io - io action (extended)#

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Note

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Tip

This library has its own demo,click this link to view io demo examples

Example

-- io module is native to lua, luatOS adds some API
-- please use with OS module

-- read-only mode, opening files
local fd = io.open("/xxx.txt", "rb")
-- Read-write default, open file
local fd = io.open("/xxx.txt", "wb")
-- Write to file and truncate to 0 bytes
local fd = io.open("/xxx.txt", "wb+")
-- Append mode
local fd = io.open("/xxx.txt", "a")

-- If the file is opened successfully, fd is not nil, otherwise it is a failure.
-- Note that the files added during the refresh are all in the/luadb directory and read-only
if fd then
  -- Read the specified number of bytes, and if the data is insufficient, only the actual length of the data is returned.
  local data = fd:read(12)
  -- Read by row
  local line = fd:read("*l")
  -- Read All
  local line = fd:read("*a")

  -- data writing, only w or a mode can be called
  -- The data needs to be a string. Lua's string has a length and can contain any binary data.
  fd:write("xxxx") 
  -- The following is written 0x12, 0x13
  fd:write(string.char(0x12, 0x13))

  -- move handle, absolute coordinates
  fd:seek(1024, io.SEEK_SET)
  -- Move handle, relative coordinates
  fd:seek(1024, io.SEEK_CUR)
  -- Move the handle, reverse the absolute coordinates, from the end of the file to the head of the file.
  fd:seek(124, io.SEEK_END)

  -- After performing the operation, be sure to close the file.
  fd:close()
end

io.exists(path)#

Determine whether the file exists

Parameters

Incoming Value Type

Explanation

string

File Path

Return Value

return value type

explanation

bool

Existence returns true, otherwise false

Examples

log.info("io", "file exists", io.exists("/boottime"))

io.fileSize(path)#

Get File Size

Parameters

Incoming Value Type

Explanation

string

File Path

Return Value

return value type

explanation

int

File data, if the file does not exist will be returned nil

Examples

local fsize = io.fileSize("/bootime")
if fsize and fsize > 1024 then
  log.info("io", "file size", fsize)
end

io.readFile(path, mode, offset, len)#

Read the entire file, note the memory consumption

Parameters

Incoming Value Type

Explanation

string

File Path

string

Read mode, default “rb”

int

starting position, default 0

int

Read length, default entire file

Return Value

return value type

explanation

string

File data, if the file does not exist will be returned nil

Examples

local data = io.readFile("/bootime")
-- Note: The offset and len parameters were added in 2023.6.6
-- Read abc.txt, skip 128 bytes first, then read 512 bytes of data
local data = io.readFile("/abc.txt", "rb", 128, 512)

io.writeFile(path, data)#

Write data to a file

Parameters

Incoming Value Type

Explanation

string

File Path

string

Data

Return Value

return value type

explanation

boolean

Returns true on success, otherwise false

Examples

io.writeFile("/bootime", "1")

io.fill(buff, offset, len)#

Read the file and fill it into the zbuff, but do not move the pointer position

Parameters

Incoming Value Type

Explanation

userdata

zbuff Entity

int

The location to write to, the default is 0

int

The written length, which is minus the len of zbuff by default.offset

Return Value

return value type

explanation

boolean

Returns true on success, otherwise false

int

Returns the length actually read. If it is less than 0, the read failed.

Examples

local buff = zbuff.create(1024)
local f = io.open("/sd/test.txt")
if f then
  f:fill(buff)
end

io.mkfs(path)#

To format a file system, you must specify a mount point.

Parameters

Incoming Value Type

Explanation

string

Mount Point

Return Value

return value type

explanation

bool

Success or not

int

underlying return value

Examples

local ret, errio = io.mkfs("/sd")
log.info("fs", "mkfs", ret, errio)

io.mkdir(path)#

Create Folder

Parameters

Incoming Value Type

Explanation

string

The directory path that needs to be created

Return Value

return value type

explanation

bool

Success or not

int

underlying return value

Examples

local ret, errio = io.mkdir("/data/")
log.info("fs", "mkdir", ret, errio)

io.rmdir(path)#

Delete Folder

Parameters

Incoming Value Type

Explanation

string

Directory path to remove

Return Value

return value type

explanation

bool

Success or not

int

underlying return value

Examples

local ret, errio = io.rmdir("/data/")
log.info("fs", "rmdir", ret, errio)

io.lsdir(path, len, offset)#

List files in a directory

Parameters

Incoming Value Type

Explanation

string

The directory path that needs to be enumerated

int

Maximum length, default 10, maximum 50

int

Offset, default 0, used for paging queries when there are many directory files.

Return Value

return value type

explanation

bool

Success or not

int

underlying return value

Examples

local ret, data = io.lsdir("/data/", 10, 0)
if ret then
  log.info("fs", "lsdir", json.encode(data))
else
  log.info("fs", "lsdir", "fail", ret, data)
end

io.lsmount()#

List all mount points

Parameters

None

Return Value

return value type

explanation

table

Mount point list

Examples

local data = io.lsmount()
log.info("fs", "lsmount", json.encode(data))