Class: File

Inherits:
Object
  • Object
show all
Defined in:
lib/ptools.rb

Constant Summary collapse

PTOOLS_VERSION =

The version of the ptools library.

'1.2.1'
MSWINDOWS = 
false
WIN32EXTS = 
'.{exe,com,bat}'
IMAGE_EXT = 
%w/.bmp .gif .jpg .jpeg .png/

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.binary?(file) ⇒ Boolean

Returns whether or not file is a binary file. Note that this is not guaranteed to be 100% accurate. It performs a “best guess” based on a simple test of the first File.blksize characters.

Example:

File.binary?('somefile.exe') # => true
File.binary?('somefile.txt') # => false

– Based on code originally provided by Ryan Davis (which, in turn, is based on Perl’s -B switch).

Returns:

  • (Boolean) 


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# File 'lib/ptools.rb', line 93

def self.binary?(file)
  s = (File.read(file, File.stat(file).blksize) || "").split(//)
  ((s.size - s.grep(" ".."~").size) / s.size.to_f) > 0.30
end

.head(filename, num_lines = 10) ⇒ Object

In block form, yields the first num_lines from filename. In non-block form, returns an Array of num_lines

Examples:

# Return an array
File.head('somefile.txt') # => ['This is line1', 'This is line2', ...]

# Use a block
File.head('somefile.txt'){ |line| puts line }



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# File 'lib/ptools.rb', line 216

def self.head(filename, num_lines=10)
  a = []

  IO.foreach(filename){ |line|
    break if num_lines <= 0
    num_lines -= 1
    if block_given?
      yield line
    else
      a << line
    end
  }

  return a.empty? ? nil : a # Return nil in block form
end

.image?(file) ⇒ Boolean

Returns whether or not the file is an image. Only JPEG, PNG, BMP and GIF are checked against.

This method does some simple read and extension checks. For a version that is more robust, but which depends on a 3rd party C library (and is difficult to build on MS Windows), see the ‘filemagic’ library, available on the RAA.

Examples:

File.image?('somefile.jpg') # => true
File.image?('somefile.txt') # => true

– The approach I used here is based on information found at en.wikipedia.org/wiki/Magic_number_(programming)

Returns:

  • (Boolean) 


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# File 'lib/ptools.rb', line 45

def self.image?(file)
  bool = IMAGE_EXT.include?(File.extname(file).downcase)      # Match ext
  bool = bmp?(file) || jpg?(file) || png?(file) || gif?(file) # Check data
  bool
end

.middle(filename, from = 10, to = 20) ⇒ Object

In block form, yields line from up to line to. In non-block form returns an Array of lines from from to to.



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# File 'lib/ptools.rb', line 235

def self.middle(filename, from=10, to=20)
  if block_given?
    IO.readlines(filename)[from-1..to-1].each{ |line| yield line }
  else
    IO.readlines(filename)[from-1..to-1]
  end
end

.nl_convert(old_file, new_file = old_file, platform = 'dos') ⇒ Object

Converts a text file from one OS platform format to another, ala ‘dos2unix’. The possible values for platform include:

  • MS Windows -> dos, windows, win32, mswin

  • Unix/BSD -> unix, linux, bsd

  • Mac -> mac, macintosh, apple, osx

Note that this method is only valid for an ftype of “file”. Otherwise a TypeError will be raised. If an invalid format value is received, an ArgumentError is raised.



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# File 'lib/ptools.rb', line 275

def self.nl_convert(old_file, new_file = old_file, platform = 'dos')
  unless File.file?(old_file)
    raise ArgumentError, 'Only valid for plain text files'
  end

  if platform =~ /dos|windows|win32|mswin|cygwin|mingw/i
    format = "\cM\cJ"
  elsif platform =~ /unix|linux|bsd/i
    format = "\cJ"
  elsif platform =~ /mac|apple|macintosh|osx/i
    format = "\cM"
  else
    raise ArgumentError, "Invalid platform string"
  end

  orig = $\
  $\ = format

  if old_file == new_file
    require 'fileutils'
    require 'tempfile'

    begin
      temp_name = Time.new.strftime("%Y%m%d%H%M%S")
      tf = Tempfile.new('ruby_temp_' + temp_name)
      tf.open

      IO.foreach(old_file){ |line|
        line.chomp!
        tf.print line
      }
    ensure
      tf.close if tf && !tf.closed?
    end

    File.delete(old_file)
    FileUtils.cp(tf.path, old_file)
  else
    begin
      nf = File.new(new_file, 'w')
      IO.foreach(old_file){ |line|
        line.chomp!
        nf.print line
      }
    ensure
      nf.close if nf && !nf.closed?
    end
  end

  $\ = orig
  self
end

.null ⇒ Object Also known as: null_device

Returns the name of the null device (aka bitbucket) on your platform.

Examples:

# On Linux
File.null # => '/dev/null'

# On MS Windows
File.null # => 'NUL'

– The values I used here are based on information from en.wikipedia.org/wiki//dev/null



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# File 'lib/ptools.rb', line 64

def self.null
  case Config::CONFIG['host_os']
    when /mswin|win32|msdos|cygwin|mingw|windows/i
      'NUL'
    when /amiga/i
      'NIL:'
    when /openvms/i
      'NL:'
    else
      '/dev/null'
  end
end

.tail(filename, num_lines = 10) ⇒ Object

In block form, yields the last num_lines of file filename. In non-block form, it returns the lines as an array.

Note that this method slurps the entire file, so I don’t recommend it for very large files. Also note that ‘tail -f’ functionality is not present. See the ‘file-tail’ library for that.

Example:

File.tail('somefile.txt') # => ['This is line7', 'This is line8', ...]



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# File 'lib/ptools.rb', line 254

def self.tail(filename, num_lines=10)
  if block_given?
    IO.readlines(filename).reverse[0..num_lines-1].reverse.each{ |line|
      yield line
    }
  else
    IO.readlines(filename).reverse[0..num_lines-1].reverse
  end
end

.touch(filename) ⇒ Object

Changes the access and modification time if present, or creates a 0 byte file filename if it doesn’t already exist.



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# File 'lib/ptools.rb', line 331

def self.touch(filename)
  if File.exists?(filename)
    time = Time.now
    File.utime(time, time, filename)
  else
    File.open(filename, 'w'){}
  end
  self
end

.wc(filename, option = 'all') ⇒ Object

With no arguments, returns a four element array consisting of the number of bytes, characters, words and lines in filename, respectively.

Valid options are ‘bytes’, ‘characters’ (or just ‘chars’), ‘words’ and ‘lines’.



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# File 'lib/ptools.rb', line 347

def self.wc(filename, option='all')
  option.downcase!
  valid = %w/all bytes characters chars lines words/

  unless valid.include?(option)
    raise ArgumentError, "Invalid option: '#{option}'"
  end

  n = 0

  if option == 'lines'
    IO.foreach(filename){ n += 1 }
    return n
  elsif option == 'bytes'
    File.open(filename){ |f|
      f.each_byte{ n += 1 }
    }
    return n
  elsif option == 'characters' || option == 'chars'
    File.open(filename){ |f|
      while f.getc
        n += 1
      end
    }
    return n
  elsif option == 'words'
    IO.foreach(filename){ |line|
      n += line.split.length
    }
    return n
  else
    bytes,chars,lines,words = 0,0,0,0
    IO.foreach(filename){ |line|
      lines += 1
      words += line.split.length
      chars += line.split('').length
    }
    File.open(filename){ |f|
      while f.getc
        bytes += 1
      end
    }
    return [bytes,chars,words,lines]
  end
end

.whereis(program, path = ENV['PATH']) ⇒ Object

Returns an array of each program within path, or nil if it cannot be found.

On Windows, it looks for executables ending with the suffixes defined in your PATHEXT environment variable, or ‘.exe’, ‘.bat’ and ‘.com’ if that isn’t defined, which you may optionally include in program.

Examples:

File.whereis('ruby') # => ['/usr/bin/ruby', '/usr/local/bin/ruby']
File.whereis('foo')  # => nil



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# File 'lib/ptools.rb', line 163

def self.whereis(program, path=ENV['PATH'])
  if path.nil? || path.empty?
    raise ArgumentError, "path cannot be empty"
  end

  paths = []

  # Bail out early if an absolute path is provided.
  if program =~ /^\/|^[a-z]:[\\\/]/i
    program += WIN32EXTS if MSWINDOWS && File.extname(program).empty?
    found = Dir[program]
    if found[0] && File.executable?(found[0]) && !File.directory?(found[0])
      return found
    else
      return nil
    end
  end

  # Iterate over each path glob the dir + program.
  path.split(File::PATH_SEPARATOR).each{ |dir|
    next unless File.exists?(dir) # In case of bogus second argument
    file = File.join(dir, program)

    # Dir[] doesn't handle backslashes properly, so convert them. Also, if
    # the program name doesn't have an extension, try them all.
    if MSWINDOWS
      file = file.tr("\\", "/")
      file += WIN32EXTS if File.extname(program).empty?
    end

    found = Dir[file].first

    # Convert all forward slashes to backslashes if supported
    if found && File.executable?(found) && !File.directory?(found)
      found.tr!(File::SEPARATOR, File::ALT_SEPARATOR) if File::ALT_SEPARATOR
      paths << found
    end
  }

  paths.empty? ? nil : paths.uniq
end

.which(program, path = ENV['PATH']) ⇒ Object

Looks for the first occurrence of program within path.

On Windows, it looks for executables ending with the suffixes defined in your PATHEXT environment variable, or ‘.exe’, ‘.bat’ and ‘.com’ if that isn’t defined, which you may optionally include in program.

Returns nil if not found.

Examples:

File.which('ruby') # => '/usr/local/bin/ruby'
File.which('foo')  # => nil



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# File 'lib/ptools.rb', line 111

def self.which(program, path=ENV['PATH'])
  if path.nil? || path.empty?
    raise ArgumentError, "path cannot be empty"
  end

  # Bail out early if an absolute path is provided.
  if program =~ /^\/|^[a-z]:[\\\/]/i
    program += WIN32EXTS if MSWINDOWS && File.extname(program).empty?
    found = Dir[program].first
    if found && File.executable?(found) && !File.directory?(found)
      return found
    else
      return nil
    end
  end

  # Iterate over each path glob the dir + program.
  path.split(File::PATH_SEPARATOR).each{ |dir|
    next unless File.exists?(dir) # In case of bogus second argument
    file = File.join(dir, program)

    # Dir[] doesn't handle backslashes properly, so convert them. Also, if
    # the program name doesn't have an extension, try them all.
    if MSWINDOWS
      file = file.tr("\\", "/")
      file += WIN32EXTS if File.extname(program).empty?
    end

    found = Dir[file].first

    # Convert all forward slashes to backslashes if supported
    if found && File.executable?(found) && !File.directory?(found)
      found.tr!(File::SEPARATOR, File::ALT_SEPARATOR) if File::ALT_SEPARATOR
      return found
    end
  }

  nil
end

Instance Method Details

#sparse?(file) ⇒ Boolean

Returns whether or not file is a sparse file.

A sparse file is a any file where its size is greater than the number of 512k blocks it consumes, i.e. its apparent and actual file size is not the same.

See en.wikipedia.org/wiki/Sparse_file for more information.

Returns:

  • (Boolean) 


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# File 'lib/ptools.rb', line 404

def sparse?(file)
  stats = File.stat(file)
  stats.size > stats.blocks * 512
end