[FFmpeg-user] why is ffmpeg trying to overwrite an input file?

[Dave Stevens]

I have about 100  png files that are named with their creation date
like this: '2019-10-18-204759_1366x768_scrot.png' . The collating
sequence is the same as their chronological sequence. I found what
seemed to be a reasonable suggestion to use:

ffmpeg -framerate 24 -i *.png output.mp4

to make a single mp4 of about four seconds duration. But I'm getting
an unexpected message about overwriting an input file, like this:

$ ffmpeg -framerate 24 -i *.png output.mp4
ffmpeg version 2.8.15-0ubuntu0.16.04.1 Copyright (c) 2000-2018 the
FFmpeg developers built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10)
20160609 configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1
--build-suffix=-ffmpeg --toolchain=hardened
--libdir=/usr/lib/x86_64-linux-gnu
--incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl
--enable-shared --disable-stripping --disable-decoder=libopenjpeg
--disable-decoder=libschroedinger --enable-avresample --enable-avisynth
--enable-gnutls --enable-ladspa --enable-libass --enable-libbluray
--enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite
--enable-libfontconfig --enable-libfreetype --enable-libfribidi
--enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame
--enable-libopenjpeg --enable-libopus --enable-libpulse
--enable-librtmp --enable-libschroedinger --enable-libshine
--enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh
--enable-libtheora --enable-libtwolame --enable-libvorbis
--enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265
--enable-libxvid --enable-libzvbi --enable-openal --enable-opengl
--enable-x11grab --enable-libdc1394 --enable-libiec61883
--enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
WARNING: library configuration mismatch avcodec     configuration:
--prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg
--toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu
--incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl
--enable-shared --disable-stripping --disable-decoder=libopenjpeg
--disable-decoder=libschroedinger --enable-avresample --enable-avisynth
--enable-gnutls --enable-ladspa --enable-libass --enable-libbluray
--enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite
--enable-libfontconfig --enable-libfreetype --enable-libfribidi
--enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame
--enable-libopenjpeg --enable-libopus --enable-libpulse
--enable-librtmp --enable-libschroedinger --enable-libshine
--enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh
--enable-libtheora --enable-libtwolame --enable-libvorbis
--enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265
--enable-libxvid --enable-libzvbi --enable-openal --enable-opengl
--enable-x11grab --enable-libdc1394 --enable-libiec61883
--enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
--enable-version3 --disable-doc --disable-programs --disable-avdevice
--disable-avfilter --disable-avformat --disable-avresample
--disable-postproc --disable-swscale --enable-libopencore_amrnb
--enable-libopencore_amrwb --enable-libvo_aacenc
--enable-libvo_amrwbenc libavutil      54. 31.100 / 54. 31.100
libavcodec     56. 60.100 / 56. 60.100 libavformat    56. 40.101 / 56.
40.101 libavdevice    56.  4.100 / 56.  4.100 libavfilter     5.
40.101 /  5. 40.101 libavresample   2.  1.  0 /  2.  1.  0
libswscale      3.  1.101 /  3.  1.101 libswresample   1.  2.101 /  1.
2.101 libpostproc    53.  3.100 / 53.  3.100 Input #0, png_pipe, from
'2019-10-18-204639_1366x768_scrot.png': Duration: N/A, bitrate: N/A
Stream #0:0: Video: png, rgb24(pc), 1366x768, 24 tbr, 24 tbn, 24 tbc
File '2019-10-18-204759_1366x768_scrot.png' already exists. Overwrite ?
[y/N] n Not overwriting - exiting

can anyone suggest what I'm doing wrong?

Dave