Deleting multiple files using C

**dj.turkmaster** · 01-26-2009

Hello, I am from Turkey and I'm new here

I need help with the code below:

Code:

#include <stdio.h>
#include <stdlib.h>
int main(){
	FILE *input;
	char operation[1026];
	input = fopen("av.txt", "r");
	while(!feof(input)) {
	fgets(operation, 1024, input);
	puts(operation); // Checking if fgets is working properly
	remove(operation);
	}
	fclose(input);
	return 0;
}

What I am triyng to do is reading file paths from the input file av.txt and deleting those files using the remove() funtion. But what I dont understand is that the program only deletes the last file in the av.txt. For example this is the av.txt:

c:\\3-1.exe
c:\\sile.exe
c:\\a.txt
c:\\b.txt
c:\\c.txt
c:\\e.txt
c:\\d.txt

The program only deletes c:\\d.txt. I mean it only deletes the last line. But when I check if fgets is working normal by using puts evertything seems fine. The puts function lists av.txt with no error. What is the problem? How will I delete all these files?

**Jimm0x29a** · 01-26-2009

To begin with you should check the return value from remove(3) because that will tell you why it fails. My guess is that it returns ENOENT because you have '\n' at the end of "operation".

**matsp** · 01-26-2009

I'd be willing to bet a few pennies that Jimmy is right there - and that your file doesn't have a newline on the last line.

Also, you probably don't need/want double backslashes in the file.

--
Mats

**hk_mp5kpdw** · 01-26-2009

You also don't want to use feof to control that loop. You should instead use the return value from the fgets call to control whether or not you enter the loop at all.

**dj.turkmaster** · 01-26-2009

Originally Posted by Jimm0x29a

To begin with you should check the return value from remove(3) because that will tell you why it fails. My guess is that it returns ENOENT because you have '\n' at the end of "operation".

Checking the return value from remove(3)? I am sorry but I couldn't understand what you meant my friend. Can you open it up a little?

Originally Posted by matsp

I'd be willing to bet a few pennies that Jimmy is right there - and that your file doesn't have a newline on the last line.

Also, you probably don't need/want double backslashes in the file.

--
Mats

I have tried in both ways. I put a new line at the end of the file. Also tried without a new line but it didn't work either way. Also tried with only one backslash and didin't work either. As I said before the text file is correct because it deletes the file in the last line. But unfortunantly it only deletes that file.

Originally Posted by hk_mp5kpdw

You also don't want to use feof to control that loop. You should instead use the return value from the fgets call to control whether or not you enter the loop at all.

I have checked the loop and no problem with that either. It enters the loop.

Any other advices?

**vart** · 01-26-2009

Originally Posted by dj.turkmaster

Checking the return value from remove(3)? I am sorry but I couldn't understand what you meant my friend. Can you open it up a little?

function remove returns a value right?
What it is? You do not know. You do not know if the error occured. You do not know the error code.

So check the return value of the function you call - and if it indicates failure - print out the error code

Originally Posted by dj.turkmaster

I have checked the loop and no problem with that either. It enters the loop.

Any other advices?

The problem is not enter the loop - but exit it

if the fgets fails - you still process the buffer that contains the old data

so use the return value of fgets as a loop condition, not feof

And after you call fgets - get rid of \n in the string - before passing it to remove (use the FAQ)

**matsp** · 01-26-2009

I think you managed to misunderstand EVERY SINGLE reply. In summary:
1. You should not use feof() to control the loop - you will most likely run one more loop than you actually want - so you will try to delete the last file twice. Not quite as bad as adding an extra record to a database, but still absolutely not right.

2. You are using fgets() to read lines from your file. It includes the newline at the end of the line in the data you receive. Me and jimmo suggest that you should remove the newline - that way, it will actually remove the file, rather than saying "invalid filename" or "no such file" depending on how clever it is at checking the name before trying to delete.

3. You should check the value that comes back from rename - that way, you can identify if rename actually did what you asked it, or failed for some reason - it is VERY IMPORTANT to check if something goes wrong when working with computers, so it's a good practice to get ingrained into your nerve-endings.

The (3) in "rename(3)means that in Linux, it's section three's version of rename function, so "man 3 rename", rather than some other thing called rename in another section [whatever that may be].

--
Mats

**vart** · 01-26-2009

Originally Posted by matsp

3. You should check the value that comes back from rename--

Mats

I suppose you mean remove?

**matsp** · 01-26-2009

Originally Posted by vart

I suppose you mean remove?

Of course I do -that may have just added to the confusion (there was another thread on rename recently - but I didn't even comment in that one, AFAICR...)

--
Mats

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