379 lines
6.9 KiB
Markdown
379 lines
6.9 KiB
Markdown
# file Module
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The file module provides access to the file system and its individual files.
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The file system is a flat file system, with no notion of directories/folders.
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Only one file can be open at any given time.
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## file.close()
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Closes the open file, if any.
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#### Syntax
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`file.close()`
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#### Parameters
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none
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#### Returns
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`nil`
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#### Example
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```lua
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-- open 'init.lua', print the first line.
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file.open("init.lua", "r")
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print(file.readline())
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file.close()
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```
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#### See also
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[`file.open()`](#fileopen)
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## file.exists()
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Determines whether the specified file exists.
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#### Syntax
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`file.exists(filename)`
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#### Parameters
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- `filename` file to check
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#### Returns
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true of the file exists (even if 0 bytes in size), and false if it does not exist
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#### Example
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```lua
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files = file.list()
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if files["device.config"] then
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print("Config file exists")
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end
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if file.exists("device.config") then
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print("Config file exists")
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end
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```
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#### See also
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[`file.list()`](#filelist)
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## file.flush()
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Flushes any pending writes to the file system, ensuring no data is lost on a restart. Closing the open file using [`file.close()`](#fileclose) performs an implicit flush as well.
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#### Syntax
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`file.flush()`
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#### Parameters
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none
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#### Returns
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`nil`
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#### Example
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```lua
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-- open 'init.lua' in 'a+' mode
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file.open("init.lua", "a+")
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-- write 'foo bar' to the end of the file
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file.write('foo bar')
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file.flush()
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-- write 'baz' too
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file.write('baz')
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file.close()
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```
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#### See also
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[`file.close()`](#fileclose)
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## file.format()
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Format the file system. Completely erases any existing file system and writes a new one. Depending on the size of the flash chip in the ESP, this may take several seconds.
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#### Syntax
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`file.format()`
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#### Parameters
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none
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#### Returns
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`nil`
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#### See also
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[`file.remove()`](#fileremove)
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## file.fscfg ()
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Returns the flash address and physical size of the file system area, in bytes.
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#### Syntax
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`file.fscfg()`
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#### Parameters
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none
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#### Returns
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- `flash address` (number)
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- `size` (number)
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#### Example
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```lua
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print(string.format("0x%x", file.fscfg()))
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```
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## file.fsinfo()
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Return size information for the file system, in bytes.
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#### Syntax
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`file.fsinfo()`
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#### Parameters
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none
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#### Returns
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- `remaining` (number)
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- `used` (number)
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- `total` (number)
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#### Example
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```lua
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-- get file system info
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remaining, used, total=file.fsinfo()
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print("\nFile system info:\nTotal : "..total.." Bytes\nUsed : "..used.." Bytes\nRemain: "..remaining.." Bytes\n")
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```
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## file.list()
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Lists all files in the file system.
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#### Syntax
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`file.list()`
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#### Parameters
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none
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#### Returns
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a lua table which contains the {file name: file size} pairs
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#### Example
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```lua
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l = file.list();
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for k,v in pairs(l) do
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print("name:"..k..", size:"..v)
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end
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```
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## file.open()
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Opens a file for access, potentially creating it (for write modes).
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When done with the file, it must be closed using `file.close()`.
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#### Syntax
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`file.open(filename, mode)`
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#### Parameters
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- `filename` file to be opened, directories are not supported
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- `mode`:
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- "r": read mode (the default)
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- "w": write mode
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- "a": append mode
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- "r+": update mode, all previous data is preserved
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- "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
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#### Returns
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`nil` if file not opened, or not exists (read modes). `true` if file opened ok.
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#### Example
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```lua
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-- open 'init.lua', print the first line.
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file.open("init.lua", "r")
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print(file.readline())
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file.close()
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```
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#### See also
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- [`file.close()`](#fileclose)
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- [`file.readline()`](#filereadline)
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## file.read()
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Read content from the open file.
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#### Syntax
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`file.read([n_or_str])`
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#### Parameters
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- `n_or_str`:
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- if nothing passed in, read all byte in file
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- if pass a number n, then read n bytes from file, or EOF is reached
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- if pass a string "str", then read until 'str' or EOF is reached
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#### Returns
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fdile content in string, or nil when EOF
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#### Example
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```lua
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-- print the first line of 'init.lua'
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file.open("init.lua", "r")
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print(file.read('\n'))
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file.close()
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-- print the first 5 byte of 'init.lua'
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file.open("init.lua", "r")
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print(file.read(5))
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file.close()
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```
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#### See also
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- [`file.open()`](#fileopen)
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- [`file.readline()`](#filereadline)
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## file.readline()
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Read the next line from the open file.
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#### Syntax
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`file.readline()`
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#### Parameters
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none
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#### Returns
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File content in string, line by line, include EOL('\n'). Return `nil` when EOF.
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#### Example
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```lua
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-- print the first line of 'init.lua'
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file.open("init.lua", "r")
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print(file.readline())
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file.close()
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```
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#### See also
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- [`file.open()`](#fileopen)
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- [`file.close()`](#fileclose)
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- [`file.read()`](#filereade)
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## file.remove()
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Remove a file from the file system. The file must not be currently open.
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###Syntax
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`file.remove(filename)`
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#### Parameters
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`filename` file to remove
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#### Returns
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`nil`
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#### Example
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```lua
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-- remove "foo.lua" from file system.
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file.remove("foo.lua")
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```
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#### See also
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[`file.open()`](#fileopen)
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## file.rename()
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Renames a file. If a file is currently open, it will be closed first.
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#### Syntax
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`file.rename(oldname, newname)`
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#### Parameters
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- `oldname` old file name
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- `newname` new file name
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#### Returns
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`true` on success, `false` on error.
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#### Example
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```lua
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-- rename file 'temp.lua' to 'init.lua'.
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file.rename("temp.lua","init.lua")
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```
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## file.seek()
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Sets and gets the file position, measured from the beginning of the file, to the position given by offset plus a base specified by the string whence.
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#### Syntax
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`file.seek([whence [, offset]])`
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#### Parameters
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- `whence`
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- "set": base is position 0 (beginning of the file)
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- "cur": base is current position (default value)
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- "end": base is end of file
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- `offset` default 0
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If no parameters are given, the function simply returns the current file offset.
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#### Returns
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the resulting file position, or `nil` on error
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#### Example
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```lua
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file.open("init.lua", "r")
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-- skip the first 5 bytes of the file
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file.seek("set", 5)
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print(file.readline())
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file.close()
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```
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#### See also
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[`file.open()`](#fileopen)
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## file.write()
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Write a string to the open file.
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#### Syntax
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`file.write(string)`
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#### Parameters
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`string` content to be write to file
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#### Returns
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`true` if the write is ok, `nil` on error
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#### Example
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```lua
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-- open 'init.lua' in 'a+' mode
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file.open("init.lua", "a+")
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-- write 'foo bar' to the end of the file
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file.write('foo bar')
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file.close()
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```
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#### See also
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- [`file.open()`](#fileopen)
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- [`file.writeline()`](#filewriteline)
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## file.writeline()
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Write a string to the open file and append '\n' at the end.
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#### Syntax
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`file.writeline(string)`
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#### Parameters
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`string` content to be write to file
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#### Returns
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`true` if write ok, `nil` on error
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#### Example
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```lua
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-- open 'init.lua' in 'a+' mode
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file.open("init.lua", "a+")
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-- write 'foo bar' to the end of the file
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file.writeline('foo bar')
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file.close()
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```
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#### See also
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- [`file.open()`](#fileopen)
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- [`file.readline()`](#filereadline)
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