Thread: I can not write to a txt file using this program

I run this program like this from the command line:

Code:

./writer mytext.txt

and then the file "mytext.txt" is created and cli notifies and prompts for writing into it, then I write something like "Hello World!" and finish it by giving the specific EOF of my OS and the program ends without any errors. But when I open the text file nothing is in there. I've also "cleaned up after myself" by flushing wherever I felt it's needed. Please help.

Code:

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


int main(int argc, char **argv){
    FILE *fp;
    int ch;
    if(argc != 2){
        printf("Wrong number of arguments entered. Filename: %s",argv[1]);
        exit(EXIT_FAILURE);
    }
    fp = fopen(argv[1],"a+");
    printf("File opened successfully. Write to file now:\n");
    fflush(NULL);
    while((ch = getchar()) != EOF){
        fprintf(fp,"%c",ch);
    }
    fclose(fp);
    return 0;
}

Originally Posted by laserlight

I compiled and ran your program and it worked for me to write "Hello world!" to the file.

Ahhh... Thanks the problem then must be with this dumb mingw and windows. Honestly, it doesn't work for me. It seems that I should forget about windows if I want to learn C with less silly problems like this and switch to Linux.
Thanks for the help.

Switching to Linux is a very big step. Why don't you try clang or even Pelles IDE first ?

It seems that I should forget about windows if I want to learn C with less silly problems like this and switch to Linux.

Correct. For starters, you can also consider running your Linux distro on a Virtual Machine within Windows, or maybe even through WSL (not sure how limited it is).

I'm a little bit skeptical about Ctrl-Z, given that you say you are typing "./" in front of your program name, which a Windows shell won't recognize. Are you popping open a terminal other than the Windows command line? If so, Ctrl-Z becomes suspend (IIRC) and Ctrl-D is EOF. Also:
(1) I like that you're checking the command-line arguments; I don't like the actual error printing that you're doing. If they don't supply a filename, then argv[1] is going to be not worth printing; if there are too many arguments it will just show them one of them. I would prefer the more customary thing of showing a proper invocation in the usage statement.
(2) If you're going to print "File successfully opened" you should actually check the result of fopen to make sure that is true.

In terms of cmd disappearing: why not just open a command prompt (hit the Win key, type "cmd", and off you go) and run the command there? The program will run in that window and you'll see the output etc. I guess that depends a bit on whether you're compiling locally. I don't remember having too much trouble getting MinGW installed, but (for example) at work I have trouble keeping that in my path so I often have to start when I open a cmd window by doing set PATH=%PATH%;h:\codeblocks\mingw\bin (you can tell how I installed MinGW there, but if you don't like a GUI you can definitely install it by itself).

Yeah, Ctrl-C is just going to immediately abort; if you were flushing after every character that would (a) be very inefficient but (b) would make sure that the file was written even if you abort instead of end normally. When you say Ctrl-D is doing nothing, it's not ending your program at all? (I would expect any version of bash to send EOF on a Ctrl-D, but maybe the Windows version is weird.)

Originally Posted by tabstop

In terms of cmd disappearing: why not just open a command prompt (hit the Win key, type "cmd", and off you go) and run the command there?

Well, I'm a bit confused now, well for every practicing code I might create a different directory so...?? cmd always gets initialized in my user directory. but for example, the directory of my code is in D:\\foo\bar. Maybe I don't understand you correctly here.

Originally Posted by tabstop

When you say Ctrl-D is doing nothing, it's not ending your program at all? (I would expect any version of bash to send EOF on a Ctrl-D, but maybe the Windows version is weird.)

Yes, it's literally doing NOTHING. I think it's a git bash thing because I've had other problems with it too before. doing other stuff with it. Hopefully, "Babun" will be better. I'll post here when I tried it.

Originally Posted by narniat

Well, I'm a bit confused now, well for every practicing code I might create a different directory so...?? cmd always gets initialized in my user directory. but for example, the directory of my code is in D:\\foo\bar. Maybe I don't understand you correctly here.

There are all sorts of things you can do in a command shell, and one of them is change directories! It's even cd, just like in a *nix shell. Type cd d:\foo\bar and you're there.