lib: utils: Add is_a_tty()

This is a portable version of POSIX's isatty(). Windows has its own
version, called _isatty(). UHD thus gains its own, portable version.
The underscores aren't beautiful, but they're necessary so we can
distinguish the POSIX version from the UHD version.

2 files changed, 33 insertions, 0 deletions

diff --git a/host/tests/CMakeLists.txt b/host/tests/CMakeLists.txt
index a7d2120aa..769c09796 100644
--- a/host/tests/CMakeLists.txt
+++ b/host/tests/CMakeLists.txt
@@ -34,6 +34,7 @@ set(test_sources
     fp_compare_delta_test.cpp
     fp_compare_epsilon_test.cpp
     gain_group_test.cpp
+    isatty_test.cpp
     log_test.cpp
     math_test.cpp
     narrow_cast_test.cpp
diff --git a/host/tests/isatty_test.cpp b/host/tests/isatty_test.cpp
new file mode 100644
index 000000000..dfeebfd25
--- /dev/null
+++ b/host/tests/isatty_test.cpp
@@ -0,0 +1,32 @@
+//
+// Copyright 2019 Ettus Research, a National Instruments Brand
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+
+#include <uhdlib/utils/isatty.hpp>
+#include <boost/test/unit_test.hpp>
+#include <iostream>
+#include <stdio.h>
+
+BOOST_AUTO_TEST_CASE(test_isatty)
+{
+    // We can't really pass or fail based on the result, because it depends on
+    // how the tests are executed. We'll just run it and see it doesn't crash.
+    if (uhd::is_a_tty(2)) {
+        std::cout << "stderr is a TTY" << std::endl;
+    } else {
+        std::cout << "stderr is not a TTY" << std::endl;
+    }
+
+    FILE* tmp_file = std::tmpfile();
+#ifdef UHD_PLATFORM_WIN32
+    BOOST_REQUIRE(!uhd::is_a_tty(_fileno(tmp_file)));
+#elif _POSIX_C_SOURCE >= _200112L
+    BOOST_REQUIRE(!uhd::is_a_tty(fileno(tmp_file)));
+#else
+    // I got 99 problems but dealing with portability ain't one
+    BOOST_REQUIRE(!uhd::is_a_tty(99));
+#endif
+}
+