Fixed --output=/dev/null on Linux

Closes #252

README.rst

@@ -1280,6 +1280,7 @@ Changelog
     * To make it easier to deal with Windows paths in request items, ``\``
       now only escapes special characters (the ones that are used as key-value
       separators).
+    * Fixed ``--output=/dev/null`` on Linux.
 * `0.8.0`_ (2014-01-25)
     * Added ``field=@file.txt`` and ``field:=@file.json`` for embedding
       the contents of text and JSON files into request data.

httpie/input.py

@@ -5,6 +5,7 @@ import os
 import sys
 import re
 import json
+import errno
 import mimetypes
 import getpass
 from io import BytesIO
@@ -185,7 +186,14 @@ class Parser(ArgumentParser):
             # `stdout`. The file is opened for appending, which isn't what
             # we want in this case.
             self.args.output_file.seek(0)
-            self.args.output_file.truncate()
+            try:
+                self.args.output_file.truncate()
+            except IOError as e:
+                if e.errno == errno.EINVAL:
+                    # E.g. /dev/null on Linux.
+                    pass
+                else:
+                    raise
             self.env.stdout = self.args.output_file
             self.env.stdout_isatty = False
 

tests/test_regressions.py

@@ -1,6 +1,8 @@
 """Miscellaneous regression tests"""
+import pytest
 
 from utils import http, HTTP_OK
+from httpie.compat import is_windows
 
 
 def test_Host_header_overwrite(httpbin):
@@ -14,3 +16,12 @@ def test_Host_header_overwrite(httpbin):
     assert HTTP_OK in r
     assert r.lower().count('host:') == 1
     assert 'host: {0}'.format(host) in r
+
+
+@pytest.mark.skipif(is_windows, reason='Unix-only')
+def test_output_devnull(httpbin):
+    """
+    https://github.com/jakubroztocil/httpie/issues/252
+
+    """
+    http('--output=/dev/null', httpbin + '/get')