Converting data types

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1

I’m using SdFat to read a text file and extract the data I need on each line by doing this:

    char *fileName = strtok(fileData, "|");
    imgRefresh = atof(strtok(NULL, "|"));
    imgTimeout = atof(strtok(NULL, "|"));
    displayPause = atof(strtok(NULL, "\r"));

After that, I open the file indicated by the ‘fileName’ variable:

myFile.open(fileName, O_READ)

However, I am running into a small snag. If the text file has TABs or spaces in a line, I need to remove those. For example, this line works great:

ff001.led|0|8|0.1

However, if I have:

ff001.led |0|8|0.1

That fails because the filename is now 'ff001.led ’ with the extra space(s). The same applies if it’s a TAB.

I actually want the spaces/TABs in the file, I just need to strip them in my program. So how can I remove them?

2

It is called ‘parsing’ and there are a number of ways to do this which depend on what library string functions your compiler supports. The brute force method is to go through the string one character at a time ans test if the character is a space or tab (or conversely a good character) then write a good character to a new string and skip to the next character if a space or tab.

You compiler may have some useful string functions so read the manual to see what it has and how to use them.

Like wise, do a web search (google) for C language string parsing functions to learn more.

3

The computer would be the GCC that comes with the Arduino IDE.

4

There should be lots of info on the GCC compiler (not computer) available on the web.

I haven’t used it so am unfamiliar with what functions it has in it’s libraries but they should be listed in the string.h header.

5

And you’re right, I was looking at using the String object within the Arduino environment which is where my initial subject line came from, it changes the data type, and I can’t pass it to SD.open anymore. I don’t know how to convert it back.

6

Well, on a desktop PC, I’d probably use a regular expression to parse the line easily, but a quick googling reveals that is still not implemented on gcc. You can try strtok(fileData, "|\t ") – that’s “pipe, tab, space” and that seems like it should work.

7

Ok, that does seem to work, however it fails if there are two TABs one after the other. This would be so much easier with proper regexp … but I digress.