A question about using "fscanf_s" to read data in the txt file.

This is a discussion on A question about using "fscanf_s" to read data in the txt file. within the C Programming forums, part of the General Programming Boards category; Originally Posted by Elysia Do not use atoi/atol; use strtol. Hey Elysia, I used your proposed statement in the following ...

  1. #16
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    Quote Originally Posted by Elysia View Post
    Do not use atoi/atol; use strtol.
    Hey Elysia,

    I used your proposed statement in the following way, i.e.
    Code:
    if (strtol(_temp, NULL, 10)) 		
    {
       number = strtol(_temp, NULL, 10);
    }
    There is no error raised when the value actually exceeds the limitation, instead after the conversion, the value of "number" is "2147483647".

    In above example, _temp is "8729348702983457023894" read from the txt data file.

    Bests,

    Qing

  2. #17
    C++まいる!Cをこわせ! Elysia's Avatar
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    As the manual says, it returns LONG_MAX if an overflow occurs. C functions do not throw errors.
    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.

  3. #18
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    Quote Originally Posted by Elysia View Post
    As the manual says, it returns LONG_MAX if an overflow occurs. C functions do not throw errors.
    What do you mean by "throw errors?" I see no exception handling in the example.

    At any rate, strtol() most certainly does inform you if the value under- or overflowed, by setting errno to ERANGE.

    And many standard functions return special values to indicate "error."

  4. #19
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    Quote Originally Posted by Elysia View Post
    As the manual says, it returns LONG_MAX if an overflow occurs. C functions do not throw errors.
    Hey Elysia,

    Thanks for it.

    I fix the problem, i.e. by using LONG_MAX and LONG_MIN.

    Best,

    Qing

  5. #20
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by brewbuck View Post
    What do you mean by "throw errors?" I see no exception handling in the example.
    It was in response to
    There is no error raised...
    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.

  6. #21
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    I don't know if that was meant to refer literally to the raising/throwing of an exception, but just an indication of error state. The OP can certainly check whether overflow occurred by seeing if errno == ERANGE.

  7. #22
    C++まいる!Cをこわせ! Elysia's Avatar
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    I was referring more to the point that the OP was expecting some "magic" to happen when overflow occurred. Which it obviously doesn't.
    Checking for the error in errno == ERANGE is the error checking, not some "magic".
    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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