Not working

peters-macbook-pro:~ peter$ cd Desktop
peters-macbook-pro:Desktop peter$ ffmpeg -f concat -safe 0 -i <(printf "file '/Users/peter/Desktop/WordHeadingsWo.mp4'\nfile '/Users/peter/Desktop/WordClipsWo.mp4'\n") -c copy "WordsWoFailed.mp4"
ffmpeg version 2.6.2 Copyright (c) 2000-2015 the FFmpeg developers
  built with Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.6.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-vda
  libavutil      54. 20.100 / 54. 20.100
  libavcodec     56. 26.100 / 56. 26.100
  libavformat    56. 25.101 / 56. 25.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 11.102 /  5. 11.102
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, concat, from '/dev/fd/63':
  Duration: N/A, start: 0.000000, bitrate: 140 kb/s
    Stream #0:0: Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 1280x934 [SAR 1:1 DAR 640:467], 68 kb/s, 24 fps, 24 tbr, 12288 tbn, 48 tbc
    Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 71 kb/s
Output #0, mp4, to 'WordsWoFailed.mp4':
  Metadata:
    encoder         : Lavf56.25.101
    Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 1280x934 [SAR 1:1 DAR 640:467], q=2-31, 68 kb/s, 24 fps, 24 tbr, 12288 tbn, 12288 tbc
    Stream #0:1: Audio: aac ([64][0][0][0] / 0x0040), 48000 Hz, mono, 71 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
[mp4 @ 0x7f8ffa802a00] Non-monotonous DTS in output stream 0:0; previous: 48902, current: 48534; changing to 48903. This may result in incorrect timestamps in the output file.
frame= 2138 fps=0.0 q=-1.0 size=   17415kB time=00:01:29.96 bitrate=1585.8kbits/frame= 3617 fps=3440 q=-1.0 size=   27675kB time=00:02:32.31 bitrate=1488.4kbitsframe= 4969 fps=3106 q=-1.0 size=   37930kB time=00:03:29.39 bitrate=1483.9kbitsframe= 6453 fps=3033 q=-1.0 size=   48129kB time=00:04:31.82 bitrate=1450.5kbitsframe= 7812 fps=2946 q=-1.0 size=   57346kB time=00:05:29.03 bitrate=1427.7kbitsframe= 9137 fps=2868 q=-1.0 size=   67618kB time=00:06:24.62 bitrate=1440.2kbitsframe=10843 fps=2942 q=-1.0 size=   78375kB time=00:07frame=13882 fps=2959 q=-1.0 size=  100244kB time=00:09:43.61 bitraframe=22747 fps=2866 q=-1.0 Lsize=  162244kB time=00:15:56.85 bitrate=1389.0kbits/s
video:146738kB audio:14994kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.316447%
peters-macbook-pro:Desktop peter$