Read from file a float

This is a discussion on Read from file a float within the C Programming forums, part of the General Programming Boards category; The contents of the file are: Code: dim 400 epsilon 0.001 .... the code is: Code: // read the dimension ...

  1. #1
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    Read from file a float

    The contents of the file are:
    Code:
    dim 400
    epsilon 0.001
    ....
    the code is:
    Code:
        // read the dimension of the table
        fscanf(fp, "dim %d", &dimension);
        fprintf(stderr, "the dimension is %d\n", dimension);
        //printf("the dimension is %d\n", dimension);
        // read the fault tolerance (epsilon)
        fscanf(fp, "epsilon %f", &eps);
        fprintf(stderr, "epsilon is %f\n", eps);
    It doesn't seem to be working for the float number but works for the integer. What's wrong?

  2. #2
    and the hat of wrongness Salem's Avatar
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    fscanf returns a result, maybe check what that is?

    TBH, use fgets() and sscanf for a more predictable outcome. If fscanf() errors out half-way through a line, you've got no idea where you are.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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    Thanks Salem. Breaking it up into pieces helped me to find the error.
    The fscanf() was reading the new line character and not the next line.
    The code which does the work is:
    Code:
        fscanf(fp, "dim %d", &dimension);
        fprintf(stderr, "the dimension %d\n", dimension);
        getc(fp);
        fscanf(fp, "epsilon %lf", &eps);
        fprintf(stderr, "epsilon is %f\n", eps);

  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
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    Again, it's better to just use fgets. Then you don't have to worry about crap stuck in the input buffer.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  5. #5
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    I'll keep it in mind Elysia.
    Isn't there any speed trade-off using these two statements instead of one?

  6. #6
    C++まいる!Cをこわせ! Elysia's Avatar
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    You hardly need to worry about the performance.
    If performance is low, then you would use a profiler to find the real bottleneck, which may or maybe not be what you think it is.
    Don't worry about optimization prematurely.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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