Returns a simpler approximation of the value (flt-|eps| <= result <= flt+|eps|). If the optional argument eps is not given, it will be chosen automatically.
0.3.rationalize #=> (3/10) 1.333.rationalize #=> (1333/1000) 1.333.rationalize(0.01) #=> (4/3)
See also Float#to_r.
Returns the Fiber scheduler, that was last set for the current thread with Fiber.set_scheduler. Returns nil if no scheduler is set (which is the default), and non-blocking fibers’ behavior is the same as blocking. (see “Non-blocking fibers” section in class docs for details about the scheduler concept).
The method is expected to immediately run the provided block of code in a separate non-blocking fiber.
puts "Go to sleep!" Fiber.set_scheduler(MyScheduler.new) Fiber.schedule do puts "Going to sleep" sleep(1) puts "I slept well" end puts "Wakey-wakey, sleepyhead"
Assuming MyScheduler is properly implemented, this program will produce:
Go to sleep! Going to sleep Wakey-wakey, sleepyhead ...1 sec pause here... I slept well
…e.g. on the first blocking operation inside the Fiber (sleep(1)), the control is yielded to the outside code (main fiber), and at the end of that execution, the scheduler takes care of properly resuming all the blocked fibers.
Note that the behavior described above is how the method is expected to behave, actual behavior is up to the current scheduler’s implementation of Fiber::Scheduler#fiber method. Ruby doesn’t enforce this method to behave in any particular way.
If the scheduler is not set, the method raises RuntimeError (No scheduler is available!).
Calls the block with each entry name in the directory at dirpath; sets the given encoding onto each passed entry_name:
Dir.foreach('/example') {|entry_name| p entry_name }
Output:
"config.h" "lib" "main.rb" ".." "."
Encoding:
Dir.foreach('/example') {|entry_name| p entry_name.encoding; break } Dir.foreach('/example', encoding: 'US-ASCII') {|entry_name| p entry_name.encoding; break }
Output:
#<Encoding:UTF-8> #<Encoding:US-ASCII>
See String Encoding.
Returns an enumerator if no block is given.
Returns an array of the entry names in the directory at dirpath except for '.' and '..'; sets the given encoding onto each returned entry name:
Dir.children('/example') # => ["config.h", "lib", "main.rb"] Dir.children('/example').first.encoding # => #<Encoding:UTF-8> Dir.children('/example', encoding: 'US-ASCII').first.encoding # => #<Encoding:US-ASCII>
See String Encoding.
Raises an exception if the directory does not exist.
Returns the dirpath string that was used to create self (or nil if created by method Dir.for_fd):
Dir.new('example').path # => "example"
Calls the block with each entry name in self:
Dir.new('example').each {|entry_name| p entry_name }
Output:
"." ".." "config.h" "lib" "main.rb"
With no block given, returns an Enumerator.
Returns an array of the entry names in self except for '.' and '..':
dir = Dir.new('/example') dir.children # => ["config.h", "lib", "main.rb"]
Changes the current working directory to self:
Dir.pwd # => "/" dir = Dir.new('example') dir.chdir Dir.pwd # => "/example"
With a block, temporarily changes the working directory:
Calls the block.
Changes to the given directory.
Executes the block (yields no args).
Restores the previous working directory.
Returns the block’s return value.
Uses Dir.fchdir if available, and Dir.chdir if not, see those methods for caveats.
Changes the current working directory to the directory specified by the integer file descriptor fd.
When passing a file descriptor over a UNIX socket or to a child process, using fchdir instead of chdir avoids the time-of-check to time-of-use vulnerability
With no block, changes to the directory given by fd:
Dir.chdir('/var/spool/mail') Dir.pwd # => "/var/spool/mail" dir = Dir.new('/usr') fd = dir.fileno Dir.fchdir(fd) Dir.pwd # => "/usr"
With a block, temporarily changes the working directory:
Calls the block with the argument.
Changes to the given directory.
Executes the block (yields no args).
Restores the previous working directory.
Returns the block’s return value.
Example:
Dir.chdir('/var/spool/mail') Dir.pwd # => "/var/spool/mail" dir = Dir.new('/tmp') fd = dir.fileno Dir.fchdir(fd) do Dir.pwd # => "/tmp" end Dir.pwd # => "/var/spool/mail"
This method uses the fchdir() function defined by POSIX 2008; the method is not implemented on non-POSIX platforms (raises NotImplementedError).
Raises an exception if the file descriptor is not valid.
In a multi-threaded program an error is raised if a thread attempts to open a chdir block while another thread has one open, or a call to chdir without a block occurs inside a block passed to chdir (even in the same thread).
Changes the current working directory.
With argument new_dirpath and no block, changes to the given dirpath:
Dir.pwd # => "/example" Dir.chdir('..') # => 0 Dir.pwd # => "/"
With no argument and no block:
Changes to the value of environment variable HOME if defined.
Otherwise changes to the value of environment variable LOGDIR if defined.
Otherwise makes no change.
With argument new_dirpath and a block, temporarily changes the working directory:
Calls the block with the argument.
Changes to the given directory.
Executes the block (yielding the new path).
Restores the previous working directory.
Returns the block’s return value.
Example:
Dir.chdir('/var/spool/mail') Dir.pwd # => "/var/spool/mail" Dir.chdir('/tmp') do Dir.pwd # => "/tmp" end Dir.pwd # => "/var/spool/mail"
With no argument and a block, calls the block with the current working directory (string) and returns the block’s return value.
Calls to Dir.chdir with blocks may be nested:
Dir.chdir('/var/spool/mail') Dir.pwd # => "/var/spool/mail" Dir.chdir('/tmp') do Dir.pwd # => "/tmp" Dir.chdir('/usr') do Dir.pwd # => "/usr" end Dir.pwd # => "/tmp" end Dir.pwd # => "/var/spool/mail"
In a multi-threaded program an error is raised if a thread attempts to open a chdir block while another thread has one open, or a call to chdir without a block occurs inside a block passed to chdir (even in the same thread).
Raises an exception if the target directory does not exist.
Changes the root directory of the calling process to that specified in dirpath. The new root directory is used for pathnames beginning with '/'. The root directory is inherited by all children of the calling process.
Only a privileged process may call chroot.
See Linux chroot.
Returns a File::Stat object for the file at filepath (see File::Stat):
File.stat('t.txt').class # => File::Stat
Like File::stat, but does not follow the last symbolic link; instead, returns a File::Stat object for the link itself.
File.symlink('t.txt', 'symlink') File.stat('symlink').size # => 47 File.lstat('symlink').size # => 5
Returns the last access time for the named file as a Time object.
file_name can be an IO object.
File.atime("testfile") #=> Wed Apr 09 08:51:48 CDT 2003
Changes permission bits on the named file(s) to the bit pattern represented by mode_int. Actual effects are operating system dependent (see the beginning of this section). On Unix systems, see chmod(2) for details. Returns the number of files processed.
File.chmod(0644, "testfile", "out") #=> 2
Changes the owner and group of the named file(s) to the given numeric owner and group id’s. Only a process with superuser privileges may change the owner of a file. The current owner of a file may change the file’s group to any group to which the owner belongs. A nil or -1 owner or group id is ignored. Returns the number of files processed.
File.chown(nil, 100, "testfile")
Equivalent to File::chmod, but does not follow symbolic links (so it will change the permissions associated with the link, not the file referenced by the link). Often not available.
Equivalent to File::chown, but does not follow symbolic links (so it will change the owner associated with the link, not the file referenced by the link). Often not available. Returns number of files in the argument list.
Returns the current umask value for this process. If the optional argument is given, set the umask to that value and return the previous value. Umask values are subtracted from the default permissions, so a umask of 0222 would make a file read-only for everyone.
File.umask(0006) #=> 18 File.umask #=> 6
Truncates the file file_name to be at most integer bytes long. Not available on all platforms.
f = File.new("out", "w") f.write("1234567890") #=> 10 f.close #=> nil File.truncate("out", 5) #=> 0 File.size("out") #=> 5
Returns the real (absolute) pathname of pathname in the actual filesystem not containing symlinks or useless dots.
If dir_string is given, it is used as a base directory for interpreting relative pathname instead of the current directory.
All components of the pathname must exist when this method is called.
Returns the real (absolute) pathname of pathname in the actual filesystem. The real pathname doesn’t contain symlinks or useless dots.
If dir_string is given, it is used as a base directory for interpreting relative pathname instead of the current directory.
The last component of the real pathname can be nonexistent.
Returns the string representation of the path
File.path(File::NULL) #=> "/dev/null" File.path(Pathname.new("/tmp")) #=> "/tmp"
Like File#stat, but does not follow the last symbolic link; instead, returns a File::Stat object for the link itself:
File.symlink('t.txt', 'symlink') f = File.new('symlink') f.stat.size # => 47 f.lstat.size # => 11