-a

automatic (using exif orientation tag)

-9

rotate by 90 degrees

-1

rotate by 180 degrees

-2

rotate by 270 degrees

-f

flip vertical

-F

flip horizontal

-t

transpose

-T

transverse

-nt

Don't rotate exif thumbnail.

-ni

Don't rotate jpeg image. You might need this or or the -nt option to fixup things in case you rotated the image with some utility which ignores the exif thumbnail. Just generating a new thumbnail with -g is another way to fix it.

-no

Don't update the orientation tag. By default exiftran sets the orientation to "1" (no transformation needed) to avoid other exif-aware applications try to rotate the already-rotated image again.

-h

print a short help text

-d

Dump exif data for the file(s).

-c <text>

Set jpeg comment tag to <text>.

-g

(re)generate EXIF thumbnail.

-o <file>

Specify output file. Only one input file is allowed in this mode.

-i

Enable inplace editing of the images. Exiftran allows multiple input files then. You must specify either this option or a output file with -o for all operations which modify the image (i.e. everything but -d right now).

-b

Create a backup file when doing inplace editing.

-p

Preserve timestamps (atime + mtime) when doing inplace editing.

   exiftran -ai *.jpeg