merging files into one

This is a discussion on merging files into one within the C Programming forums, part of the General Programming Boards category; Hi, I am trying to copy several rtf files into one rtf file. this is basically what i have done ...

  1. #1
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    merging files into one

    Hi,

    I am trying to copy several rtf files into one rtf file. this is basically what i have done

    Code:
    char in_filename[MAXPATHLEN];
    char out_filename[MAXPATHLEN];
    FILE *in_fp, *out_fp;
    char line_buffer[80];
    
    //....get the required file name through user input 
    // assumed they lead to correct files so the program does not
    // crash on incorrect file path
    
    
    if (out_fp = fopen(out_filename, "w")  == '\0')
    {
        printf("error opening file");
        break;
    }
    in_fp = fopen(in_filename, "r");
    while (fgets(line_buffer, 80, in_fp) != NULL)
        fputs(line_buffer, out_fp);
    fclose(in_fp);
    fclose(out_fp);
    but i get a segmentation fault after reading the first line of the file

  2. #2
    Guest Sebastiani's Avatar
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    you have to check the return value of fopen each and every time...never assume that the file can be opened!

    >> if (out_fp = fopen(out_filename, "w") == '\0')

    '\0' is used for representing the ASCII value zero and should only be used with text-based processing - for pointers use 0 or NULL.
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  3. #3
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    That doesnt solve the segmenation fault.

    I can open a new file and open the file to read it.

    it crashes somewhere between the while loop statment.

  4. #4
    Guest Sebastiani's Avatar
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    so you are checking the return value of 'in_fp'? also if the file can't be opened be sure to bypass any calls to fclose on the handle.
    Last edited by Sebastiani; 02-16-2006 at 06:26 PM.
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  5. #5
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    yep... doing the same thing as when i check out_fp

  6. #6
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    I found out what i was doing wrong.

    When i check to see if i can open or read the file i didnt put braces around the openning of the file first.
    Code:
    if (out_fp = fopen(out_filename, "w") == NULL)
    
    /*** should be ***/
    
    if ((out_fp = fopen(out_filename, "w")) == NULL)
    For anyone who is interested.

    Thanks for the help about the '\0' character

  7. #7
    cwr
    cwr is offline
    Registered Luser cwr's Avatar
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    Edit: too late, this post was written before I saw the previous post.

    See my added stuff...

    Quote Originally Posted by mbooka
    Hi,

    I am trying to copy several rtf files into one rtf file. this is basically what i have done

    Code:
    char in_filename[MAXPATHLEN];
    char out_filename[MAXPATHLEN];
    FILE *in_fp, *out_fp;
    char line_buffer[80];
    
    //....get the required file name through user input 
    // assumed they lead to correct files so the program does not
    // crash on incorrect file path
    
    /* Without the added (blue) parentheses, you have a precedence issue, 
        you are assigning out_fp to the comparison result of fopen()'s return and NULL */
    if ((out_fp = fopen(out_filename, "w"))  == /* '\0' WRONG */NULL)
    /* fopen returns NULL on error, this is not the same as '\0' */
    {
        printf("error opening file");
        break;
    }
    in_fp = fopen(in_filename, "r");
    /* check in_fp is not NULL here.  There is no excuse even if you're sure the 
    file exists */
    while (fgets(line_buffer, 80, in_fp) != NULL)
        fputs(line_buffer, out_fp);
    fclose(in_fp);
    fclose(out_fp);
    but i get a segmentation fault after reading the first line of the file
    Last edited by cwr; 02-16-2006 at 06:33 PM.

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