Hello have an array of strings that loads strings from a txt file on an sd card. The txt file on the SD card can change from time to time(not while the Arduino is running).I want to be able to get the amount of elements in the array after the txt file has been loaded into the array. The txt file has lines of txt in it. Each line in the file is put into a string in the array. I want to be able to get the amount of elements in the array how can I do this?

  • This is your third post on basically the same subject. If I attempt to "read-between-the-lines" you are trying to implement a simple shell. You need to rethink how command lines are entered. It is not a very good idea to read the whole file into a vector of strings. Even worse is using the String class. Cheers! Feb 17, 2016 at 12:46

2 Answers 2


You can't. That concept does not exist in C.

An array has a fixed size - as such you know how many elements are in it, since that is the number of elements you created it with.

String myStrings[4];

That is an array of 4 String objects. It has 4 elements. It will always have 4 elements.

  • 1
    so could I set the array size to say 400 and only load 100 lines of text? Feb 17, 2016 at 11:39
  • 2
    If you have the memory to store that kind of thing.
    – Majenko
    Feb 17, 2016 at 11:39

numElements = (sizeof(array) / sizeof(array[0]));

  • This is not working for String array.
    – user_fs10
    Feb 28, 2021 at 6:05

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