a really stupid question

I just learned C this morning and I have a simple question. I have a program called donut.c and the code is like this:

Code:

---

#include <stdio.h>

int main()
{
    float dozen_donut_cost;
    int donuts_eaten;
    int i = 0;
    float donuts_cost;

    return 0;
}

---

then when I want to execute donut, the instruction is:
./donut < t0

where the file t0 contains:
3.00 12 .5 .5 .5 .5 .5 .75 .75 .75 .75 1.0 1.0 1.0

how do I assign the variable dozen_donut_cost so that it equals 3.00? Which is the first value in file?? Thanks

Quote:

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Originally Posted by -EquinoX-

I just learned C this morning...

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Don't you mean you started to learn about C this morning?

Quote:

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Originally Posted by -EquinoX-

how do I assign the variable dozen_donut_cost so that it equals 3.00? Which is the first value in file?? Thanks

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Before you can do that, you'll need to keep learning for a while longer.
You need to learn about accepting arguments from the command line into the main function.
You need to learn about pointers and FILE pointers
You need to learn about opening files in different diverse modes
You need to learn how to read from files.
You need to learn how to close files.

That's only a rough road map. Keep it up.

Quote:

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Originally Posted by Aia

Don't you mean you started to learn about C this morning?

Before you can do that, you'll need to keep learning for a while longer.
You need to learn about accepting arguments from the command line into the main function.
You need to learn about pointers and FILE pointers
You need to learn about opening files in different diverse modes
You need to learn how to read from files.
You need to learn how to close files.

That's only a rough road map. Keep it up.

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Say that I want to do this instead of the one that I posted up:
./donut 3.00 12 .5 .5 .5 .5 .5 .5 .75 .75 .75.75

how do I read the 3.0??

Learn C better first before you start messing with things above your head.

Quote:

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Say that I want to do this instead of the one that I posted up:
./donut 3.00 12 .5 .5 .5 .5 .5 .5 .75 .75 .75.75

how do I read the 3.0??

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Well something like this should work:

Code:

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int main(int argc, char* argv[])
{
    int i;
    for(i=0; i<argc; i++)
        printf("&#37;s\n", argv[i]);
    getchar();
}

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basically argc is the number of things you add in the command line, and argv is an array of arguments passed in as a string.

Then you would have to convert the strings to doubles. So look up strtod.

Good luck ;)

But start i at 1 (as mike_g knows of course!).
Element 0 is the program name.

http://faq.cprogramming.com/cgi-bin/...&id=1043284392

but I can't convert the char to an int right??

Quote:

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Originally Posted by -EquinoX-

but I can't convert the char to an int right??

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Oh, oh, here starts to be noticeable the gap in understanding.
Is is not a char. It is a string made up of an array of chars terminated with the nul terminator '\0'.
And yes, you can convert char to int.
Nevertheless, you need to convert the string or array of chars to a float.

http://www.cplusplus.com/reference/c...dlib/atoi.html

I tried to put in this code:

Code:

---

int main(int argc, char* argv[])
{
    int i;
    for(i=0; i<argc; i++)
        printf("&#37;s\n", argv[i]);
    getchar();
}

---

however when I enter the command :
gcc -ansi -Wall donut.c -o donut
./donut < t0

it stays and do nothing, it should print the value of 3.00 12 .5 .5 .5 .5 .5 .75 .75 .75 .75
right? however when I type in
./donut 3.00 12 .5 .5 .5 .5 .5 ..... it works

Quote:

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Originally Posted by -EquinoX-

t should print the value of 3.00 12 .5 .5 .5 .5 .5 .75 .75 .75 .75
right?

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Riiiight!. Your compiler is broken. Make sure you return it for a refund ;)

Just joking.

If anything your program would display:

Quote:

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donut
<
t0

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because that would be argv[0], argv[1] and argv[2].
However that's not the case, since the < is a selected operator by the shell. So any thing after that doesn't count as argument for main.
The point is that it would never display the content of the file t0 that you are passing.

Try:

Code:

---

#include <stdio.h>

int main ( void )
{
        char buf[BUFSIZ];

        while( fgets( buf, sizeof buf, stdin ) )
        {
                printf( "%s", buf );
        }

        return 0;
}

---

and see what happens.

Quote:

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Originally Posted by Aia

Riiiight!. Your compiler is broken. Make sure you return it for a refund ;)

Just joking.

If anything your program would display:

because that would be argv[0], argv[1] and argv[2].
However that's not the case, since the < is a selected operator by the shell. So any thing after that doesn't count as argument for main.
The point is that it would never display the content of the file t0 that you are passing.

Try:

Code:

---

#include <stdio.h>

int main ( void )
{
        char buf[BUFSIZ];

        while( fgets( buf, sizeof buf, stdin ) )
        {
                printf( "&#37;s", buf );
        }

        return 0;
}

---

and see what happens.

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This is what I want, but I don't want it to be printed I want to store each element in the file into an argument. How do I do this?

anyone know how to convert a char into an int of it's value? Say I have a char 15 and I want to get an int which value is 15?

Code:

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char ch = 15;
int x = ch;

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Although I have a feeling you are after something more than that.

--
Mats