io - io action (extended)#
Adapted Air780E
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))