Thread: Read/Write hex from/to a file in C?

  1. #1
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    Read/Write hex from/to a file in C?

    Hello

    I've googled this but I'm not getting much joy.

    Does anyone know of an easy way to read/write hex from/to a file in C?

    Thank you.

  2. #2
    Hurry Slowly vart's Avatar
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    fscanf(f, "%x", &var); maybe
    All problems in computer science can be solved by another level of indirection,
    except for the problem of too many layers of indirection.
    David J. Wheeler

  3. #3
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    Thank you for your reply.

    So if I have a text file called plaintext.txt with the following HEX:

    0123456789ABCDEF

    Should the following code work?

    Code:
    FILE *fp;
    unsigned char message[8];
    
    fp=fopen("c:\\plaintext.txt", "r");
    fscanf(fp, "%x", &message);
    fclose(fp);
    Thank you
    Last edited by MrSteve; 03-25-2008 at 04:30 PM.

  4. #4
    Hurry Slowly vart's Avatar
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    Should the following code work?
    no...
    read the scanf format description
    read about %x format
    read about maximum integer value
    try to figure out your problems...
    All problems in computer science can be solved by another level of indirection,
    except for the problem of too many layers of indirection.
    David J. Wheeler

  5. #5
    Nub SWE
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    Here is the code, like yours, but it compiles:

    Code:
    #include <stdio.h>
    
    int main(void)
    {
    	FILE *fp;
    	unsigned int message;
    
    	fp=fopen("c:\\plaintext.txt", "r");
    	fscanf(fp, "%x", &message);
    	printf("%x ", message);
    	
    	fclose(fp);
    	
    	return 0;
    }
    Here is the output:
    Code:
    89abcdef
    Go from there. Looks to me like it's only printing the last 8 digits.

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