Add --output-file option to mako-render

Added --output-file argument to the Mako command line runner, which allows
a specific output file to be selected.  Pull request courtesy Björn
Dahlgren.

Fixes: #283
Change-Id: Iae7e2d42d5ae4bc6f09663c115bda9e3797ce68c
Pull-request: https://bitbucket.org/zzzeek/mako/pull-requests/27

2 files changed, 22 insertions, 1 deletions

diff --git a/doc/build/unreleased/283.rst b/doc/build/unreleased/283.rst
new file mode 100644
index 0000000..f8cb585
--- /dev/null
+++ b/doc/build/unreleased/283.rst
@@ -0,0 +1,7 @@
+.. change::
+    :tags: feature, commands
+    :tickets: 283
+
+    Added --output-file argument to the Mako command line runner, which allows
+    a specific output file to be selected.  Pull request courtesy Björn
+    Dahlgren.
diff --git a/mako/cmd.py b/mako/cmd.py
index 95de54a..c0f2c75 100755
--- a/mako/cmd.py
+++ b/mako/cmd.py
@@ -4,6 +4,7 @@
 # This module is part of Mako and is released under
 # the MIT License: http://www.opensource.org/licenses/mit-license.php
 from argparse import ArgumentParser
+import io
 from os.path import dirname
 from os.path import isfile
 import sys
@@ -46,11 +47,17 @@ def cmdline(argv=None):
     parser.add_argument(
         "--output-encoding", default=None, help="force output encoding"
     )
+    parser.add_argument(
+        "--output-file",
+        default=None,
+        help="Write to file upon successful render instead of stdout",
+    )
     parser.add_argument("input", nargs="?", default="-")
 
     options = parser.parse_args(argv)
 
     output_encoding = options.output_encoding
+    output_file = options.output_file
 
     if options.input == "-":
         lookup_dirs = options.template_dir or ["."]
@@ -80,9 +87,16 @@ def cmdline(argv=None):
 
     kw = dict([varsplit(var) for var in options.var])
     try:
-        sys.stdout.write(template.render(**kw))
+        rendered = template.render(**kw)
     except:
         _exit()
+    else:
+        if output_file:
+            io.open(output_file, "wt", encoding=output_encoding).write(
+                rendered
+            )
+        else:
+            sys.stdout.write(rendered)
 
 
 if __name__ == "__main__":