read from .txt file & put into array?

This is a discussion on read from .txt file & put into array? within the C Programming forums, part of the General Programming Boards category; oops! I sent this to c# accidently, am I guilty of multiple posts with my first post? read from .txt ...

  1. #1
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    read from .txt file & put into array?

    oops! I sent this to c# accidently, am I guilty of multiple posts with my first post?

    read from .txt file & put into array?
    Could someone give me a clue how to read a list of names (one per line )from a text file into an array (2d?) for use in a function.
    I can open and close the file Ok. The file was written to with fprintf and I am trying to read from it with fscanf (using &) but my program keeps crashing. Heres a bit of it below

    //function( ) simply prints the correct answer
    {
    FILE *f;
    char s[30][100]; //crashing badly
    int i;
    f = fopen(datafile,"r"); //../correct_answers.txt
    for(i=0;i!=EOF;i++) //strcpy????
    s[i] = fscanf(f,"\n%s",&s) ;

    switch (theQuestion)
    {
    case 1:

    printf("\n%s",s[0]);//doesn't work

    printf("rrrrr"); //this works but I need
    //the answer from the file in here

    break;
    case 2:

    printf("\n%s",s[1]);
    break;

    The .txt file is as follows:-
    Wilfred Owen
    Jane Austen
    Patrick White



    The program is a CGI program and when invoked from the form
    crashes. It works ok if I use string constants in the case statements but I cant get my answers from the text file into the case statements. I'm new to this, lost , lonely and confused.
    Any clues to point me in the right direction would be much appreciated.
    Thank you.

  2. #2
    Code Goddess Prelude's Avatar
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    >f = fopen(datafile,"r");
    Always test that the file is open.

    >for(i=0;i!=EOF;i++)
    A better way would be to use an input function as the loop condition.

    >s[i] = fscanf(f,"\n%s",&s) ;
    fscanf returns the number of characters read as an integer, s[i] is a character array. You also try to pass the address of a char (*)[100] to fscanf where it expects just a char *.

    Try something like this instead:
    Code:
    if ( ( f = fopen ( datafile, "r" ) ) == NULL ) {
      perror ( "File open falure" );
      exit ( EXIT_FAILURE );
    }
    
    for ( i = 0; fgets ( s[i], sizeof s[i], f ) != NULL; i++ ) {
      /*
      ** Work with the line from the file.
      */
    }
    -Prelude
    My best code is written with the delete key.

  3. #3
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    prelude ,your code works!!

    I stuck an else onto it and put the switch into the body of the loop and it works. Not quite perfect yet since it prints the correct answer three times, four times, five times but I can work on this.
    Thank you for your time *100

  4. #4
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    oops again!
    I took the switch out of the loop and this works perfectly.
    Not entirely sure why it needs the empty curly braces after the for loop but it won't work without them.
    Thanks again.

    ///// ok now
    void cor_ans(int Question)
    {
    FILE *f;
    char s[30][100];
    int i;
    if ( ( f = fopen ( datafile, "r" ) ) == NULL )
    {
    printf ("File open falure" );
    exit ( EXIT_FAILURE );
    }
    else
    for ( i = 0; fgets ( s[i], sizeof s[i], f ) != NULL; i++ ) {

    }


    switch (theQuestion)
    {
    case 1:

    printf("%s",s[0]);

    break;
    case 2:

    printf("%s",s[1]);
    break;
    case 3:
    printf("%s",s[2]);
    break;

  5. #5
    End Of Line Hammer's Avatar
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    6,231
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  6. #6
    Registered User Vber's Avatar
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    for ( i = 0; fgets ( s[i], sizeof s[i], f ) != NULL; i++ ) {

    }
    You can change this to:
    Code:
     for ( i = 0; fgets ( s[i], sizeof s[i], f ) != NULL; i++ ) 
        ;
    You don't need nothing in the loop, because all your work is done there, you catch the text and check if you aren't in the end of the file.

  7. #7
    Me want cookie! Monster's Avatar
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    Originally posted by Vber
    You can change this to:
    Code:
     for ( i = 0; fgets ( s[i], sizeof s[i], f ) != NULL; i++ ) 
        ;
    Even better:
    Code:
    nof_elems = sizeof s / sizeof s[0];
    for ( i = 0; ( fgets ( s[i], sizeof s[i], f ) != NULL ) && ( i < nof_elems ) ; i++ )

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