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 once for each entry in the named directory, passing the filename of each entry as a parameter to the block.
If no block is given, an enumerator is returned instead.
Dir.foreach("testdir") {|x| puts "Got #{x}" }
produces:
Got . Got .. Got config.h Got main.rb
Returns an array containing all of the filenames except for “.” and “..” in the given directory. Will raise a SystemCallError if the named directory doesn’t exist.
The optional encoding keyword argument specifies the encoding of the directory. If not specified, the filesystem encoding is used.
Dir.children("testdir") #=> ["config.h", "main.rb"]
Calls the block once for each entry in this directory, passing the filename of each entry as a parameter to the block.
If no block is given, an enumerator is returned instead.
d = Dir.new("testdir") d.each {|x| puts "Got #{x}" }
produces:
Got . Got .. Got config.h Got main.rb
Returns an array containing all of the filenames except for “.” and “..” in this directory.
d = Dir.new("testdir") d.children #=> ["config.h", "main.rb"]
Changes the current working directory of the process to the given string. When called without an argument, changes the directory to the value of the environment variable HOME, or LOGDIR. SystemCallError (probably Errno::ENOENT) if the target directory does not exist.
If a block is given, it is passed the name of the new current directory, and the block is executed with that as the current directory. The original working directory is restored when the block exits. The return value of chdir is the value of the block. chdir blocks can be nested, but in a multi-threaded program an error will be 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).
Dir.chdir("/var/spool/mail") puts Dir.pwd Dir.chdir("/tmp") do puts Dir.pwd Dir.chdir("/usr") do puts Dir.pwd end puts Dir.pwd end puts Dir.pwd
produces:
/var/spool/mail /tmp /usr /tmp /var/spool/mail
Changes this process’s idea of the file system root. Only a privileged process may make this call. Not available on all platforms. On Unix systems, see chroot(2) for more information.
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("/dev/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
Returns the last access time (a Time object) for file, or epoch if file has not been accessed.
File.new("testfile").atime #=> Wed Dec 31 18:00:00 CST 1969
Changes permission bits on file to the bit pattern represented by mode_int. Actual effects are platform dependent; on Unix systems, see chmod(2) for details. Follows symbolic links. Also see File#lchmod.
f = File.new("out", "w"); f.chmod(0644) #=> 0