[ffmpeg] Using and Convent Function 

Convert:

// mov to mp4

ffmpeg -i inputfile.mov -c:v libx264 -c:a aac -vf format=yuv420p -movflags +faststart outputfile.mp4;

//mp4 to gif

ffmpeg -i inputfile.mp4 -pix_fmt rgb24 outputfile.gif;

Do Loop:

//cd to directory

for file in *.mp4; do ffmpeg -i "$file" -pix_fmt rgb24 "${file%.mp4}".gif; done

Do remove space from name file:

//cd to directory

for file in *.gif; do mv "$file" "${file// /_}"; done