The Lua I/O library is used to read and process files. It is divided into simple mode (like C) and full mode.
The simple mode (simple model) has a current input file and a current outputfile, and provides operations related to these files.
Full mode (complete model) is implemented using external file handles. It defines all file operations as file handles in the form of facing objects.
Simple mode is more appropriate when doing some simple file operations. However, when doing some advanced file operations, the simple mode seems inadequate. For example, for operations such as reading multiple files at the same time, full mode is more appropriate.
The operation statement to open the file is as follows:
file = io.open (filename [, mode]) The mode values are:
Pattern | Description |
|---|---|
| Open the file as read-only. The file must exist. |
| Open a write-only file, and if the file exists, the length of the file is cleared to 0, that is, the contents of the file will disappear. Create a file if it does not exist. |
| Open the write-only file as an attachment. If the file does not exist, the file is created, and if the file exists, the written data is added to the end of the file, that is, the original contents of the file are retained. (EOF character reserved) |
| Open the file in a read-write manner. The file must exist. |
| Open a read-write file, and if the file exists, the length of the file is cleared to zero, that is, the contents of the file will disappear. Create a file if it does not exist. |
| Similar to a, but this file is readable and writable |
| Binary mode, if the file is binary, you can add b |
| Number indicates that the file can be read or written. |
4.26.1. Simple mode #
The simple mode uses the standard I/O or uses a current input file anda current output file.
The following is Execute the above code, and you will find that the output In the above example, we used the Pattern Description Read a number and return it. Example: Reads the entire file from the current location. Example: Read the next line and return nil at the end of the file (EOF). Example: Returns a string with a specified number of characters, or nil on EOF. Example: Others file.lua file code, the file for the operation is test.lua (if you don’t need to create the file), the code is as follows:Example #
-- Open file as read-only file = io.open("test.lua", "r") -- Set the default input file to test.lua io.input(file) -- Output file first line print(io.read()) -- Close Open Files io.close(file) -- Open write only files as attachments file = io.open("test.lua", "a") -- Set the default output file to test.lua io.output(file) -- Add Lua comments on the last line of the file io.write("-- test.lua Comment at the end of the file") -- Close Open Files io.close(file)
test.lua the first line of information in the file, and added to the last line of the file lua the comments of. For example, the output from my side is:-- test.lua file
io."x" method, where io.read() we do not have a parameter, which can be one of the following tables: *n file.read("*n") *a file.read("*a") *l (default) file.read("*l") number file.read(5) io the methods are: io.tmpfile() returns a temporary file handle that opens in update mode and is automatically deleted at the end of the program io.type(file) detection obj whether it is an available file handle io.flush() write all data in the buffer to the file io.lines(optional file name) returns an iterative function, and each call will get a line in the file, and when it comes to the end of the file, it will return nil but do not close the file
4.26.2. Complete mode #
Usually we need to process multiple files at the same time. We need to use Execute the above code, and you will find that the output Other methods: Without parameters The following example uses the The output from my side is: file:function_name instead of io.function_name method. The following example shows how to process the same file at the same time:Example #
-- Open file as read-only file = io.open("test.lua", "r") -- Output file first line print(file:read()) -- Close Open Files file:close() -- Open write only files as attachments file = io.open("test.lua", "a") -- Add Lua comments on the last line of the file file:write("--test") -- Close Open Files file:close()
test.lua the first line of information in the file, and added to the last line of the file lua the comments of. For example, the output from my side is:-- test.lua file
read is consistent with the simple mode file:seek(optional whence, optional offset) set and get the current file location, return the final file location (in bytes) if you succeed, or return it if you fail nil add an error message. Parameters. `` whence``the value can be: "set" : start from the header of the file "cur" : start from the current position [default] "end" : Start at the end of the file offset : default is 0 file:seek() then return to the current position file:seek("set") navigate to the file header file:seek("end") navigate to the end of the file and return the file size file:flush() : write all data in the buffer to the file io.lines(optional file name) open the specified file filename to read the mode and return an iterative function, each call will get a line inthe file, and when it comes to the end of the file, it will return `` nil``and automatically close the file. io.lines() <=> io.input():lines() read the contents of the default input device, but do not close the file at the end, such as:for line in io.lines("main.lua") do print(line) end
seek method, navigate to the penultimatelocation of the file and use the read method of *a parameter, that is, the entire file is read from the current location (the penultimate 25th location).Example #
-- Open file as read-only file = io.open("test.lua", "r") file:seek("end",-25) print(file:read("*a")) -- Close Open Files file:close()
st.lua end of file--test