Ruby learning files and databases (1)

Input and Output:

Standard input:

A = gets, gets is to get a row of data from the standard input, lines = readlines get multiple lines of content at a time until EOF (CTRL + D)

Puts a, puts is printed to the standard output

 

File input and output:

File class to open files, can be plain text and binary files

File. Open ("text.txt"). Each {| Line | puts line}, file. Open accepts the code block. When the code block ends, the file is automatically closed.

You can also file. New ("text.txt", "R"). Each {| Line | puts line}, file. New returns the file object, and file. Close must be used to close the file.

class MyFile  attr_reader :handle  def initialize(filename)    @handle = File.new(filename,"r")  end    def finished    @handle.close  end  endf = MyFile.new("D://rb//text.txt")puts f.handle.each{|txt| puts txt}f.finished

The default each identifier is "\ n", which is defined as "and ".

Use the each_byte method to read the I/O Stream in a verbatim manner. Use the CHR method to convert to character ~

 

In addition, use the gets method to read data.

  def self.readf    File.open("D://rb//text.txt") do |f|      10.times{ puts f.gets}    end  end

At the same time, it is acceptable that the delimiter F. Gets (',') and F. GETC is the non-iterative version of each_byte.

 

Whole row read

  def self.readl    puts File.open("D://rb//text.txt").readlines.join("--")  end

Read arbitrary bytes

  def self.readb    File.open("D://rb//text.txt") do |f|      puts f.read(6)    end  end

Recommended Methods ~

File. Read (filename) and file. readlines (filename)

 

Input:

File.open("text.txt","w") do |f|f.puts("this is a test")end

File. New File Mode

File Mode	Operation
R	Read-only, starting with a file pointer
R +	Readable and writable, starts with a file pointer, and rewrites
W	Write and rewrite
W +	Readable and writable, creating new files
A	Write (additional mode)
A +	End of the readable and writable (additional mode) file pointer

Gets --> puts

GETC --> putc

Read --> write

Renamed: file. Rename ("file1", "file2 ")

Delete: file. Delete ("file1", "file2 ".....)

The comparison is the same: file. identical? ("File1", "file2 ")

Organization File Path strength: file.join('full', 'path', 'here', 'filename.txt ')

Last File Modified: file. mtime ("file1 ")

Whether the file exists: file. exist ("file1 ")

File Size: file. Size ("file1 ")

End of the file: f. EOF

Location of zhizhenjiang: Seek Method
Seek three modes

IO: seek_cur	Move n Bytes forward from current position
IO: seek_end	Move to a certain position at the end of the file. This indicates that the search starts from the end and may use a negative number.
IO: seek_set	Move to the absolute position of the file. Exactly the same as Pos =

  def self.filepoint    f = File.new("D://rb//text.txt","r+")    f.seek(-5,IO::SEEK_END)    f.putc "X"    f.close  end

 

Directory processing: (File: separator is a slash)

Display current directory: Dir. pwd

Move the current directory: Dir. chdir ("/usr/bin ")

Obtain the directory file list: Dir. Entries ("/usr/bin"). Join (''). An array is returned. The same applies to Dir. foreach. Dir ["/usr/bin/*"]

Create directory: Dir. mkdir ("dir ")

Delete Directory: Dir. Delete ("dir ")