While there is loads of software for reading EXIF data from jpeg I could hardly find anything which allowed me to write EXIF data into jpeg. I was searching for something with CLI on Linux. PHP has neat function exif_read_data and exif_thumbnail, but exif_write_data function is missing – time to look into the EXIF specs… …
I found jhead at https://www.sentex.net/~mwandel/jhead/ and it is the next best thing to having nothing at all.
Oh! for the uninitiated – EXIF stands for Exchangeable Image File Format, and is a standard for storing interchange information in image files, especially those using JPEG compression. Most digital cameras now use the EXIF format.