I am using a script that takes the arduino serial and writes it to an out.dat file. The scripts works fine when run after boot, however when I added the script to /etc/rc.local it runs the script, but does not record the information

# get lines of text from serial port, save them to a file

from __future__ import print_function
import serial, io
import datetime

addr  = '/dev/ttyACM0'  # serial port to read data from
baud  = 9600            # baud rate for serial port
fname = 'gps-log'+datetime.datetime.now().strftime("%m-%d-%Y %H-%M-%S")+'.dat'   # log file to save data in
fmode = 'a'             # log file mode = append

with serial.Serial(addr,9600) as pt, open(fname,fmode) as outf:
    spb = io.TextIOWrapper(io.BufferedRWPair(pt,pt,1),
        encoding='ascii', errors='ignore', newline='\r',line_buffering=True)
    spb.readline()  # throw away first line; likely to start mid-sentence (incomplete)
    while (1):
        x = spb.readline()  # read one line of text from serial port
        print (x,end='')    # echo line of text on-screen
        outf.write(x)       # write line of text to file
        outf.flush()        # make sure it actually gets written out

Credit to https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=64545

Note, it is supposed to create a new file named after the date and time. When I boot to command line, it prints the serial, so I know the program has executed. However, when I power down there is no .dat file to be found.

1 Answer 1


fname = 'gps-log'+datetime.datetime.now().strftime("%m-%d-%Y %H-%M-%S")+'.dat'

Appears to not involve any path. Where are you expecting to find these files?

I think an init service which does this will default to writing to /, so you could check there. However, you probably want to append an absolute path so you have a better place to store these and find them.

fname = '/var/log/gps/gps-log'+ ....
  • 1
    As @goldilocks points out the file may have been created but not where you are expecting it to be. You can use the find command to check: find / -name '*.py' Commented Apr 12, 2016 at 19:35

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