Reading from File

This is a discussion on Reading from File within the C Programming forums, part of the General Programming Boards category; I am trying to figure out how to read formatted input from a file. If this were C++, I would ...

  1. #1
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    Reading from File

    I am trying to figure out how to read formatted input from a file. If this were C++, I would use getline to read a line of the file and then pass that line to a stringstream. But this is the first time I am doing file I/O in C and I am stuck.

    For example, the file would be in the form of:

    Some Picture
    4 3
    128 128
    jpg
    jpeg
    12 3 8 5 4 11 7 1 9 6 10 2

    The first line is a character string.
    the next two lines are integers separated by a tab.
    The next two lines are strings.
    The last line are integers separated by spaces.

    I have the following so far, but it looks like it only reads one string from the line at a time and if it encounters the integers, it may crash since it was expecting a string.:

    Code:
    FILE  *INFILE;
    gchar str [80];
         
    INFILE = fopen (appState->fileName, "r");
        
         while(INFILE)
         {
              fscanf (INFILE, "%s", str);
    Is there a way to do something like the istringstream? Thanks.

  2. #2
    Registered User ssharish2005's Avatar
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    I would use getline to read a line of the file and then pass that line to a stringstream
    You could still use the same tech. Use fgets in C. And perhaps to parse the string use sscanf function.

    ssharish

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    Quote Originally Posted by ssharish2005 View Post
    You could still use the same tech. Use fgets in C. And perhaps to parse the string use sscanf function.

    ssharish
    Thanks for your help, that did it.

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    One of the lines in the file will always contain only 12 integers. How can I loop the following code to insert each integer read into an array.

    Code:
    sscanf (line, "%d %d %d %d %d %d %d %d %d %d %d %d", &img1, &img2,  &img3,  &img4, 
                                                                                                &img5, &img6,  &img7,  &img8,     
                                                                                                &img9, &img10, &img11, &img12);
    Again, in C++ I would have written something like:

    Code:
    while(iss >> anInteger)
    {
      intVector.push_back(anInteger);
    }

  5. #5
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    I am now writing another program, but have a similar question about sscanf. I want to read a line from a file in the form:

    lastname firstname, 123 Fake ST, 1 , Somewhere, US, 0000

    My problem is that sscanf ignores and reads until whitespace is reached, so if I want a string with "lastname firstname" it looks like I will have to have various tmp strings and concatenate them using strcat.

    Is there a way to ignore the whitespace and read up to a comma instead? Thanks.

  6. #6
    CSharpener vart's Avatar
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    "%[^,]"
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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    I have been trying several different things, but have been unable to extract the data from the file correctly. I printed the return value of sscanf, and it read only 1 string from the line. So the format specifier %[^,] reads a string up to a comma, but it seems that it does not continue reading after it encounters a comma. Could someone provide a hint on how to continue reading the entire comma separated line? Thanks.

    Code:
        FILE  *INFILE;
        
        INFILE = fopen (application->fileName, "r");
     
        while( fgets(line, 200, INFILE) != NULL)  
       {
                      sscanf (line, "%[^,] %[^,] %[^,] %[^,] %[^,] %[^,] %[^,]  %[^,] %[^,] %[^,] %[^,]" ,  tmpName,
            										                                                                tmpGroup,
             										                                                                tmpStreet,
                
                                                 //.......................

  8. #8
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    I found a solution and will post in case someone else encounters the same issue.

    Add a %*c to read but not store the comma in between the fields.

    Code:
     sscanf (line, "%[^,] %*c %[^,]

  9. #9
    CSharpener vart's Avatar
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    if you know that there is comma that you need to skip - just write it
    sscanf (line, "%[^,],%[^,]
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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