File System¶
FileSystem is a subclass of
EV3. It uses system commands and allows to
operate on EV3’s file system (read LEGO’s Communication Developer Kit
for the details). You can read, write and delete files and
directories. Please take care, you can damage the software of your EV3
brick.
Method list_dir¶
Connect your EV3 brick and your computer with an USB cable. Replace the MAC-address by the one of your EV3 brick, then start this program:
import ev3_dc as ev3
my_ev3 = ev3.FileSystem(
protocol=ev3.USB,
host='00:16:53:42:2B:99',
)
def print_header(type: str):
print()
if type == 'rsf':
print('robot sound file size (bytes) md5-checksum')
elif type == 'rgf':
print('robot graphics file size (bytes) md5-checksum')
elif type == 'rbf':
print('robot brick file size (bytes) md5-checksum')
print('-'*75)
def print_table(files: tuple, type: str):
header_printed = False
for file in files:
if file[0].endswith('.' + type):
if not header_printed:
print_header(type)
header_printed = True
print(
'{:27s} {:12d} {:12s}'.format(*file)
)
folders, files = my_ev3.list_dir('/home/root/lms2012/sys/ui')
print_table(files, 'rsf')
print_table(files, 'rgf')
print_table(files, 'rbf')
Some remarks:
- This program reads files and subfolders in directory /home/root/lms2012/sys/ui. Then it prints the sound-, graphics- and brick-files as tables.
- The operating system of the EV3 brick is Unix, therefore use slashes, not backslashes when writing the path of a directory.
- You can use absolute or relative paths, releative paths are relative to /home/root/lms2012/sys, e.g. our path could also be written as ./ui.
- files is a tuple of tuples. Per file, we get three data:
- name of the file,
- size of the file,
- md5 checksum of the file’s data.
- We ignore subfolders, because in this directory, there is none.
The output:
robot sound file size (bytes) md5-checksum
---------------------------------------------------------------------------
Startup.rsf 3109 7BE0A201F57917BC0DDE508E63DD7AD8
PowerDown.rsf 7939 2381EF46C5166BFF0B5852369E5A2CC7
OverpowerAlert.rsf 8553 BE802DF67CBBC4E4A40C223BFFF4C14A
GeneralAlarm.rsf 7300 A40C190AF86C8FA9A7FE9143B36B86EC
DownloadSucces.rsf 6599 681C88B5930DE152C0BB096F890C492F
Click.rsf 173 A16F9F1FDDACF56EDF81B4CD968826B4
robot graphics file size (bytes) md5-checksum
---------------------------------------------------------------------------
settings_screen.rgf 600 55186477FDBAF838AEDA09BFDBFAABA2
screen.rgf 2049 ACE80443D1FA8736231BA21D63260CA4
playrecent_screen.rgf 600 CDBAE801B780484D80DA95538CF867C2
mindstorms.rgf 302 BCED9CC85FCB72259F4901E836AED8DF
file_screen.rgf 600 EFF6FAE6C487828734800AFB912DD700
apps_screen.rgf 600 19EA377DAD1869512B3759E28B6DECCD
Ani1x.rgf 42 AB225E46367E84D5FC23649EC4DE1CE9
144x82_POP4.rgf 1478 7E255363590442E339F93CBDAF222CA1
144x65_POP3.rgf 1172 2BED43A3D00A5842E4B91E136D232CEA
robot brick file size (bytes) md5-checksum
---------------------------------------------------------------------------
ui.rbf 5030 6F46636743FBDE68B489071E590F0752
Now we come to directories. The following program demonstrates, how to recursively read a directory subtree.
import ev3_dc as ev3
my_ev3 = ev3.FileSystem(
protocol=ev3.USB,
host='00:16:53:42:2B:99',
)
def dir_recursive(path: str):
folders, files = my_ev3.list_dir(path)
for folder in folders:
if folder in ('.', '..'):
continue
next_path = path + '/' + folder
print(next_path)
dir_recursive(next_path)
dir_recursive('/home')
This program recursively reads the /home folder, where Unix systems hold the user-owned data. It prints all subfolders, but ignores files inside the folders.
The output:
/home/root
/home/root/lms2012
/home/root/lms2012/tools
/home/root/lms2012/tools/WiFi
/home/root/lms2012/tools/Volume
/home/root/lms2012/tools/Sleep
/home/root/lms2012/tools/Brick Info
/home/root/lms2012/tools/Bluetooth
/home/root/lms2012/sys
/home/root/lms2012/sys/ui
/home/root/lms2012/sys/settings
/home/root/lms2012/sys/mod
/home/root/lms2012/sys/lib
/home/root/lms2012/source
/home/root/lms2012/prjs
/home/root/lms2012/prjs/BrkProg_SAVE
/home/root/lms2012/prjs/BrkProg_SAVE/CVS
/home/root/lms2012/apps
/home/root/lms2012/apps/Brick Program
/home/root/lms2012/apps/Brick Program/CVS
/home/root/lms2012/apps/IR Control
/home/root/lms2012/apps/IR Control/CVS
/home/root/lms2012/apps/Port View
/home/root/lms2012/apps/Port View/CVS
/home/root/lms2012/apps/Motor Control
/home/root/lms2012/apps/Motor Control/CVS
Some remarks:
- root is the only user on this Unix system.
- If you already worked on some projects and did run them on your EV3 brick, you will find them in /home/root/lms2012/prjs.
- The sequence of subfolders is backward-sorted by name as is the sequence of files.
Method create_dir¶
Method create_dir() allows to create
directories in the filesystem of the EV3 brick.
Connect your EV3 brick and your computer with an USB cable. Replace the MAC-address by the one of your EV3 brick, then start this program:
import ev3_dc as ev3
my_ev3 = ev3.FileSystem(
protocol=ev3.USB,
host='00:16:53:42:2B:99',
)
dir = '/home/root/lms2012/prjs'
subdir = 'tmp'
# read sub-directories
folders, files = my_ev3.list_dir(dir)
print('*** old ***')
for folder in folders:
print(folder)
# create directory
my_ev3.create_dir(dir + '/' + subdir)
# read sub-directories
folders, files = my_ev3.list_dir(dir)
print('*** new ***')
for folder in folders:
print(folder)
This program first reads the sub-directories of /home/root/lms2012/prjs, then it creates directory /home/root/lms2012/prjs/tmp and finally it again reads the sub-directories of /home/root/lms2012/prjs.
There are a lot of restrictions for user root’s filesystem. E.g. you are not allowed to create sub-directories in /home/root or /home/root/lms2012. If you try to do that, the EV3 brick answers with an error.
The output:
*** old ***
BrkProg_SAVE
..
.
*** new ***
BrkProg_SAVE
tmp
..
.
Indeed, after creating directory /home/root/lms2012/prjs/tmp there is an additional sub-directory named tmp in /home/root/lms2012/prjs.
If you start this program a second time, you will get an error because you can’t create a directory that allready exists.
Method del_dir¶
Method del_dir() allows to delete
directories in the filesystem of the EV3 brick.
Connect your EV3 brick and your computer with an USB cable and replace the MAC-address by the one of your EV3 brick. The following program is thought to be executed after the one above:
import ev3_dc as ev3
my_ev3 = ev3.FileSystem(
protocol=ev3.USB,
host='00:16:53:42:2B:99',
)
dir = '/home/root/lms2012/prjs'
subdir = 'tmp'
# read sub-directories
folders, files = my_ev3.list_dir(dir)
print('*** old ***')
for folder in folders:
print(folder)
# delete directory
my_ev3.del_dir(dir + '/' + subdir)
# read sub-directories
folders, files = my_ev3.list_dir(dir)
print('*** new ***')
for folder in folders:
print(folder)
The program is very similar to the one above, but it deletes a directory instead of creating it.
The output:
*** old ***
BrkProg_SAVE
tmp
..
.
*** new ***
BrkProg_SAVE
..
.
Indeed, after deleting directory /home/root/lms2012/prjs/tmp there is no more a sub-directory named tmp in /home/root/lms2012/prjs.
And again, you can’t run this program a second time. If you do so, you will get an error because you can’t delete a directory that doesn’t exist.
If you need to delete non-empty directories, setting keword argument secure=False allows to do so.
Method read_file¶
Connect your EV3 brick and your computer with an USB cable. Replace the MAC-address by the one of your EV3 brick, then start this program:
import ev3_dc as ev3
from hashlib import md5
my_ev3 = ev3.FileSystem(
protocol=ev3.USB,
host='00:16:53:42:2B:99',
)
folder = '/bin'
filename = 'usb-devices'
# read data from EV3 brick, calculate md5 and write data to local file
data = my_ev3.read_file(folder + '/' + filename)
print('md5-checksum (copy):', md5(data).hexdigest().upper())
with open(filename, 'w') as f:
f.write(data.decode('utf-8'))
# get md5 of the file from EV3 brick
subfolders, files = my_ev3.list_dir(folder)
for file in files:
if file[0] == filename:
print('md5-checksum (orig):', file[2])
This program reads file /bin/usb-devices from the EV3 brick and writes a local copy. The file is part of the brick’s operating system. It’s human readable because it is a bash-script. The correctness of the reading is demonstrated by two md5-checksums, one from the original on the EV3 brick, the other from the read data.
The output:
md5-checksum (copy): 5E78E1B8C0E1E8CB73FDED5DE384C000
md5-checksum (orig): 5E78E1B8C0E1E8CB73FDED5DE384C000
Method write_file¶
Connect your EV3 brick and your computer with an USB cable. Replace the MAC-address by the one of your EV3 brick and start the following program, that creates sub-directory and a file on the EV3 brick. It writes some text into the file and it allows to test if the md5-checksum is the correct one.
import ev3_dc as ev3
from hashlib import md5
my_ev3 = ev3.FileSystem(
protocol=ev3.USB,
host='00:16:53:42:2B:99',
)
dir = '/home/root/lms2012/prjs'
subdir = 'tmp'
filename = 'some.txt'
txt = 'This is some text.'
txt_bytes = txt.encode('utf-8')
# md5-ckecksum of txt
print('md5-checksum (text):', md5(txt_bytes).hexdigest().upper())
# create directory
my_ev3.create_dir(dir + '/' + subdir)
# write txt into file
my_ev3.write_file(
dir + '/' + subdir + '/' + filename,
txt_bytes
)
# md5-checksum of file
folders, files = my_ev3.list_dir(dir + '/' + subdir)
print('md5-checksum (file):', files[0][2])
# delete directory
my_ev3.del_dir(dir + '/' + subdir, secure=False)
Some remarks:
- Method write-file accepts bytes not str, therefore we need to encode the text.
- Setting secure=False allows to delete the subdirectory with its content. This is done at the end of the program.
The output:
md5-checksum (text): 5A42E1F277FBC664677C2D290742176B
md5-checksum (file): 5A42E1F277FBC664677C2D290742176B
Method copy_file¶
Connect your EV3 brick and your computer with an USB cable. Replace the MAC-address by the one of your EV3 brick and start the following program:
import ev3_dc as ev3
my_ev3 = ev3.FileSystem(
protocol=ev3.USB,
host='00:16:53:42:2B:99',
)
dir = '../prjs/tmp'
filename = dir + '/' + 'some.txt'
filename_copy = dir + '/' + 'copy.txt'
txt = 'This is some text.'
# create directory
my_ev3.create_dir(dir)
# write txt into file
my_ev3.write_file(filename, txt.encode('utf-8'))
# copy file
my_ev3.copy_file(filename, filename_copy)
# read directory's content
folders, files = my_ev3.list_dir(dir)
print('file size (bytes) md5-checksum')
print('-'*75)
for file in files:
print(
'{:27s} {:12d} {:12s}'.format(*file)
)
# delete directory
my_ev3.del_dir(dir, secure=False)
Some remarks:
- This program works with relative paths.
- As above it creates a sub-directory /home/root/lms2012/prjs/tmp.
- File /home/root/lms2012/prjs/tmp/some.txt is created by method
write_file(), file /home/root/lms2012/prjs/tmp/copy.txt is created by methodcopy_file().
The output:
file size (bytes) md5-checksum
---------------------------------------------------------------------------
some.txt 18 5A42E1F277FBC664677C2D290742176B
copy.txt 18 5A42E1F277FBC664677C2D290742176B
As expected, both files have the same sizes and md5-checksums.
Method del_file¶
Method del_file() allows to delete single
files in the file-system of an EV3 brick. Be careful, when using it,
you can even delete files of the EV3 brick’s operating system.
Connect your EV3 brick and your computer with an USB cable. Replace the MAC-address by the one of your EV3 brick and start the following program:
import ev3_dc as ev3
my_ev3 = ev3.FileSystem(
protocol=ev3.USB,
host='00:16:53:42:2B:99',
)
dir = '../prjs/tmp'
filename = dir + '/' + 'some.txt'
filename_copy = dir + '/' + 'copy.txt'
txt = 'This is some text.'
# create directory
my_ev3.create_dir(dir)
# write txt into file
my_ev3.write_file(filename, txt.encode('utf-8'))
# copy file
my_ev3.copy_file(filename, filename_copy)
# delete file
my_ev3.del_file(filename)
# read directory's content
folders, files = my_ev3.list_dir(dir)
print('file size (bytes) md5-checksum')
print('-'*75)
for file in files:
print(
'{:27s} {:12d} {:12s}'.format(*file)
)
# delete directory
my_ev3.del_dir(dir, secure=False)
The program is very similar to the one above. It uses nearly all
methods of class FileSystem.
file size (bytes) md5-checksum
---------------------------------------------------------------------------
copy.txt 18 5A42E1F277FBC664677C2D290742176B
File some.txt has been deleted, only the copy did exist, when
list_dir() was called.