Returns a fiber-local for the given key. If the key can’t be found, there are several options: With no other arguments, it will raise a KeyError exception; if default is given, then that will be returned; if the optional code block is specified, then that will be run and its result returned. See Thread#[] and Hash#fetch.
Calls the operating system function identified by num and returns the result of the function or raises SystemCallError if it failed.
Arguments for the function can follow num. They must be either String objects or Integer objects. A String object is passed as a pointer to the byte sequence. An Integer object is passed as an integer whose bit size is the same as a pointer. Up to nine parameters may be passed.
The function identified by num is system dependent. On some Unix systems, the numbers may be obtained from a header file called syscall.h.
syscall 4, 1, "hello\n", 6 # '4' is write(2) on our box
produces:
hello
Calling syscall on a platform which does not have any way to an arbitrary system function just fails with NotImplementedError.
Note: syscall is essentially unsafe and unportable. Feel free to shoot your foot. The DL (Fiddle) library is preferred for safer and a bit more portable programming.
Executes command… in a subshell. command… is one of following forms.
commandlinecommand line string which is passed to the standard shell
cmdname, arg1, ...command name and one or more arguments (no shell)
[cmdname, argv0], arg1, ...command name, argv[0] and zero or more arguments (no shell)
system returns true if the command gives zero exit status, false for non zero exit status. Returns nil if command execution fails. An error status is available in $?.
If the exception: true argument is passed, the method raises an exception instead of returning false or nil.
The arguments are processed in the same way as for Kernel#spawn.
The hash arguments, env and options, are same as exec and spawn. See Kernel#spawn for details.
system("echo *") system("echo", "*")
produces:
config.h main.rb *
Error handling:
system("cat nonexistent.txt") # => false system("catt nonexistent.txt") # => nil system("cat nonexistent.txt", exception: true) # RuntimeError (Command failed with exit 1: cat) system("catt nonexistent.txt", exception: true) # Errno::ENOENT (No such file or directory - catt)
See Kernel#exec for the standard shell.
Equivalent to ($_.dup).chop!, except nil is never returned. See String#chop!. Available only when -p/-n command line option specified.
Equivalent to $_ = $_.chomp(string). See String#chomp. Available only when -p/-n command line option specified.
catch executes its block. If throw is not called, the block executes normally, and catch returns the value of the last expression evaluated.
catch(1) { 123 } # => 123
If throw(tag2, val) is called, Ruby searches up its stack for a catch block whose tag has the same object_id as tag2. When found, the block stops executing and returns val (or nil if no second argument was given to throw).
catch(1) { throw(1, 456) } # => 456 catch(1) { throw(1) } # => nil
When tag is passed as the first argument, catch yields it as the parameter of the block.
catch(1) {|x| x + 2 } # => 3
When no tag is given, catch yields a new unique object (as from Object.new) as the block parameter. This object can then be used as the argument to throw, and will match the correct catch block.
catch do |obj_A| catch do |obj_B| throw(obj_B, 123) puts "This puts is not reached" end puts "This puts is displayed" 456 end # => 456 catch do |obj_A| catch do |obj_B| throw(obj_A, 123) puts "This puts is still not reached" end puts "Now this puts is also not reached" 456 end # => 123
When called with positive integer argument n and a block, calls the block with each element, then does so again, until it has done so n times; returns nil:
a = [] (1..4).cycle(3) {|element| a.push(element) } # => nil a # => [1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4] a = [] ('a'..'d').cycle(2) {|element| a.push(element) } a # => ["a", "b", "c", "d", "a", "b", "c", "d"] a = [] {foo: 0, bar: 1, baz: 2}.cycle(2) {|element| a.push(element) } a # => [[:foo, 0], [:bar, 1], [:baz, 2], [:foo, 0], [:bar, 1], [:baz, 2]]
If count is zero or negative, does not call the block.
When called with a block and n is nil, cycles forever.
When no block is given, returns an Enumerator.
Each element in the returned enumerator is a 2-element array consisting of:
A value returned by the block.
An array (“chunk”) containing the element for which that value was returned, and all following elements for which the block returned the same value:
So that:
Each block return value that is different from its predecessor begins a new chunk.
Each block return value that is the same as its predecessor continues the same chunk.
Example:
e = (0..10).chunk {|i| (i / 3).floor } # => #<Enumerator: ...> # The enumerator elements. e.next # => [0, [0, 1, 2]] e.next # => [1, [3, 4, 5]] e.next # => [2, [6, 7, 8]] e.next # => [3, [9, 10]]
Method chunk is especially useful for an enumerable that is already sorted. This example counts words for each initial letter in a large array of words:
# Get sorted words from a web page. url = 'https://raw.githubusercontent.com/eneko/data-repository/master/data/words.txt' words = URI::open(url).readlines # Make chunks, one for each letter. e = words.chunk {|word| word.upcase[0] } # => #<Enumerator: ...> # Display 'A' through 'F'. e.each {|c, words| p [c, words.length]; break if c == 'F' }
Output:
["A", 17096] ["B", 11070] ["C", 19901] ["D", 10896] ["E", 8736] ["F", 6860]
You can use the special symbol :_alone to force an element into its own separate chuck:
a = [0, 0, 1, 1] e = a.chunk{|i| i.even? ? :_alone : true } e.to_a # => [[:_alone, [0]], [:_alone, [0]], [true, [1, 1]]]
For example, you can put each line that contains a URL into its own chunk:
pattern = /http/ open(filename) { |f| f.chunk { |line| line =~ pattern ? :_alone : true }.each { |key, lines| pp lines } }
You can use the special symbol :_separator or nil to force an element to be ignored (not included in any chunk):
a = [0, 0, -1, 1, 1] e = a.chunk{|i| i < 0 ? :_separator : true } e.to_a # => [[true, [0, 0]], [true, [1, 1]]]
Note that the separator does end the chunk:
a = [0, 0, -1, 1, -1, 1] e = a.chunk{|i| i < 0 ? :_separator : true } e.to_a # => [[true, [0, 0]], [true, [1]], [true, [1]]]
For example, the sequence of hyphens in svn log can be eliminated as follows:
sep = "-"*72 + "\n" IO.popen("svn log README") { |f| f.chunk { |line| line != sep || nil }.each { |_, lines| pp lines } } #=> ["r20018 | knu | 2008-10-29 13:20:42 +0900 (Wed, 29 Oct 2008) | 2 lines\n", # "\n", # "* README, README.ja: Update the portability section.\n", # "\n"] # ["r16725 | knu | 2008-05-31 23:34:23 +0900 (Sat, 31 May 2008) | 2 lines\n", # "\n", # "* README, README.ja: Add a note about default C flags.\n", # "\n"] # ...
Paragraphs separated by empty lines can be parsed as follows:
File.foreach("README").chunk { |line| /\A\s*\z/ !~ line || nil }.each { |_, lines| pp lines }
Returns an enumerator object generated from this enumerator and given enumerables.
e = (1..3).chain([4, 5]) e.to_a #=> [1, 2, 3, 4, 5]
Returns system configuration directory.
This is typically “/etc”, but is modified by the prefix used when Ruby was compiled. For example, if Ruby is built and installed in /usr/local, returns “/usr/local/etc” on other platforms than Windows. On Windows, this always returns the directory provided by the system.
Returns system temporary directory; typically “/tmp”.
Returns system configuration variable using sysconf().
name should be a constant under Etc which begins with SC_.
The return value is an integer or nil. nil means indefinite limit. (sysconf() returns -1 but errno is not set.)
Etc.sysconf(Etc::SC_ARG_MAX) #=> 2097152 Etc.sysconf(Etc::SC_LOGIN_NAME_MAX) #=> 256
Checks the status of the child process specified by pid. Returns nil if the process is still alive.
If the process is not alive, and raise was true, a PTY::ChildExited exception will be raised. Otherwise it will return a Process::Status instance.
pidThe process id of the process to check
raiseIf true and the process identified by pid is no longer alive a PTY::ChildExited is raised.
Returns true if the named file is a symbolic link.
Returns true if the named file is a character device.
file_name can be an IO object.
Invokes the block with a Benchmark::Report object, which may be used to collect and report on the results of individual benchmark tests. Reserves label_width leading spaces for labels on each line. Prints caption at the top of the report, and uses format to format each line. (Note: caption must contain a terminating newline character, see the default Benchmark::Tms::CAPTION for an example.)
Returns an array of Benchmark::Tms objects.
If the block returns an array of Benchmark::Tms objects, these will be used to format additional lines of output. If labels parameter are given, these are used to label these extra lines.
Note: Other methods provide a simpler interface to this one, and are suitable for nearly all benchmarking requirements. See the examples in Benchmark, and the bm and bmbm methods.
Example:
require 'benchmark' include Benchmark # we need the CAPTION and FORMAT constants n = 5000000 Benchmark.benchmark(CAPTION, 7, FORMAT, ">total:", ">avg:") do |x| tf = x.report("for:") { for i in 1..n; a = "1"; end } tt = x.report("times:") { n.times do ; a = "1"; end } tu = x.report("upto:") { 1.upto(n) do ; a = "1"; end } [tf+tt+tu, (tf+tt+tu)/3] end
Generates:
user system total real for: 0.970000 0.000000 0.970000 ( 0.970493) times: 0.990000 0.000000 0.990000 ( 0.989542) upto: 0.970000 0.000000 0.970000 ( 0.972854) >total: 2.930000 0.000000 2.930000 ( 2.932889) >avg: 0.976667 0.000000 0.976667 ( 0.977630)
Invokes the block with a Benchmark::Report object, which may be used to collect and report on the results of individual benchmark tests. Reserves label_width leading spaces for labels on each line. Prints caption at the top of the report, and uses format to format each line. (Note: caption must contain a terminating newline character, see the default Benchmark::Tms::CAPTION for an example.)
Returns an array of Benchmark::Tms objects.
If the block returns an array of Benchmark::Tms objects, these will be used to format additional lines of output. If labels parameter are given, these are used to label these extra lines.
Note: Other methods provide a simpler interface to this one, and are suitable for nearly all benchmarking requirements. See the examples in Benchmark, and the bm and bmbm methods.
Example:
require 'benchmark' include Benchmark # we need the CAPTION and FORMAT constants n = 5000000 Benchmark.benchmark(CAPTION, 7, FORMAT, ">total:", ">avg:") do |x| tf = x.report("for:") { for i in 1..n; a = "1"; end } tt = x.report("times:") { n.times do ; a = "1"; end } tu = x.report("upto:") { 1.upto(n) do ; a = "1"; end } [tf+tt+tu, (tf+tt+tu)/3] end
Generates:
user system total real for: 0.970000 0.000000 0.970000 ( 0.970493) times: 0.990000 0.000000 0.990000 ( 0.989542) upto: 0.970000 0.000000 0.970000 ( 0.972854) >total: 2.930000 0.000000 2.930000 ( 2.932889) >avg: 0.976667 0.000000 0.976667 ( 0.977630)
Changes permission bits on the named files (in list) to the bit pattern represented by mode.
mode is the symbolic and absolute mode can be used.
Absolute mode is
FileUtils.chmod 0755, 'somecommand' FileUtils.chmod 0644, %w(my.rb your.rb his.rb her.rb) FileUtils.chmod 0755, '/usr/bin/ruby', verbose: true
Symbolic mode is
FileUtils.chmod "u=wrx,go=rx", 'somecommand' FileUtils.chmod "u=wr,go=rr", %w(my.rb your.rb his.rb her.rb) FileUtils.chmod "u=wrx,go=rx", '/usr/bin/ruby', verbose: true
is user, group, other mask.
is user’s mask.
is group’s mask.
is other’s mask.
is write permission.
is read permission.
is execute permission.
is execute permission for directories only, must be used in conjunction with “+”
is uid, gid.
is sticky bit.
is added to a class given the specified mode.
Is removed from a given class given mode.
Is the exact nature of the class will be given a specified mode.
Changes permission bits on the named files (in list) to the bit pattern represented by mode.
mode is the symbolic and absolute mode can be used.
Absolute mode is
FileUtils.chmod 0755, 'somecommand' FileUtils.chmod 0644, %w(my.rb your.rb his.rb her.rb) FileUtils.chmod 0755, '/usr/bin/ruby', verbose: true
Symbolic mode is
FileUtils.chmod "u=wrx,go=rx", 'somecommand' FileUtils.chmod "u=wr,go=rr", %w(my.rb your.rb his.rb her.rb) FileUtils.chmod "u=wrx,go=rx", '/usr/bin/ruby', verbose: true
is user, group, other mask.
is user’s mask.
is group’s mask.
is other’s mask.
is write permission.
is read permission.
is execute permission.
is execute permission for directories only, must be used in conjunction with “+”
is uid, gid.
is sticky bit.
is added to a class given the specified mode.
Is removed from a given class given mode.
Is the exact nature of the class will be given a specified mode.
Changes permission bits on the named files (in list) to the bit pattern represented by mode.
FileUtils.chmod_R 0700, "/tmp/app.#{$$}" FileUtils.chmod_R "u=wrx", "/tmp/app.#{$$}"
Changes permission bits on the named files (in list) to the bit pattern represented by mode.
FileUtils.chmod_R 0700, "/tmp/app.#{$$}" FileUtils.chmod_R "u=wrx", "/tmp/app.#{$$}"