/dev/fs
< /dev
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The filesystem can be directly accessed through "/dev/fs".
There are several IOS functions for FS like Delete/Create/List/Rename/.. .
Files can be directly opened with IOS_Open("/tmp/data.bin",1);
The root folder contains these subfolders, some of which have their own pages:
/wfs (4.3 only)
Ioctl listing
| Request number | Name | input | output | notes | 
| 0x1 | Format | - | - | Can only be called by UID 0. Deletes the entire FS, not like the System Menu button. Will probably brick the console. Do not use! | 
| 0x2 | GetStats | - | 0x1C bytes: 7 u32's: cluster size, free clusters, used clusters, bad clusters, reserved clusters, free inodes, used inodes. | |
| 0x3 | CreateDir | 0x4A bytes: 4 for owner ID, 2 for group ID, 0x40 filename, 1 for each owner/group/other permissions, 1 for attributes. | 0 | |
| 0x4 | ReadDir | Directory name (0x40), Max file count (0x4) | File names (0x13*maxFileCount), File count (0x4) | |
| 0x5 | SetAttr | See CreateDir input. | - | |
| 0x6 | GetAttr | 64 bytes for filename | See CreateDir input. | |
| 0x7 | Delete | 64 bytes for filename | - | |
| 0x8 | Rename | 64 bytes for source, 64 bytes for destination | - | |
| 0x9 | CreateFile | See CreateDir input. Owner ID and group ID will not be used. | 0 | |
| 0xa | SetFileVerCtrl | ? | ? | |
| 0xb | GetFileStats | - | 8 bytes: 4 bytes for file size, 4 bytes for seek position | |
| 0xc <ioctlv> | GetUsage | 64 bytes for filename | 4 bytes for used clusters, 4 bytes for used inodes | |
| 0xd | Shutdown | - | - | Disables the NAND and refuses any further IPC requests with error -119. | 
| 0xe <ioctlv> | ????? | List of paths for the files to create. Last vector is an array of u32's with the file sizes. | - | Creates and allocates a list of files in one go. Somehow not used by ES, despite probably being the one to benefit the most from such a function. | 
/dev/fs error codes
| Error code | POSIX equivalent | notes | 
| -101 | EINVAL | Invalid argument | 
| -102 | EACCES | Permission denied | 
| -103 | EIO | Failed to write to any of the 16 superblocks | 
| -104 | ? | Filesystem not found ES will call Format if GetStats returns this error code. | 
| -105 | EEXIST | File exists | 
| -106 | ENOENT | File not found | 
| -107 | ENOSPC | Filesystem is full (no free inodes) | 
| -108 | ENOSPC | Filesystem is full (no free clusters) | 
| -109 | ENFILE | Too many fds open (16; includes /dev/fs) | 
| -110 | ENAMETOOLONG | Max directory depth exceeded (8) | 
| -111 | ETXTBSY | Trying to delete a currently open file | 
| -112 | ? | This block is bad (-13) | 
| -113 | ? | ECC error (corrected) (-11) | 
| -114 | EIO | ECC error (uncorrectable) (-12) | 
| -115 | ENOTEMPTY * | File is not empty | 
| -116 | ? | Cluster verification failed | 
| -117 | - | unknown error | 
| -118 | EBUSY | Resource busy | 
| -119 | ESHUTDOWN | The filesystem has been shut down |