Variable file names with fopen function?

This is a discussion on Variable file names with fopen function? within the C Programming forums, part of the General Programming Boards category; Hi all, I was wondering if it possible to have a varying name for the filename as part of the ...

  1. #1
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    Variable file names with fopen function?

    Hi all,
    I was wondering if it possible to have a varying name for the filename as part of the fopen function with the filename being supplied by Command Line Argument. Off the top of my head I would say yes but that would mean that the filename would have to be in the same place everytime otherwise it wouldnt work. What are your thoughts? My thoughts are that it woul look something like this;

    Assuming the filename is in the last position

    char filename=(argc-1);

    <intermittant code>

    FILE *fopen(const char *filename, const char *r);

    Would this work? Just curious because I may have to implement it

    Alex

  2. #2
    Eager young mind
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    yeah ,its definitely possible..

    U can think of doing something like :

    Code:
     int main(int argc, char  *argv[])
     {
     char filename[SIZE];
     FILE *fp;
      ...
      argv++; 
     strcpy(filename, *argv);
     
      ..
      fp=fopen(filename , "r");
      ...
     return 0; 
    }
    Last edited by kris.c; 07-25-2006 at 08:14 AM.

  3. #3
    Frequently Quite Prolix dwks's Avatar
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    You can pass a variable to fopen, you don't have to hard-code the name into your program.

    Code:
    char filename=(argc-1);
    You mean this, right?
    Code:
    strcpy(filename, argv[argc-1]);
    [edit]
    Code:
      argv++; 
     strcpy(filename, *argv);
    Why increment argv? You can just use argv[1].
    [/edit]
    dwk

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  4. #4
    and the hat of wrongness Salem's Avatar
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    I wonder what's wrong with
    fp = fopen( argv[1], "r" );

    Why all the unnecessary copying of the filename to a temporary.
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  5. #5
    int x = *((int *) NULL); Cactus_Hugger's Avatar
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    Er... why strcpy()...? Just:
    Code:
    fopen(argv[1], "r");
    And:
    Code:
    strcpy(filename, argv[argc-1]);
    If I enter no commandline arguments, you'll be opening the executable.
    long time; /* know C? */
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  6. #6
    Frequently Quite Prolix dwks's Avatar
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    It was assumed that you would check for argc to be > 1.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
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