I use Keil's file system on a NXP ARM with SD Card. I want to create filenames in lowercase, but when I initialise a string, e.g. strcpy(file_str, "myfile.dat") and do a fopen() with that name it creates a file using uppercase letters.
By chance I found that if I do a strcat after I initialised the string, e.g. strcat(file_str, "_anything") and then do a fopen() the file is created with lowercase letters.
Can someone explain this and how can I create files using lowercase letters?
Thanks for your reply: I'm not in control of where and on what machine the SD card might be read. So I would like to store it in a case that is predicable and prefer lower case. As far as I know the FAT spec says it must "preserve" case but is not case sensitive. That means if I want to create a file in lowercase it should not mess with the case.
I think I've discovered a bug and would like to know from Keil what fix they would suggest.
I'm not in control of where and on what machine the SD card might be read.
That has nothing to do with it, really.
As far as I know the FAT spec says it must "preserve" case but is not case sensitive.
You know that incorrectly, or at least incompletely. FAT exists in several versions, all of case-insensitive. But it's wrong to assume they all preserve case.
* The original old FAT-12 or FAT-16 systems didn't preserve case. All file names are actually UPPERCASE on disk, even if the file was created with a lowercase name.
* With Win95 Microsoft plugged an extension onto these file systems: VFAT. This abuses directory entries marked as "deleted file" to store long names and allows them to be mixed-case. It still has to keep the genuine short 11.3 FAT filename around, though, because that's the only one all implementations of FAT12/FAT16 are actually required to keep alive. This nonsense is what gave the world stupid things like c:\Progra~1\Micros~1\.
* I never bothered to find out if FAT32 (introduced with Win95 OSR2, a.k.a. Win95b, needed if you want volumes bigger than 2GiB) supports mixed-case names directly, or still via that dreaded VFAT nonsense.
To cut this long story short: if you really want the name of that file preserved as you created it you have no choice: it has to be short (11.3 format) and UPPERCASE.
Thanks for the info.
Although I accept that all file names will be uppercase I still find it curous that the moment you do a strcat on a filename before creating it, it creates the file using lowercase.
I haven't access to the file system - and to my knowledge, the manual is only available with the license.
Anyway - when using VFAG and long file names, then the FAT file system will preserve case (but still be case-insensitive for name matches). So if the Keil implementation support long file names, then your concatenation will no longer represent a 8.3 name, and the exact name will be used.