exiftool command in README not working

[reteptilian]

In

exiftool -overwrite_original -r -if 'not defined DateTimeOriginal' -P "-AllDates<FileModifyDate" "your/output/folder/ALL_PHOTOS/"

The DateTimeOriginal in the "-if" snippet needs to be prefixed with $.

For example:

# This file doesn't have DateTimeOriginal. It has a FileModifyDate
$ exiftool -DateTimeOriginal -FileModifyDate ./ALL_PHOTOS/IMG_6872.MOV
File Modification Date/Time     : 2016:11:24 14:29:42-08:00

# Try the command in the README (without -r). Note the "failed condition" error message.
$ exiftool -overwrite_original  -if 'not defined DateTimeOriginal' -P "-AllDates<FileModifyDate" ./ALL_PHOTOS/IMG_6872.MOV
    1 files failed condition

# Still no DateTimeOriginal
esbensen@newxps:/data2/photos/organized$ exiftool -DateTimeOriginal -FileModifyDate ./ALL_PHOTOS/IMG_6872.MOV
File Modification Date/Time     : 2016:11:24 14:29:42-08:00

# Try again with $DateTimeOriginal
$ exiftool -overwrite_original  -if 'not defined $DateTimeOriginal' -P "-AllDates<FileModifyDate" ./ALL_PHOTOS/IMG_6872.MOV
    1 image files updated

# It worked
$ exiftool -DateTimeOriginal -FileModifyDate ./ALL_PHOTOS/IMG_6872.MOV
Date/Time Original              : 2016:11:24 14:29:42-08:00
File Modification Date/Time     : 2016:11:24 14:29:42-08:00