files are generated in TMPDIR

fixes #4

techrec/forge.py

@@ -1,4 +1,5 @@
 import logging
+import tempfile
 import os
 from datetime import datetime, timedelta
 from subprocess import Popen
@@ -121,8 +122,10 @@ def create_mp3(start, end, outfile, options={}, **kwargs):
         metadata_list.append("-metadata")
         metadata_list.append("%s=%s" % (tag, value))
 
+    prefix, suffix = os.path.basename(outfile).split('.', 1)
+    tmp_file = tempfile.NamedTemporaryFile(suffix='.%s' % suffix, prefix='forge-%s' % prefix, delete=False)
     p = Popen(
-        mp3_join(intervals) + metadata_list + get_config()["FFMPEG_OPTIONS"] + [outfile]
+        mp3_join(intervals) + metadata_list + ['-y'] + get_config()["FFMPEG_OPTIONS"] + [tmp_file.name]
     )
     if get_config()["FORGE_TIMEOUT"] == 0:
         p.wait()
@@ -137,12 +140,13 @@ def create_mp3(start, end, outfile, options={}, **kwargs):
     if p.returncode is None:
         os.kill(p.pid, 15)
         try:
-            os.remove(outfile)
+            os.remove(tmp_file.name)
         except:
             pass
         raise Exception("timeout")  # TODO: make a specific TimeoutError
     if p.returncode != 0:
         raise OSError("return code was %d" % p.returncode)
+    os.rename(tmp_file.name, outfile)
     return True