Difference between revisions of "Io.open"
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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 | + | 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: | ||
| + | *"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. | |
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=== Parameters === | === Parameters === | ||
| − | '''filename''': (string) filename to open <br/> | + | '''filename''': (string) filename to open<br/> |
| − | '''mode''': (string) mode in which to open the file '''optional'''<br/> | + | '''mode''': (string) mode in which to open the file '''optional''' (default = "r")<br/> |
| + | |||
=== Return values === | === Return values === | ||
'''Returns''' (file) file object<br/> | '''Returns''' (file) file object<br/> | ||
| + | |||
| + | === Example === | ||
| + | '''To copy a file''' | ||
| + | <syntaxhighlight lang="lua"> | ||
| + | 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 | ||
| + | </syntaxhighlight> | ||
| + | |||
| + | {{Io}} | ||
Latest revision as of 05:28, 30 July 2025
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
