OpenEuphoria

1. file check

• Posted by canadiancoder Aug 03, 2008
• 850 views

Does anyone know a simple way to check if a file already exists in euphoria? I am working on a project where, when the user saves data, I want the program to at least alert the user that an existing file of the same name will be overwritten if they use a particular file name.

Thanks, Asa.

3. Re: file check

• Posted by canadiancoder Aug 03, 2008
• 847 views

Thanks for the quick reply. It looked daunting at first but now I look at it again, I see it wouldn't be hard to iterate through the returned sequence and match a string. That's what makes Euphoria such a pleasure to use. I shudder at the thought of writing my current game project in C using the STL etc. :)

5. Re: file check

• Posted by jeremy (admin) Aug 03, 2008
• 852 views
• Last edited Aug 04, 2008

I benchmarked three different methods of checking the existence of a file:

function file_exists_dir(sequence filename) 
	return sequence(dir(filename)) 
end function 
 
function file_exists_open(sequence filename) 
	integer a = open(filename, "r") 
	if a = -1 then 
		return 0 
	end if 
	close(a) 
	return 1 
end function 
 
constant lib = open_dll("kernel32.dll"), filea = "parser.e", fileb="no.txt" 
constant f_access = define_c_func(lib, "GetFileAttributesA", {C_POINTER}, C_INT) 
function file_exists_win(sequence filename) 
	atom pFilename = allocate_string(filename) 
	integer r = c_func(f_access, {pFilename}) 
	free(pFilename) 
	return r > 0 
end function 

file_exists_dir() and file_exists_open() were about the same. file_exists_win() was much faster.

With 2376 files (C:\Windows\System32):

Time dir : 0.000129 per 
Time open: 0.000126 per 
Time win : 0.000033 per 

With 1 file (mocked directory)

Time dir : 0.000044 per 
Time open: 0.000034 per 
Time win : 0.000028 per 

The test looked for one file that did exist and one file that did not. This is a common enough operation that I will make a function called file_exists and place it in std/filesys.e for 4.0. On Unix we will use the C function access(). On DOS, it will revert to the dir() or open() method.

Jeremy

7. Re: file check

• Posted by CChris Aug 04, 2008
• 826 views

function file_exists_dir(sequence filename) 
	return sequence(dir(filename)) 
end function 
 
function file_exists_open(sequence filename) 
	integer a = open(filename, "r") 
	if a = -1 then 
		return 0 
	end if 
	close(a) 
	return 1 
end function 
 
constant lib = open_dll("kernel32.dll"), filea = "parser.e", fileb="no.txt" 
constant f_access = define_c_func(lib, "GetFileAttributesA", {C_POINTER}, C_INT) 
function file_exists_win(sequence filename) 
	atom pFilename = allocate_string(filename) 
	integer r = c_func(f_access, {pFilename}) 
	free(pFilename) 
	return r > 0 
end function 

Time dir : 0.000129 per 
Time open: 0.000126 per 
Time win : 0.000033 per 

Time dir : 0.000044 per 
Time open: 0.000034 per 
Time win : 0.000028 per 

DOS 5.0+ I believe has an int #21 call to see if a file exists, it may be jyst as fast. Look for high numbers (between #60 and #6F). I may be able to check later.

CChris