FileOpen: Difference between revisions

Revision as of 00:08, 14 February 2015

Opens an existing file for reading and writing.

[[{{{image}}}\|link=\|]]	Note: To prevent memory leaks, ensure each successful call to fileOpen has a matching call to fileClose

[[{{{image}}}\|link=\|]]	Tip: The file functions should not be used to implement configuration files. It is encouraged to use the XML functions for this instead.

Syntax

file fileOpen ( string filePath [, bool readOnly = false ])

OOP Syntax Help! I don't understand this!

Method: File(...)

Required Arguments

filePath: The filepath of the file in the following format: ":resourceName/path". 'resourceName' is the name of the resource the file is in, and 'path' is the path from the root directory of the resource to the file.

For example, if there is a file named 'coolObjects.txt' in the resource 'objectSearch', it can be opened from another resource this way: fileOpen(":objectSearch/coolObjects.txt").

If the file is in the current resource, only the file path is necessary, e.g. fileOpen("coolObjects.txt").

Optional Arguments

readOnly: By default, the file is opened with reading and writing access. You can specify true for this parameter if you only need reading access.

Returns

If successful, returns a file handle for the file. Otherwise returns false (f.e. if the file doesn't exist).

Example

This example opens the file test.txt that is in the root of the current resource, and outputs its contents to the console.

local hFile = fileOpen("test.txt", true)       -- attempt to open the file (read only)
if hFile then                                  -- check if it was successfully opened
    local buffer
    while not fileIsEOF(hFile) do              -- as long as we're not at the end of the file...
        buffer = fileRead(hFile, 500)          -- ... read the next 500 bytes...
        outputConsole(buffer)                  -- ... and output them to the console
    end
    fileClose(hFile)                           -- close the file once we're done with it
else
    outputConsole("Unable to open test.txt")
end

This example show how to append data to an existing file:

local hFile = fileOpen("test.txt")             -- attempt to open the file (read and write mode)
if hFile then                                  -- check if it was successfully opened
    fileSetPos( hFile, fileGetSize( hFile ) )  -- move position to the end of the file
    fileWrite(hFile, "hello" )                 -- append data
    fileClose(hFile)                           -- close the file once we're done with it
else
    outputConsole("Unable to open test.txt")
end

@@ Line 1: / Line 1: @@
 __NOTOC__
 {{Server client function}}
 Opens an existing file for reading and writing.
+{{Note|To prevent memory leaks, ensure each successful call to [[fileOpen]] has a matching call to [[fileClose]]}}
-'''Note:''' The file functions should not be used to implement configuration files. It is encouraged to use the XML functions for this instead.
+{{Tip|The file functions should not be used to implement configuration files. It is encouraged to use the XML functions for this instead.}}
 ==Syntax==
 <syntaxhighlight lang="lua">
@@ Line 39: / Line 37: @@
 </syntaxhighlight>
-Notice that you can't simply do ''buffer = fileRead("test.txt", 500)''. Instead, file functions operate on a '''file handle''', which is a special object representing an open file. fileOpen gives us such a handle.
+This example show how to append data to an existing file:
+<syntaxhighlight lang="lua">
-It is also important to remember to close a file after you've finished all your operations on it, especially if you've been writing to the file. If you don't close a file and your resource crashes, all changes to the file may be lost.
+local hFile = fileOpen("test.txt")             -- attempt to open the file (read and write mode)
+if hFile then                                  -- check if it was successfully opened
+    fileSetPos( hFile, fileGetSize( hFile ) )  -- move position to the end of the file
+    fileWrite(hFile, "hello" )                 -- append data
+    fileClose(hFile)                           -- close the file once we're done with it
+else
+    outputConsole("Unable to open test.txt")
+end
+</syntaxhighlight>
 ==See Also==
 {{File functions}}