Difference between revisions of "Io.open"

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(Created page with "__NOTOC__ '''Available since:''' Gideros 2011.6<br/> === Description === This function opens a file, in the mode specified in the string mode. It returns a new file handle, or...")
 
m (Text replacement - "</source>" to "</syntaxhighlight>")
 
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__NOTOC__
 
__NOTOC__
 
'''Available since:''' Gideros 2011.6<br/>
 
'''Available since:''' Gideros 2011.6<br/>
 +
'''Class:''' [[io]]<br/>
 +
 
=== Description ===
 
=== Description ===
This function opens a file, in the mode specified in the string mode. It returns a new file handle, or, in case of errors, nil plus an error message.  
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This function opens a file in the specified mode. The function returns a new file handle, or nil plus an error message.
 +
<syntaxhighlight lang="lua">
 +
(file) = io.open(filename, mode)
 +
</syntaxhighlight>
  
  
The mode string can be any of the following:  
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The '''mode''' string can be any of the following:
 +
*"r": read mode (the default)
 +
*"w": write mode
 +
*"a": append mode
 +
*"r+": update mode, all previous data is preserved
 +
*"w+": update mode, all previous data is erased
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*"a+": append update mode, previous data is preserved, writing is only allowed at the end of file
  
"r": read mode (the default);
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The '''mode''' string can also have a ''''b'''' at the end, which is needed in some systems to open the file in binary mode.
"w": write mode;
 
"a": append mode;
 
"r+": update mode, all previous data is preserved;
 
"w+": update mode, all previous data is erased;
 
"a+": append update mode, previous data is preserved, writing is only allowed at the end of file.
 
  
The mode string can also have a 'b' at the end, which is needed in some systems to open the file in binary mode. This string is exactly what is used in the standard C function fopen.
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This string is exactly what is used in the standard C function fopen.
<source lang="lua">
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(file), = io.open(filenamemode,)
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=== Parameters ===
</source>
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'''filename''': (string) filename to open<br/>
'''filename:''' (string) filename to open ''''''<br/>
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'''mode''': (string) mode in which to open the file '''optional''' (default = "r")<br/>
'''mode:''' (string) mode in which to open the file '''optional'''<br/>
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 +
=== Return values ===
 
'''Returns''' (file) file object<br/>
 
'''Returns''' (file) file object<br/>
 +
 +
=== Example ===
 +
'''To copy a file'''
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<syntaxhighlight lang="lua">
 +
local function copy(src, dst)
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local srcf = io.open(src, "rb")
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local dstf = io.open(dst, "wb")
 +
local size = 2^13 -- good buffer size (8K)
 +
while true do
 +
local block = srcf:read(size)
 +
if not block then break end
 +
dstf:write(block)
 +
end
 +
srcf:close()
 +
dstf:close()
 +
end
 +
</syntaxhighlight>
 +
 +
{{Io}}

Latest revision as of 14:31, 13 July 2023

Available since: Gideros 2011.6
Class: io

Description

This function opens a file in the specified mode. The function returns a new file handle, or nil plus an error message.

(file) = io.open(filename, mode)


The mode string can be any of the following:

  • "r": read mode (the default)
  • "w": write mode
  • "a": append mode
  • "r+": update mode, all previous data is preserved
  • "w+": update mode, all previous data is erased
  • "a+": append update mode, previous data is preserved, writing is only allowed at the end of file

The mode string can also have a 'b' at the end, which is needed in some systems to open the file in binary mode.

This string is exactly what is used in the standard C function fopen.

Parameters

filename: (string) filename to open
mode: (string) mode in which to open the file optional (default = "r")

Return values

Returns (file) file object

Example

To copy a file

local function copy(src, dst)
	local srcf = io.open(src, "rb")
	local dstf = io.open(dst, "wb")
	local size = 2^13 -- good buffer size (8K)
	while true do
		local block = srcf:read(size)
		if not block then break end
		dstf:write(block)
	end
	srcf:close()
	dstf:close()
end