Writing image to SD card programmatically

Question

I am trying to write a cross-platform (Linux, Mac OS and windows) tool/script which can write .img images to SD cards via an SD card reader connected to the computer. I tried searching a lot for tutorials/references on how this could be done using various languages but I was unable to find anything fruitful.

I want to gain a deeper understanding of the underlying process which happens when images are written to SD cards, and what factors make this process platform dependent. Some kind of guide/blog post of how such a program can be implemented in some language would be wonderful. (dd command can be used on linux and mac os, but I'm exploring the possibility of writing a single uniform program which could do the job on all platforms)

I would like some guidance/references regarding this

Answer 1

From the perspective of an application program, an SD card is just a file. You can write data on the SD card with the same library functions and system calls you would normally use. On Unix-like operating systems, the files corresponding to devices are commonly placed in the folder /dev. For instance, to write the image sd.img on the first SD card on Linux, you could invoke the command dd like this:

dd if=sd.img of=/dev/mmcblk0

This copies the content of sd.img into the SD card. The process is similar but not exactly equal on other platforms.