Putting content from one file into another not working

Question

Im writing a program that takes a files content and reverses it and I want to put the reversed output into an output.txt file but nothing is getting copied into the output.txt the content is reversing fine but not copying over to the other file. (I have created an "output.txt" file that I want the orignial text to be copied over to. here is my code:

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

int main(int argc, char *argv[]){

    FILE *fp, *fp2;
    char ch;
    int a;
    char c;
    int s;
    int i, pos;
    int choice = 0;

    fp = fopen(argv[1],"r");
    if (fp == NULL) 
    {
        printf("file doesnt exist \n");
    }

    fp2 = fopen(argv[2], "w");
        if(fp2 == NULL) {
            printf("ERRORRR");
            exit(1);
    }

    fseek(fp,0,SEEK_END);
    pos=ftell(fp);

    i = 0;
    while (i < pos){
        i++;
        fseek(fp,-i,SEEK_END);
        ch = fgetc(fp);

        printf("%c", ch);
        fputc(fp, fp2);
    }

    /*
    do {
        a = fgetc(fp);
        fputc(a,fp2);
    }
    while ( a != EOF);
    */

    return 0;
}

Im fairly new to c especially working with files but I do get a compiler warning @SamiKuhmonen — Alopax, Oct 23 '17 at 03:55
First of all. [`fgetc` returns an **`int`**](https://stackoverflow.com/questions/35356322/difference-between-int-and-char-in-getchar-fgetc-and-putchar-fputc). You cannot seek like this in a file that is not opened in **binary mode** (**`rb`**). The output must be opened for writing, `w`. — Antti Haapala -- Слава Україні, Oct 23 '17 at 03:55
A [mcve] needs **all the output from the compiler that you get**. — Antti Haapala -- Слава Україні, Oct 23 '17 at 03:56

C Damo · Answer 1 · 2017-10-23T03:56:39.400

1

I think you have to open the second file in "Write mode".

fp2 = fopen(argv[2], "w");

And like @Sami Kuhmonen said there's something wrong with the line fputc(fp, fp2); As fputc takes two arguments.

fputc(int character, File *stream);

edited Oct 23 '17 at 03:56

answered Oct 23 '17 at 03:53

C Damo

313
2
11

Ok I changed it to write mode but it is still not working do you see any other flaws in the program? – Alopax Oct 23 '17 at 03:56
I figured it out ! I ended up doing fputc(ch,fp2); – Alopax Oct 23 '17 at 03:59

Adam · Answer 2 · 2017-10-23T12:35:21.597

0

try this:

while (c){
     c=getc(fp1);
     fputc(c,fp2);
}

edited Oct 23 '17 at 12:35

answered Oct 23 '17 at 05:18

Adam

23
4

The `fputc()` argument order is wrong. – Armali Oct 23 '17 at 06:03

Putting content from one file into another not working

2 Answers2