deleting empty lines from a file

[smoking81]

hello everybody!
I am experiencing troubles with a simple program which should delete all the empty lines from a given file.
Here is my code:

#include <stdio.h>
#include <ctype.h>
#define BUFFSIZE 1024

void filecopy(FILE *from, FILE *to);

int main ()
{
	FILE *f;
	char buffer[BUFFSIZE]={0};
	if (f=fopen("changeme.txt","r+"))
	{	
		char c; int i=0,isempty=1;
		FILE *tmp;
		if (tmp=tmpfile())
		{
			while ((c=getc(f))!=EOF)
			{
				
				buffer[i++]=c;
				if (c!=' '&&c!='\n'&&c!='\t')
				{	
					isempty=0;
				}
				else
				{
					if (c=='\n'&&isempty==1)
					{
						buffer[i]='\0';
						i=0;
						line=0;
						isempty=1;
					}
					else
						if (c=='\n'&& isempty==0)
						{	
							buffer[i]='\0';
							fprintf(tmp,"%s",buffer);
							i=0;
							isempty=1;
						}
				}
				
			
			}
                        filecopy(tmp,f);
                        fclose(tmp);
		}
                else
                {
                        printf("Unable to create tmp file\n");
                 }

		
		fclose(f);
		

	}
	else 
	{
		printf("Unable to open file\n");
	}

}


void filecopy(FILE *from, FILE *to)
{
	int c;
	rewind(from);
	rewind(to);
	while ((c=getc(from))!=EOF)
	{	
		putc(c,to);
	}
	while(!feof(to))
	{
		fprintf(to," ");
	}

}

the problem is that file 'tmp' is smaller than 'f' so there is a kind of garbage left in 'f' after calling filecopy().. Of course I understand why this happens.. My problem is just that i cannot find a solution to this.. How could I truncate the rest of f after the copy?
Are there other better ways to solve this exercise?

thanks so much for your kind hints! bye

[Brad0407]

If you're making a temp copy of the new file anyways, why not just close the file and reopen it for writing "w". That will erase everything.

[smoking81]

If you're making a temp copy of the new file anyways, why not just close the file and reopen it for writing "w". That will erase everything.

i solved it in such way!
Thanks a lot!

#include <stdio.h>
#include <ctype.h>
#define BUFFSIZE 1024

void filecopy(FILE *from, FILE *to);

int main ()
{
	FILE *f;
	char buffer[BUFFSIZE]={0};
	if (f=fopen("xfile3.txt","r+"))
	{	
		char c; int i=0,isempty=1;
		FILE *tmp;
		if (tmp=tmpfile())
		{
			while ((c=getc(f))!=EOF)
			{
				buffer[i++]=c;
				if (c!=' '&&c!='\n'&&c!='\t')
				{	
					isempty=0;
				}
				else
				{
					if (c=='\n'&&isempty==1)
					{
						buffer[i]='\0';
						i=0;
						isempty=1;
					}
					else
						if (c=='\n'&& isempty==0)
						{	
							buffer[i]='\0';
							fprintf(tmp,"%s",buffer);
							i=0;
							isempty=1;
						}
				}
				
			
			}

			//LAST LINE
			if (!isempty)
			{
				buffer[i]='\0';
				fprintf(tmp,"%s",buffer);
			}
	
		        fclose (f);
	
			if (f=fopen("xfile3.txt","w+"))
			{
				filecopy(tmp,f);
				fclose(tmp);
				fclose(f);
			}
			else	
			{
				printf("Unable to reopen file f.\n");
				fclose(tmp);
			}
		}
		else
		{
			printf("Unable to create temp file.\n");
			fclose(f);
		}
		
	}
	else 
	{
		printf("Unable to open file\n");
	}

}

void filecopy(FILE *from, FILE *to)
{
	int c;
	rewind(from);
	rewind(to);
	while ((c=getc(from))!=EOF)
	{	
		putc(c,to);
	}
}

[vart]

c=getc(f)

c should be declared as int in main as well

[smoking81]

c=getc(f)

c should be declared as int in main as well

yes it's true i forgot it! thx!