6.2 KiB
file Module
The file module provides access to the file system and its individual files.
The file system is a flat file system, with no notion of directories/folders.
Only one file can be open at any given time.
file.close()
Closes the open file, if any.
Syntax
file.close()
Parameters
none
Returns
nil
Example
-- open 'init.lua', print the first line.
file.open("init.lua", "r")
print(file.readline())
file.close()
See also
file.flush()
Flushes any pending writes to the file system, ensuring no data is lost on a restart. Closing the open file using file.close() performs an implicit flush as well.
Syntax
file.flush()
Parameters
none
Returns
nil
Example
-- open 'init.lua' in 'a+' mode
file.open("init.lua", "a+")
-- write 'foo bar' to the end of the file
file.write('foo bar')
file.flush()
-- write 'baz' too
file.write('baz')
file.close()
See also
file.format()
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.
Syntax
file.format()
Parameters
none
Returns
nil
See also
file.fsinfo()
Return size information for the file system, in bytes.
Syntax
file.fsinfo()
Parameters
none
Returns
remaining(number)used(number)total(number)
Example
-- get file system info
remaining, used, total=file.fsinfo()
print("\nFile system info:\nTotal : "..total.." Bytes\nUsed : "..used.." Bytes\nRemain: "..remaining.." Bytes\n")
file.list()
Lists all files in the file system.
Syntax
file.list()
Parameters
none
Returns
a lua table which contains the {file name: file size} pairs
Example
l = file.list();
for k,v in pairs(l) do
print("name:"..k..", size:"..v)
end
file.open()
Opens a file for access, potentially creating it (for write modes).
When done with the file, it must be closed using file.close().
Syntax
file.open(filename, mode)
Parameters
filenamefile to be opened, directories are not supportedmode:- "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
Returns
nil if file not opened, or not exists (read modes). true if file opened ok.
Example
-- open 'init.lua', print the first line.
file.open("init.lua", "r")
print(file.readline())
file.close()
See also
file.read()
Read content from the open file.
Syntax
file.read([n_or_str])
Parameters
n_or_str:- if nothing passed in, read all byte in file
- if pass a number n, then read n bytes from file, or EOF is reached
- if pass a string "str", then read until 'str' or EOF is reached
Returns
fdile content in string, or nil when EOF
Example
-- print the first line of 'init.lua'
file.open("init.lua", "r")
print(file.read('\n'))
file.close()
-- print the first 5 byte of 'init.lua'
file.open("init.lua", "r")
print(file.read(5))
file.close()
See also
file.readline()
Read the next line from the open file.
Syntax
file.readline()
Parameters
none
Returns
File content in string, line by line, include EOL('\n'). Return nil when EOF.
Example
-- print the first line of 'init.lua'
file.open("init.lua", "r")
print(file.readline())
file.close()
See also
file.remove()
Remove a file from the file system. The file must not be currently open.
###Syntax
file.remove(filename)
Parameters
filename file to remove
Returns
nil
Example
-- remove "foo.lua" from file system.
file.remove("foo.lua")
See also
file.rename()
Renames a file. If a file is currently open, it will be closed first.
Syntax
file.rename(oldname, newname)
Parameters
oldnameold file namenewnamenew file name
Returns
true on success, false on error.
Example
-- rename file 'temp.lua' to 'init.lua'.
file.rename("temp.lua","init.lua")
file.seek()
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.
Syntax
file.seek([whence [, offset]])
Parameters
whence- "set": base is position 0 (beginning of the file)
- "cur": base is current position (default value)
- "end": base is end of file
offsetdefault 0
If no parameters are given, the function simply returns the current file offset.
Returns
the resulting file position, or nil on error
Example
file.open("init.lua", "r")
-- skip the first 5 bytes of the file
file.seek("set", 5)
print(file.readline())
file.close()
See also
file.write()
Write a string to the open file.
Syntax
file.write(string)
Parameters
string content to be write to file
Returns
true if the write is ok, nil on error
Example
-- open 'init.lua' in 'a+' mode
file.open("init.lua", "a+")
-- write 'foo bar' to the end of the file
file.write('foo bar')
file.close()
See also
file.writeline()
Write a string to the open file and append '\n' at the end.
Syntax
file.writeline(string)
Parameters
string content to be write to file
Returns
true if write ok, nil on error
Example
-- open 'init.lua' in 'a+' mode
file.open("init.lua", "a+")
-- write 'foo bar' to the end of the file
file.writeline('foo bar')
file.close()