RIOT/examples/filesystem

File system usage example

Description

This basic example shows how to use a file system with RIOT in your embedded application.

In particular, this example shows:

• how to mount/format/unmount a file system, either with spiffs, littlefs, fatfs or constfs
• how to open/read/write/close a file with and without newlib

In RIOT, most file systems use a mtd as flash interface. So to use this example one must define MTD_0. MTD_0 is a pointer to a mtd_dev_t instance.

This example uses littlefs as default file system on the whole mtd. A constfs file system is also demonstrated with two files.

All the RIOT file systems are used through the vfs interface, and on most platforms files can be accessed transparently with open/close/read/write/... functions. With newlib, fopen/fclose/fread/fwrite/... can also be used transparently.

Shell commands

The following commands are available:

• vfs format /nvm0: should be called the first time only, it will format the /nvm0 mountpoint with the configured file system
• vfs mount /nvm0: mount the file system on the configured mount point The constfs file system is mounted automatically on /const when the application starts
• vfs umount /nvm0: unmount /nvm0
• cat <file>: similarly to unix cat unix command, it prints the given <file> on stdout
• tee <file> <str>: similarly to tee unix command, it writes <str> in <file>

Besides of these commands, the default vfs commands can be used, for instance:

• vfs df: shows all mountpoints and used/available file system space
• vfs ls <path>: list files

Example on native with constfs

• Build and run the filesystem example application on the native target:

make -C examples/filesystem all term
[...]
main(): This is RIOT! (Version: 2018.04-devel-/examples/filesystem)
constfs mounted successfully

• List the available files in the constfs predefined partition:

> ls /const
ls /const
/hello-world
/hello-riot
total 2 files

• Print the content of the files:

> cat /const/hello-world
cat /const/hello-world
Hello World!
> cat /const/hello-riot
cat /const/hello-riot
Hello RIOT!