Thread: reading a file

hi,
i have a struct that holds variables of different data types. i am trying to read the first character of data from a data file and store the data into the struct..

the file holds data like this:
interger 5
real 6.4
character c

so here is my code:

Code:

/* testCommand.h */


typedef struct {
    char mycom[10];
    int integer;
    double real;
    char character;
}command;

Code:

/* testCommand.c */




#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#include "testCommand.h"


FILE *f;
int main(int argc, char* argv[]){
    int lenght, i;
    char ch;
    command *mycommand = (command*)malloc(sizeof(command));


    f = fopen(argv[1], "r+");
    if( f != NULL){
        lenght = numLine(f);
        printf("Number of Lines: %d\n", lenght);
    
        for(i=0; i<(lenght); i++){
            ch = fgetc(f);    // get the forst character of the command
            if (ch == 'i'){
                fscanf(f, "%s %i", &(mycommand->mycom), &(mycommand->integer));
                printf("%s %i\n", (mycommand->mycom), (mycommand->integer));    
            }
            else if (ch == 'r'){
                fscanf(f, "%s %lf", &(mycommand->mycom), &(mycommand->real));
                printf("%s %i\n", (mycommand->mycom), (mycommand->real));    
            }
            else if (ch == 'c'){
                fscanf(f, "%s %c", &(mycommand->mycom), &(mycommand->character));
                printf("%s %i\n", mycommand->mycom, mycommand->character);    
            }
            
            else {
                printf("Invalid!\n");    
            }        


        }


    }
    
    else{
        perror("couldnt open");    
    }


        return 0;
}


int numLine(FILE* fileNames){
    int numLines=0;
    char ch;
        do{
            ch = fgetc(fileNames);
            if(ch == '\n')
            numLines++;
        } while (ch != EOF);


        if(ch != '\n' && (numLines) != 0){ 
            numLines++;
        }
    return numLines;
}

the program always outputs "Invalid!".

SORRY IF THE QUESTION IS WORDED BADLY.. :/

After numLines finished with the file, the file pointer is at the "end of file" position.
The input functions in the main() function all fail because they have nothing left to read.

You need to either close and re-open the file
or rewind() it back to the beginning (you can also use fseek()).

One of your problems is that you read to the end of the file in your numLine() function, then you never reset the file back to the beginning. Also in numLine() if you use a large enough character buffer you could get the entire line at a time using fgets().

Jim

@qny, thanks that worked... but nowww when i run the program with a file like this:
real 5.5
integer 2
character c

i get an output something like this:
Number of Lines: 3
eal 0
Invalid!
nteger 2

You may want to start by turning up your warnings. When I compiled your code I received these messages:

main.c||In function ‘main’:|
main.c|38|warning: format ‘%s’ expects argument of type ‘char *’, but argument 3 has type ‘char (*)[10]’ [-Wformat]|
main.c|42|warning: format ‘%s’ expects argument of type ‘char *’, but argument 3 has type ‘char (*)[10]’ [-Wformat]|
main.c|43|warning: format ‘%i’ expects argument of type ‘int’, but argument 3 has type ‘double’ [-Wformat]|
main.c|46|warning: format ‘%s’ expects argument of type ‘char *’, but argument 3 has type ‘char (*)[10]’ [-Wformat]|
main.c|23|warning: unused parameter ‘argc’ [-Wunused-parameter]|

Jim

so i fixed those errors,, but i still get the following outputs for an input file that contains the data:
real 5.5
integer 2
character c

OUTPUT:
Number of Lines: 3
eal 5.500000
Invalid!
nteger 2

Originally Posted by m_programmer

@qny, thanks that worked... but nowww when i run the program with a file like this:
real 5.5
integer 2
character c

i get an output something like this:
Number of Lines: 3
eal 0
Invalid!
nteger 2

This is a similar problem.
In the main() function you first read a character into ch; then, based on that, you read the rest of the command.
You can solve it easily by also printing ch.

You're going to have problems with the ENTERs on every line.
The best option to deal with them (using fgets()) is going to force you to make lots of changes to your code. A fast solution is to ignore them right before the instruction that reads the first letter of the command.

Why not just read the entire command string with scanf() instead of just reading the first letter? Then compare the first letter of command to your desired character. Also for any further question please post the modified code.

Jim