Should the sdcard support case-sensitive files?

Question

I've been testing one of my apps to see how it handles filenames in UPPER-CASE. I thought the Android libraries and system was case sensitive for filenames, however I eventually discovered that files on the SD card are matched without case-sensitivity.

Here's an example taken from a Samsung Ace phone (my Nexus 4 behaves similarly)

adb shell

$ pwd
/mnt/sdcard/testDaisyReader/casesensitivebook

$ echo "" > NCC.HTML
$ ls -l
-rwxrwxr-x system   sdcard_rw        1 2013-11-19 18:57 NCC.HTML
$ ls -l NCC.HTML
-rwxrwxr-x system   sdcard_rw        1 2013-11-19 18:57 NCC.HTML
$ ls -l ncc.html
-rwxrwxr-x system   sdcard_rw        1 2013-11-19 18:57 ncc.html
$ ls -l
-rwxrwxr-x system   sdcard_rw        1 2013-11-19 18:57 NCC.HTML
$ 

I would have expected the commands ls -l ncc.html wouldn't find the file I created, however it seems to do so. My Android app also matches files without case-sensitivity.

Do any of you have any counter-examples? I'd like to know whether it's safe to assume filenames are matched on the SD-Card in Android, like Windows, without case-sensitivity.

Notes: 1. the filesystem on the SD-Cards are FAT32 2. I've found 2 related posts that imply files on the sdcard are case-sensitive:

How can I open an HTML file I have copied from PC to SD Card of Phone?

How can I determine the SD card's path?

Answer 1

Android itself is based on Linux, which is designed for case-sensitive filesystems. Internal storage is usually on an ext or ext4 filesystem, which is case-sensitive. SD cards are usually formatted with FAT 32, which is a case-insensitive filesystem. Although Android can support using other filesystems on the SD card, Windows PCs can't, so it's unusual to format your SD card with a different filesystem, and if you do this, you can't use the SD card in a Windows PC (via a card-reader), nor can you have the phone act as a USB mass storage device when connected to a PC.