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
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]
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.
pid
The process id of the process to check
raise
If true and the process identified by pid is no longer alive a PTY::ChildExited is raised.
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.#{$$}" FileUtils.chmod_R "u=wrx", "/tmp/app.#{$$}"
Changes owner and group on the named files (in list) to the user user and the group group. user and group may be an ID (Integer/String) or a name (String). If user or group is nil, this method does not change the attribute.
FileUtils.chown 'root', 'staff', '/usr/local/bin/ruby' FileUtils.chown nil, 'bin', Dir.glob('/usr/bin/*'), verbose: true
Changes owner and group on the named files (in list) to the user user and the group group. user and group may be an ID (Integer/String) or a name (String). If user or group is nil, this method does not change the attribute.
FileUtils.chown 'root', 'staff', '/usr/local/bin/ruby' FileUtils.chown nil, 'bin', Dir.glob('/usr/bin/*'), verbose: true
Changes owner and group on the named files (in list) to the user user and the group group recursively. user and group may be an ID (Integer/String) or a name (String). If user or group is nil, this method does not change the attribute.
FileUtils.chown_R 'www', 'www', '/var/www/htdocs' FileUtils.chown_R 'cvs', 'cvs', '/var/cvs', verbose: true
Changes owner and group on the named files (in list) to the user user and the group group recursively. user and group may be an ID (Integer/String) or a name (String). If user or group is nil, this method does not change the attribute.
FileUtils.chown_R 'www', 'www', '/var/www/htdocs' FileUtils.chown_R 'cvs', 'cvs', '/var/cvs', verbose: true
Updates modification time (mtime) and access time (atime) of file(s) in list. Files are created if they don’t exist.
FileUtils.touch 'timestamp' FileUtils.touch Dir.glob('*.c'); system 'make'
Updates modification time (mtime) and access time (atime) of file(s) in list. Files are created if they don’t exist.
FileUtils.touch 'timestamp' FileUtils.touch Dir.glob('*.c'); system 'make'
Set the changed state of this object. Notifications will be sent only if the changed state is true.
state
Boolean indicating the changed state of this Observable.
Returns true if this object’s state has been changed since the last notify_observers call.
Some operating systems retain the status of terminated child processes until the parent collects that status (normally using some variant of wait()). If the parent never collects this status, the child stays around as a zombie process. Process::detach prevents this by setting up a separate Ruby thread whose sole job is to reap the status of the process pid when it terminates. Use detach only when you do not intend to explicitly wait for the child to terminate.
The waiting thread returns the exit status of the detached process when it terminates, so you can use Thread#join to know the result. If specified pid is not a valid child process ID, the thread returns nil immediately.
The waiting thread has pid method which returns the pid.
In this first example, we don’t reap the first child process, so it appears as a zombie in the process status display.
p1 = fork { sleep 0.1 } p2 = fork { sleep 0.2 } Process.waitpid(p2) sleep 2 system("ps -ho pid,state -p #{p1}")
produces:
27389 Z
In the next example, Process::detach is used to reap the child automatically.
p1 = fork { sleep 0.1 } p2 = fork { sleep 0.2 } Process.detach(p1) Process.waitpid(p2) sleep 2 system("ps -ho pid,state -p #{p1}")
(produces no output)