File Access

Opening files

myFile = File.new(filename, mode)
myFile = File.open(filename, mode)

File.open (filename, mode) do |myFile|
  ...
end

mode: [r, r+, w, w+, a, a+][b]   (default: r)
    r    read-only  (default)
    r+   read-write
    w    write-only (existing file erased)
    w+   read-write (existing file erased)
    a    write-only (starts at end of existing file)
    a+   read-write (starts at end of existing file)
    b    binary mode (for portability to DOS/Windows)

Reading files

# Read the next line
myFile.gets

# Read each character
myFile.each_byte do |ch|
  ...
end

# Read each line
myFile.each_line do |line|
  ...
end

# Read each line
IO.foreach("filename") do |line|
  ...
end

# Read the entire file into an array
myArray = IO.readlines("filename")

Writing files

myFile.puts expr     # Adds a newline
myFile.print expr    # Does not add a newline

File position

integer = fileobject.pos
integer = fileobject.tell   # Synonym for pos

• Gets the current file position, in bytes (0-based)
  

fileobject.rewind

• Move the file position to the beginning of the file
  

fileobject.seek(offset, relative_to)

relative_to: [IO::SEEK_SET, IO::SEEK_CUR, IO::SEEK_END]   (default: IO::SEEK_SET)
    IO::SEEK_SET    Beginning of the file
    IO::SEEK_CUR    Current file position
    IO::SEEK_END    End of the file

• Changes the file position

Closing files

myFile.close