Reading one line at a time...

This is a discussion on Reading one line at a time... within the C Programming forums, part of the General Programming Boards category; Well why do I always get "Couldn't open somefile.txt"? Code: #include <stdio.h> #define MAX_LINE_LENGTH 256 int main(int argc, char *argv[]) ...

  1. #1
    the magic penguim
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    Jul 2005
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    91

    Reading one line at a time...

    Well why do I always get "Couldn't open somefile.txt"?

    Code:
    #include <stdio.h>
    #define MAX_LINE_LENGTH 256
    
    int main(int argc, char *argv[])
    {
        if(argc != 2)
        {
             printf("Input should be of the form \'line filename.txt\'");
    	 return 1;
        }
    
        FILE *fp = fopen("argv[1]", "r");
        if(fp == NULL)
        {
            printf("Couldn't open %s", argv[1]);
    	return 1;
        }
        
        char line[MAX_LINE_LENGTH + 1];
    
        while(fgets(line, MAX_LINE_LENGTH, fp) != NULL)
        {
            printf(line);
        }
        return 0;
    }
    The file is there, so the problem isn't it...
    Last edited by lala123; 07-07-2005 at 03:01 PM.

  2. #2
    Griz803 Griz803's Avatar
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    Hi, maybe you'd wanna try taking the double qoutes away from the expression argv[1] in the call to fopen. You don't want to open a file named argv[1] as a literal string, you want to open the value in argv[1] itself. Hope this helps.

  3. #3
    the magic penguim
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    Oh thanks

    But now I have another problem...

    Code:
        while(fgets(line, 256, fp) != NULL)
        {
            if(strcmp(line, argv[2]) == 0)
            {
                printf("%s", line);
                fclose(fp);
                return 0;
            }
        }
    I wan't to compare the second argument argv[2] with the current line, but why do I always get no matches when they do match?

  4. #4
    Code Goddess Prelude's Avatar
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    >but why do I always get no matches when they do match?
    Because fgets takes the newline character with it. You can remove the newline any number of ways, but the common favorite is:
    Code:
    char *newline = strchr ( line, '\n' );
    
    if ( newline != NULL )
      *newline = '\0';
    However, I was always partial to this one because of its sheer cleverness:
    Code:
    line[strcspn ( line, "\n" )] = '\0';
    My best code is written with the delete key.

  5. #5
    the magic penguim
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    Thanks Works fine now.

  6. #6
    the magic penguim
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    Hm... What's wrong with this line:

    Code:
    char *PrintMD5(UCHAR md5Digest[16]);
    I'm getting:

    Code:
    syntax error before "md5Digest"

  7. #7
    Just Lurking Dave_Sinkula's Avatar
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    Well, what's before md5Digest? UCHAR perhaps? That isn't a keyword, so where might you find it defined?
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  8. #8
    the magic penguim
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    Well I don't know... I hate using other people's code... Do you know a MD5 code that has no errors?

  9. #9
    and the hat of wrongness Salem's Avatar
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    > Do you know a MD5 code that has no errors?
    Or even a user who has a clue about porting code perhaps?

    Look at it again
    Then decide whether
    typedef unsigned char UCHAR;
    is perhaps the right thing to do
    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.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  10. #10
    Registered User
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    Quote Originally Posted by lala123
    Do you know a MD5 code that has no errors?
    check this site. Click the E-Security link in left pane. It has a link for MD5 code with explaination.

  11. #11
    the magic penguim
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    Okay, I added:

    Code:
    typedef unsigned char UCHAR;
    typedef unsigned int UINT;
    But now I'm getting lots of undefined variables here:

    Code:
    static inline void FF(UINT& a, UINT b, UINT c, UINT d, UINT x, UINT s, UINT ac){ a += F(b, c, d) + x + ac; a = rotate_left(a, s); a += b; }
    static inline void GG(UINT& a, UINT b, UINT c, UINT d, UINT x, UINT s, UINT ac){ a += G(b, c, d) + x + ac; a = rotate_left(a, s); a += b; }
    static inline void HH(UINT& a, UINT b, UINT c, UINT d, UINT x, UINT s, UINT ac){ a += H(b, c, d) + x + ac; a = rotate_left(a, s); a += b; }
    static inline void II(UINT& a, UINT b, UINT c, UINT d, UINT x, UINT s, UINT ac){ a += I(b, c, d) + x + ac; a = rotate_left(a, s); a += b; }

  12. #12
    ATH0 quzah's Avatar
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    Well for starters, you're compiling C++ code. Notice the keyword inline? Also notice the use of references (UINT& a, ...).


    Quzah.
    Hope is the first step on the road to disappointment.

  13. #13
    the magic penguim
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    Thanks. Got it now.

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