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{{ENG-CANSAT-PICO-NAV}}
{{ENG-CANSAT-PICO-NAV}}
== MicroPython File System ==
== MicroPython File System ==
MicroPython board does fits an internal file system. This means that Python language on a MicroPython board can also manage files!
MicroPython board does fits an internal file system. This means that Python language on a MicroPython board can also manage files and directories! Exactly like python does on a computer :-).
[[Fichier:MicroPython-FileSystem.png|256px]]
[[Fichier:MicroPython-FileSystem.png|256px]]
=== Reading data from text file ===
=== Reading data from text file ===
The following script read the content of the "file2.txt" text file and displays it on the REPL output.
== File-system, Writing and data lost ==
<syntaxhighlight lang="python">
with open( 'file2.txt', 'r' ) as _file:
s = _file.readline()
while s:
print( s.strip('\r\n') )
s = _file.readline()
</syntaxhighlight>
Notes:
* the file mode ''''r'''' used in the {{fname|open()}} reads text file.
* the {{fname|readline()}} read and return a line from the file (including the carriage return & line feed.
* the {{fname|strip('\r\n')}} remove the carriage return & line feed from the readed line. Otherwise it will also be printed to the REPL (which result into a double line feed).
== File-systems, Writing and data lost ==
{{underline|'''The computer file-system:'''}}
{{underline|'''The computer file-system:'''}}
{{underline|'''SD Card file system:'''}}
{{underline|'''SD Card file system:'''}}
[[Fichier:micro-sd.png|128px]]
Regardless of the platform using the SD card, the content and stability of a SD card is veryyyyyyy sensitive to the open/close operation on the file-system. Users of the Raspberry-Pi nano computer knows that powering of a Pi during SD write operation could completely corrupt the file-system. In some rare situation the SD card can be made completely unreadable.
Regardless of the platform using the SD card, the content and stability of a SD card is veryyyyyyy sensitive to the open/close operation on the file-system. Users of the Raspberry-Pi nano computer knows that powering of a Pi during SD write operation could completely corrupt the file-system. In some rare situation the SD card can be made completely unreadable.
LittleFS is a flash-based device filesystem. It has been designed to be more resistant to filesystem corruption and power failures resilient. Unless other file-systems, the RAM used by LittleFS does not depend on the file-system size (it is said "RAM bounded" without RAM allocation overflow). See [https://github.com/littlefs-project/littlefs LittleFS Github] for more information.
LittleFS is a flash-based device filesystem. It has been designed to be more resistant to filesystem corruption and power failures resilient. Unless other file-systems, the RAM used by LittleFS does not depend on the file-system size (it is said "RAM bounded" without RAM allocation overflow). See [https://github.com/littlefs-project/littlefs LittleFS Github] for more information.
So, even if LittleFS do have some minimal buffering, it is possible to force writing to the flah ( with {{fname|flush()}} ). So the user code can rely on better file-system stability and better control over forced writing operation.
So, even if LittleFS do have minimal buffering, it is possible to force writing to the flash ( with {{fname|flush()}} ) to ensure minimal data lost in case of issue. So the user code can rely on better file-system stability and better control over forced writing operation.
The following example just {{fname|flush()}} writes at every line written to the file.
The following example just {{fname|flush()}} writes at every line written to the file.
[[Fichier:LittleFS-flushed.png|640px]]
[[Fichier:LittleFS-flushed.png|640px]]
== Ressources ==
* [https://docs.micropython.org/en/latest/library/os.html Basic "operating system" services] (''micropython.org'')<br />Usual OS functions + file-system mounting, formating, block devices, etc
* [https://docs.micropython.org/en/latest/reference/filesystem.html Working with filesystems] (micropython.org)
{{ENG-CANSAT-PICO-TRAILER}}
{{ENG-CANSAT-PICO-TRAILER}}