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In order to make an algorithm work, I'd like to delete the first line of a text file. I'm having a hard time finding an example for that though. I was thinking that there should be the possibility to delete up to a \n. Could you point me to a solution? Oh, I'm using a standard Arduino Uno

Thank you

  • Is it necessary to re-write the file, or is this a file whose later contents will be read and processed by the Arduino? If the latter, then you can just read and throw away a character at a time until you get to '\n' after you open the file. – jose can u c Apr 3 '18 at 14:30
  • Well, in this case, the Arduino is connected to Wifi and serves each produced data point as a .csv to a server. I suppose this counts as "processing by Arduino". So what you suggest would work. I'm not sure though how one would go about to "throw away a character". Is there a search term for that, so I can check it out? Thanks! – user3465376 Apr 4 '18 at 7:45
  • To read the file, you would use fopen() to open it and get a file handle. Then you use fgetc() to read one character at a time and check that character to see if it's '\n'. By "throwing away", I mean that the character you read can just be overwritten by the next one you read -- you don't have to build a string or anything or try to save the character for later in the program. – jose can u c Apr 4 '18 at 12:35
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What you can do is:

  • opening a file (to read)
  • opening a new file (to write)
  • since a line can be long (more than arduino's memory), it's best to read it character by character, thus:
  • use a boolean to denote when to start removing a line (set to e.g. Remove = TRUE)
  • For every character you read:
    • If Remove is TRUE, don't write to the output file, otherwise write it
    • If the character is \n or \r (check how line ends are), set the boolean to False (e.g. continue writing)
  • Remove file to read
  • Rename written file
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