This is a convenience method which is same as follows:
begin q = PrettyPrint.new(output, maxwidth, newline, &genspace) ... q.flush output end
Creates a temporary file as a usual File object (not a Tempfile). It does not use finalizer and delegation, which makes it more efficient and reliable.
If no block is given, this is similar to Tempfile.new except creating File instead of Tempfile. In that case, the created file is not removed automatically. You should use File.unlink to remove it.
If a block is given, then a File object will be constructed, and the block is invoked with the object as the argument. The File object will be automatically closed and the temporary file is removed after the block terminates, releasing all resources that the block created. The call returns the value of the block.
In any case, all arguments (basename, tmpdir, mode, and **options) will be treated the same as for Tempfile.new.
Tempfile.create('foo', '/home/temp') do |f| # ... do something with f ... end
Returns true if a Proc object is lambda. false if non-lambda.
The lambda-ness affects argument handling and the behavior of return and break.
A Proc object generated by proc ignores extra arguments.
proc {|a,b| [a,b] }.call(1,2,3) #=> [1,2]
It provides nil for missing arguments.
proc {|a,b| [a,b] }.call(1) #=> [1,nil]
It expands a single array argument.
proc {|a,b| [a,b] }.call([1,2]) #=> [1,2]
A Proc object generated by lambda doesn’t have such tricks.
lambda {|a,b| [a,b] }.call(1,2,3) #=> ArgumentError lambda {|a,b| [a,b] }.call(1) #=> ArgumentError lambda {|a,b| [a,b] }.call([1,2]) #=> ArgumentError
Proc#lambda? is a predicate for the tricks. It returns true if no tricks apply.
lambda {}.lambda? #=> true proc {}.lambda? #=> false
Proc.new is the same as proc.
Proc.new {}.lambda? #=> false
lambda, proc and Proc.new preserve the tricks of a Proc object given by & argument.
lambda(&lambda {}).lambda? #=> true proc(&lambda {}).lambda? #=> true Proc.new(&lambda {}).lambda? #=> true lambda(&proc {}).lambda? #=> false proc(&proc {}).lambda? #=> false Proc.new(&proc {}).lambda? #=> false
A Proc object generated by & argument has the tricks
def n(&b) b.lambda? end n {} #=> false
The & argument preserves the tricks if a Proc object is given by & argument.
n(&lambda {}) #=> true n(&proc {}) #=> false n(&Proc.new {}) #=> false
A Proc object converted from a method has no tricks.
def m() end method(:m).to_proc.lambda? #=> true n(&method(:m)) #=> true n(&method(:m).to_proc) #=> true
define_method is treated the same as method definition. The defined method has no tricks.
class C define_method(:d) {} end C.new.d(1,2) #=> ArgumentError C.new.method(:d).to_proc.lambda? #=> true
define_method always defines a method without the tricks, even if a non-lambda Proc object is given. This is the only exception for which the tricks are not preserved.
class C define_method(:e, &proc {}) end C.new.e(1,2) #=> ArgumentError C.new.method(:e).to_proc.lambda? #=> true
This exception ensures that methods never have tricks and makes it easy to have wrappers to define methods that behave as usual.
class C def self.def2(name, &body) define_method(name, &body) end def2(:f) {} end C.new.f(1,2) #=> ArgumentError
The wrapper def2 defines a method which has no tricks.
Returns whether the method is private.
Returns whether the method is private.
Give the thread scheduler a hint to pass execution to another thread. A running thread may or may not switch, it depends on OS and processor.
Returns the status of thr.
"sleep"
Returned if this thread is sleeping or waiting on I/O
"run"
When this thread is executing
"aborting"
If this thread is aborting
false
When this thread is terminated normally
nil
If terminated with an exception.
a = Thread.new { raise("die now") } b = Thread.new { Thread.stop } c = Thread.new { Thread.exit } d = Thread.new { sleep } d.kill #=> #<Thread:0x401b3678 aborting> a.status #=> nil b.status #=> "sleep" c.status #=> false d.status #=> "aborting" Thread.current.status #=> "run"
Returns internal information of TracePoint.
The contents of the returned value are implementation specific. It may be changed in future.
This method is only for debugging TracePoint itself.
Activates the trace.
Returns true if trace was enabled. Returns false if trace was disabled.
trace.enabled? #=> false trace.enable #=> false (previous state) # trace is enabled trace.enabled? #=> true trace.enable #=> true (previous state) # trace is still enabled
If a block is given, the trace will only be enabled within the scope of the block.
trace.enabled? #=> false trace.enable do trace.enabled? # only enabled for this block end trace.enabled? #=> false
target, target_line and target_thread parameters are used to limit tracing only to specified code objects. target should be a code object for which RubyVM::InstructionSequence.of will return an instruction sequence.
t = TracePoint.new(:line) { |tp| p tp } def m1 p 1 end def m2 p 2 end t.enable(target: method(:m1)) m1 # prints #<TracePoint:line test.rb:4 in `m1'> m2 # prints nothing
Note: You cannot access event hooks within the enable block.
trace.enable { p tp.lineno } #=> RuntimeError: access from outside
The current status of the trace
In (min, max) form, returns min if obj <=> min is less than zero, max if obj <=> max is greater than zero, and obj otherwise.
12.clamp(0, 100) #=> 12 523.clamp(0, 100) #=> 100 -3.123.clamp(0, 100) #=> 0 'd'.clamp('a', 'f') #=> 'd' 'z'.clamp('a', 'f') #=> 'f'
In (range) form, returns range.begin if obj <=> range.begin is less than zero, range.end if obj <=> range.end is greater than zero, and obj otherwise.
12.clamp(0..100) #=> 12 523.clamp(0..100) #=> 100 -3.123.clamp(0..100) #=> 0 'd'.clamp('a'..'f') #=> 'd' 'z'.clamp('a'..'f') #=> 'f'
If range.begin is nil, it is considered smaller than obj, and if range.end is nil, it is considered greater than obj.
-20.clamp(0..) #=> 0 523.clamp(..100) #=> 100
When range.end is excluded and not nil, an exception is raised.
100.clamp(0...100) # ArgumentError
Yields self to the block and returns the result of the block.
3.next.then {|x| x**x }.to_s #=> "256"
Good usage for then is value piping in method chains:
require 'open-uri' require 'json' construct_url(arguments). then {|url| URI(url).read }. then {|response| JSON.parse(response) }
When called without block, the method returns Enumerator, which can be used, for example, for conditional circuit-breaking:
# meets condition, no-op 1.then.detect(&:odd?) # => 1 # does not meet condition, drop value 2.then.detect(&:odd?) # => nil
Returns arg converted to a float. Numeric types are converted directly, and with exception to String and nil the rest are converted using arg.to_f. Converting a String with invalid characters will result in a ArgumentError. Converting nil generates a TypeError. Exceptions can be suppressed by passing exception: false.
Float(1) #=> 1.0 Float("123.456") #=> 123.456 Float("123.0_badstring") #=> ArgumentError: invalid value for Float(): "123.0_badstring" Float(nil) #=> TypeError: can't convert nil into Float Float("123.0_badstring", exception: false) #=> nil
Returns the string resulting from applying format_string to any additional arguments. Within the format string, any characters other than format sequences are copied to the result.
The syntax of a format sequence is as follows.
%[flags][width][.precision]type
A format sequence consists of a percent sign, followed by optional flags, width, and precision indicators, then terminated with a field type character. The field type controls how the corresponding sprintf argument is to be interpreted, while the flags modify that interpretation.
The field type characters are:
Field | Integer Format
------+--------------------------------------------------------------
b | Convert argument as a binary number.
| Negative numbers will be displayed as a two's complement
| prefixed with `..1'.
B | Equivalent to `b', but uses an uppercase 0B for prefix
| in the alternative format by #.
d | Convert argument as a decimal number.
i | Identical to `d'.
o | Convert argument as an octal number.
| Negative numbers will be displayed as a two's complement
| prefixed with `..7'.
u | Identical to `d'.
x | Convert argument as a hexadecimal number.
| Negative numbers will be displayed as a two's complement
| prefixed with `..f' (representing an infinite string of
| leading 'ff's).
X | Equivalent to `x', but uses uppercase letters.
Field | Float Format
------+--------------------------------------------------------------
e | Convert floating point argument into exponential notation
| with one digit before the decimal point as [-]d.dddddde[+-]dd.
| The precision specifies the number of digits after the decimal
| point (defaulting to six).
E | Equivalent to `e', but uses an uppercase E to indicate
| the exponent.
f | Convert floating point argument as [-]ddd.dddddd,
| where the precision specifies the number of digits after
| the decimal point.
g | Convert a floating point number using exponential form
| if the exponent is less than -4 or greater than or
| equal to the precision, or in dd.dddd form otherwise.
| The precision specifies the number of significant digits.
G | Equivalent to `g', but use an uppercase `E' in exponent form.
a | Convert floating point argument as [-]0xh.hhhhp[+-]dd,
| which is consisted from optional sign, "0x", fraction part
| as hexadecimal, "p", and exponential part as decimal.
A | Equivalent to `a', but use uppercase `X' and `P'.
Field | Other Format
------+--------------------------------------------------------------
c | Argument is the numeric code for a single character or
| a single character string itself.
p | The valuing of argument.inspect.
s | Argument is a string to be substituted. If the format
| sequence contains a precision, at most that many characters
| will be copied.
% | A percent sign itself will be displayed. No argument taken.
The flags modifies the behavior of the formats. The flag characters are:
Flag | Applies to | Meaning
---------+---------------+-----------------------------------------
space | bBdiouxX | Leave a space at the start of
| aAeEfgG | non-negative numbers.
| (numeric fmt) | For `o', `x', `X', `b' and `B', use
| | a minus sign with absolute value for
| | negative values.
---------+---------------+-----------------------------------------
(digit)$ | all | Specifies the absolute argument number
| | for this field. Absolute and relative
| | argument numbers cannot be mixed in a
| | sprintf string.
---------+---------------+-----------------------------------------
# | bBoxX | Use an alternative format.
| aAeEfgG | For the conversions `o', increase the precision
| | until the first digit will be `0' if
| | it is not formatted as complements.
| | For the conversions `x', `X', `b' and `B'
| | on non-zero, prefix the result with ``0x'',
| | ``0X'', ``0b'' and ``0B'', respectively.
| | For `a', `A', `e', `E', `f', `g', and 'G',
| | force a decimal point to be added,
| | even if no digits follow.
| | For `g' and 'G', do not remove trailing zeros.
---------+---------------+-----------------------------------------
+ | bBdiouxX | Add a leading plus sign to non-negative
| aAeEfgG | numbers.
| (numeric fmt) | For `o', `x', `X', `b' and `B', use
| | a minus sign with absolute value for
| | negative values.
---------+---------------+-----------------------------------------
- | all | Left-justify the result of this conversion.
---------+---------------+-----------------------------------------
0 (zero) | bBdiouxX | Pad with zeros, not spaces.
| aAeEfgG | For `o', `x', `X', `b' and `B', radix-1
| (numeric fmt) | is used for negative numbers formatted as
| | complements.
---------+---------------+-----------------------------------------
* | all | Use the next argument as the field width.
| | If negative, left-justify the result. If the
| | asterisk is followed by a number and a dollar
| | sign, use the indicated argument as the width.
Examples of flags:
# `+' and space flag specifies the sign of non-negative numbers. sprintf("%d", 123) #=> "123" sprintf("%+d", 123) #=> "+123" sprintf("% d", 123) #=> " 123" # `#' flag for `o' increases number of digits to show `0'. # `+' and space flag changes format of negative numbers. sprintf("%o", 123) #=> "173" sprintf("%#o", 123) #=> "0173" sprintf("%+o", -123) #=> "-173" sprintf("%o", -123) #=> "..7605" sprintf("%#o", -123) #=> "..7605" # `#' flag for `x' add a prefix `0x' for non-zero numbers. # `+' and space flag disables complements for negative numbers. sprintf("%x", 123) #=> "7b" sprintf("%#x", 123) #=> "0x7b" sprintf("%+x", -123) #=> "-7b" sprintf("%x", -123) #=> "..f85" sprintf("%#x", -123) #=> "0x..f85" sprintf("%#x", 0) #=> "0" # `#' for `X' uses the prefix `0X'. sprintf("%X", 123) #=> "7B" sprintf("%#X", 123) #=> "0X7B" # `#' flag for `b' add a prefix `0b' for non-zero numbers. # `+' and space flag disables complements for negative numbers. sprintf("%b", 123) #=> "1111011" sprintf("%#b", 123) #=> "0b1111011" sprintf("%+b", -123) #=> "-1111011" sprintf("%b", -123) #=> "..10000101" sprintf("%#b", -123) #=> "0b..10000101" sprintf("%#b", 0) #=> "0" # `#' for `B' uses the prefix `0B'. sprintf("%B", 123) #=> "1111011" sprintf("%#B", 123) #=> "0B1111011" # `#' for `e' forces to show the decimal point. sprintf("%.0e", 1) #=> "1e+00" sprintf("%#.0e", 1) #=> "1.e+00" # `#' for `f' forces to show the decimal point. sprintf("%.0f", 1234) #=> "1234" sprintf("%#.0f", 1234) #=> "1234." # `#' for `g' forces to show the decimal point. # It also disables stripping lowest zeros. sprintf("%g", 123.4) #=> "123.4" sprintf("%#g", 123.4) #=> "123.400" sprintf("%g", 123456) #=> "123456" sprintf("%#g", 123456) #=> "123456."
The field width is an optional integer, followed optionally by a period and a precision. The width specifies the minimum number of characters that will be written to the result for this field.
Examples of width:
# padding is done by spaces, width=20 # 0 or radix-1. <------------------> sprintf("%20d", 123) #=> " 123" sprintf("%+20d", 123) #=> " +123" sprintf("%020d", 123) #=> "00000000000000000123" sprintf("%+020d", 123) #=> "+0000000000000000123" sprintf("% 020d", 123) #=> " 0000000000000000123" sprintf("%-20d", 123) #=> "123 " sprintf("%-+20d", 123) #=> "+123 " sprintf("%- 20d", 123) #=> " 123 " sprintf("%020x", -123) #=> "..ffffffffffffffff85"
For numeric fields, the precision controls the number of decimal places displayed. For string fields, the precision determines the maximum number of characters to be copied from the string. (Thus, the format sequence %10.10s will always contribute exactly ten characters to the result.)
Examples of precisions:
# precision for `d', 'o', 'x' and 'b' is # minimum number of digits <------> sprintf("%20.8d", 123) #=> " 00000123" sprintf("%20.8o", 123) #=> " 00000173" sprintf("%20.8x", 123) #=> " 0000007b" sprintf("%20.8b", 123) #=> " 01111011" sprintf("%20.8d", -123) #=> " -00000123" sprintf("%20.8o", -123) #=> " ..777605" sprintf("%20.8x", -123) #=> " ..ffff85" sprintf("%20.8b", -11) #=> " ..110101" # "0x" and "0b" for `#x' and `#b' is not counted for # precision but "0" for `#o' is counted. <------> sprintf("%#20.8d", 123) #=> " 00000123" sprintf("%#20.8o", 123) #=> " 00000173" sprintf("%#20.8x", 123) #=> " 0x0000007b" sprintf("%#20.8b", 123) #=> " 0b01111011" sprintf("%#20.8d", -123) #=> " -00000123" sprintf("%#20.8o", -123) #=> " ..777605" sprintf("%#20.8x", -123) #=> " 0x..ffff85" sprintf("%#20.8b", -11) #=> " 0b..110101" # precision for `e' is number of # digits after the decimal point <------> sprintf("%20.8e", 1234.56789) #=> " 1.23456789e+03" # precision for `f' is number of # digits after the decimal point <------> sprintf("%20.8f", 1234.56789) #=> " 1234.56789000" # precision for `g' is number of # significant digits <-------> sprintf("%20.8g", 1234.56789) #=> " 1234.5679" # <-------> sprintf("%20.8g", 123456789) #=> " 1.2345679e+08" # precision for `s' is # maximum number of characters <------> sprintf("%20.8s", "string test") #=> " string t"
Examples:
sprintf("%d %04x", 123, 123) #=> "123 007b" sprintf("%08b '%4s'", 123, 123) #=> "01111011 ' 123'" sprintf("%1$*2$s %2$d %1$s", "hello", 8) #=> " hello 8 hello" sprintf("%1$*2$s %2$d", "hello", -8) #=> "hello -8" sprintf("%+g:% g:%-g", 1.23, 1.23, 1.23) #=> "+1.23: 1.23:1.23" sprintf("%u", -123) #=> "-123"
For more complex formatting, Ruby supports a reference by name. %<name>s style uses format style, but %{name} style doesn’t.
Examples:
sprintf("%<foo>d : %<bar>f", { :foo => 1, :bar => 2 }) #=> 1 : 2.000000 sprintf("%{foo}f", { :foo => 1 }) # => "1f"
Equivalent to Proc.new, except the resulting Proc objects check the number of parameters passed when called.
spawn executes specified command and return its pid.
pid = spawn("tar xf ruby-2.0.0-p195.tar.bz2") Process.wait pid pid = spawn(RbConfig.ruby, "-eputs'Hello, world!'") Process.wait pid
This method is similar to Kernel#system but it doesn’t wait for the command to finish.
The parent process should use Process.wait to collect the termination status of its child or use Process.detach to register disinterest in their status; otherwise, the operating system may accumulate zombie processes.
spawn has bunch of options to specify process attributes:
env: hash
name => val : set the environment variable
name => nil : unset the environment variable
the keys and the values except for +nil+ must be strings.
command...:
commandline : command line string which is passed to the standard shell
cmdname, arg1, ... : command name and one or more arguments (This form does not use the shell. See below for caveats.)
[cmdname, argv0], arg1, ... : command name, argv[0] and zero or more arguments (no shell)
options: hash
clearing environment variables:
:unsetenv_others => true : clear environment variables except specified by env
:unsetenv_others => false : don't clear (default)
process group:
:pgroup => true or 0 : make a new process group
:pgroup => pgid : join the specified process group
:pgroup => nil : don't change the process group (default)
create new process group: Windows only
:new_pgroup => true : the new process is the root process of a new process group
:new_pgroup => false : don't create a new process group (default)
resource limit: resourcename is core, cpu, data, etc. See Process.setrlimit.
:rlimit_resourcename => limit
:rlimit_resourcename => [cur_limit, max_limit]
umask:
:umask => int
redirection:
key:
FD : single file descriptor in child process
[FD, FD, ...] : multiple file descriptor in child process
value:
FD : redirect to the file descriptor in parent process
string : redirect to file with open(string, "r" or "w")
[string] : redirect to file with open(string, File::RDONLY)
[string, open_mode] : redirect to file with open(string, open_mode, 0644)
[string, open_mode, perm] : redirect to file with open(string, open_mode, perm)
[:child, FD] : redirect to the redirected file descriptor
:close : close the file descriptor in child process
FD is one of follows
:in : the file descriptor 0 which is the standard input
:out : the file descriptor 1 which is the standard output
:err : the file descriptor 2 which is the standard error
integer : the file descriptor of specified the integer
io : the file descriptor specified as io.fileno
file descriptor inheritance: close non-redirected non-standard fds (3, 4, 5, ...) or not
:close_others => false : inherit
current directory:
:chdir => str
The cmdname, arg1, ... form does not use the shell. However, on different OSes, different things are provided as built-in commands. An example of this is +‘echo’+, which is a built-in on Windows, but is a normal program on Linux and Mac OS X. This means that Process.spawn 'echo', '%Path%' will display the contents of the %Path% environment variable on Windows, but Process.spawn 'echo', '$PATH' prints the literal $PATH.
If a hash is given as env, the environment is updated by env before exec(2) in the child process. If a pair in env has nil as the value, the variable is deleted.
# set FOO as BAR and unset BAZ. pid = spawn({"FOO"=>"BAR", "BAZ"=>nil}, command)
If a hash is given as options, it specifies process group, create new process group, resource limit, current directory, umask and redirects for the child process. Also, it can be specified to clear environment variables.
The :unsetenv_others key in options specifies to clear environment variables, other than specified by env.
pid = spawn(command, :unsetenv_others=>true) # no environment variable pid = spawn({"FOO"=>"BAR"}, command, :unsetenv_others=>true) # FOO only
The :pgroup key in options specifies a process group. The corresponding value should be true, zero, a positive integer, or nil. true and zero cause the process to be a process leader of a new process group. A non-zero positive integer causes the process to join the provided process group. The default value, nil, causes the process to remain in the same process group.
pid = spawn(command, :pgroup=>true) # process leader pid = spawn(command, :pgroup=>10) # belongs to the process group 10
The :new_pgroup key in options specifies to pass CREATE_NEW_PROCESS_GROUP flag to CreateProcessW() that is Windows API. This option is only for Windows. true means the new process is the root process of the new process group. The new process has CTRL+C disabled. This flag is necessary for Process.kill(:SIGINT, pid) on the subprocess. :new_pgroup is false by default.
pid = spawn(command, :new_pgroup=>true) # new process group pid = spawn(command, :new_pgroup=>false) # same process group
The :rlimit_foo key specifies a resource limit. foo should be one of resource types such as core. The corresponding value should be an integer or an array which have one or two integers: same as cur_limit and max_limit arguments for Process.setrlimit.
cur, max = Process.getrlimit(:CORE) pid = spawn(command, :rlimit_core=>[0,max]) # disable core temporary. pid = spawn(command, :rlimit_core=>max) # enable core dump pid = spawn(command, :rlimit_core=>0) # never dump core.
The :umask key in options specifies the umask.
pid = spawn(command, :umask=>077)
The :in, :out, :err, an integer, an IO and an array key specifies a redirection. The redirection maps a file descriptor in the child process.
For example, stderr can be merged into stdout as follows:
pid = spawn(command, :err=>:out) pid = spawn(command, 2=>1) pid = spawn(command, STDERR=>:out) pid = spawn(command, STDERR=>STDOUT)
The hash keys specifies a file descriptor in the child process started by spawn. :err, 2 and STDERR specifies the standard error stream (stderr).
The hash values specifies a file descriptor in the parent process which invokes spawn. :out, 1 and STDOUT specifies the standard output stream (stdout).
In the above example, the standard output in the child process is not specified. So it is inherited from the parent process.
The standard input stream (stdin) can be specified by :in, 0 and STDIN.
A filename can be specified as a hash value.
pid = spawn(command, :in=>"/dev/null") # read mode pid = spawn(command, :out=>"/dev/null") # write mode pid = spawn(command, :err=>"log") # write mode pid = spawn(command, [:out, :err]=>"/dev/null") # write mode pid = spawn(command, 3=>"/dev/null") # read mode
For stdout and stderr (and combination of them), it is opened in write mode. Otherwise read mode is used.
For specifying flags and permission of file creation explicitly, an array is used instead.
pid = spawn(command, :in=>["file"]) # read mode is assumed pid = spawn(command, :in=>["file", "r"]) pid = spawn(command, :out=>["log", "w"]) # 0644 assumed pid = spawn(command, :out=>["log", "w", 0600]) pid = spawn(command, :out=>["log", File::WRONLY|File::EXCL|File::CREAT, 0600])
The array specifies a filename, flags and permission. The flags can be a string or an integer. If the flags is omitted or nil, File::RDONLY is assumed. The permission should be an integer. If the permission is omitted or nil, 0644 is assumed.
If an array of IOs and integers are specified as a hash key, all the elements are redirected.
# stdout and stderr is redirected to log file. # The file "log" is opened just once. pid = spawn(command, [:out, :err]=>["log", "w"])
Another way to merge multiple file descriptors is [:child, fd]. [:child, fd] means the file descriptor in the child process. This is different from fd. For example, :err=>:out means redirecting child stderr to parent stdout. But :err=>[:child, :out] means redirecting child stderr to child stdout. They differ if stdout is redirected in the child process as follows.
# stdout and stderr is redirected to log file. # The file "log" is opened just once. pid = spawn(command, :out=>["log", "w"], :err=>[:child, :out])
[:child, :out] can be used to merge stderr into stdout in IO.popen. In this case, IO.popen redirects stdout to a pipe in the child process and [:child, :out] refers the redirected stdout.
io = IO.popen(["sh", "-c", "echo out; echo err >&2", :err=>[:child, :out]]) p io.read #=> "out\nerr\n"
The :chdir key in options specifies the current directory.
pid = spawn(command, :chdir=>"/var/tmp")
spawn closes all non-standard unspecified descriptors by default. The “standard” descriptors are 0, 1 and 2. This behavior is specified by :close_others option. :close_others doesn’t affect the standard descriptors which are closed only if :close is specified explicitly.
pid = spawn(command, :close_others=>true) # close 3,4,5,... (default) pid = spawn(command, :close_others=>false) # don't close 3,4,5,...
:close_others is false by default for spawn and IO.popen.
Note that fds which close-on-exec flag is already set are closed regardless of :close_others option.
So IO.pipe and spawn can be used as IO.popen.
# similar to r = IO.popen(command) r, w = IO.pipe pid = spawn(command, :out=>w) # r, w is closed in the child process. w.close
:close is specified as a hash value to close a fd individually.
f = open(foo) system(command, f=>:close) # don't inherit f.
If a file descriptor need to be inherited, io=>io can be used.
# valgrind has --log-fd option for log destination. # log_w=>log_w indicates log_w.fileno inherits to child process. log_r, log_w = IO.pipe pid = spawn("valgrind", "--log-fd=#{log_w.fileno}", "echo", "a", log_w=>log_w) log_w.close p log_r.read
It is also possible to exchange file descriptors.
pid = spawn(command, :out=>:err, :err=>:out)
The hash keys specify file descriptors in the child process. The hash values specifies file descriptors in the parent process. So the above specifies exchanging stdout and stderr. Internally, spawn uses an extra file descriptor to resolve such cyclic file descriptor mapping.
See Kernel.exec for the standard shell.
Deprecated. Use block_given? instead.
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
Transfers control to the end of the active catch block waiting for tag. Raises UncaughtThrowError if there is no catch block for the tag. The optional second parameter supplies a return value for the catch block, which otherwise defaults to nil. For examples, see Kernel::catch.
With a block given, returns an array of two arrays:
The first having those elements for which the block returns a truthy value.
The other having all other elements.
Examples:
p = (1..4).partition {|i| i.even? } p # => [[2, 4], [1, 3]] p = ('a'..'d').partition {|c| c < 'c' } p # => [["a", "b"], ["c", "d"]] h = {foo: 0, bar: 1, baz: 2, bat: 3} p = h.partition {|key, value| key.start_with?('b') } p # => [[[:bar, 1], [:baz, 2], [:bat, 3]], [[:foo, 0]]] p = h.partition {|key, value| value < 2 } p # => [[[:foo, 0], [:bar, 1]], [[:baz, 2], [:bat, 3]]]
With no block given, returns an Enumerator.
Related: Enumerable#group_by.
Returns whether for any element object == element:
(1..4).include?(2) # => true (1..4).include?(5) # => false (1..4).include?('2') # => false %w[a b c d].include?('b') # => true %w[a b c d].include?('2') # => false {foo: 0, bar: 1, baz: 2}.include?(:foo) # => true {foo: 0, bar: 1, baz: 2}.include?('foo') # => false {foo: 0, bar: 1, baz: 2}.include?(0) # => false
Enumerable#member? is an alias for Enumerable#include?.
Returns an array of all non-nil elements:
a = [nil, 0, nil, 'a', false, nil, false, nil, 'a', nil, 0, nil] a.compact # => [0, "a", false, false, "a", 0]
Computes the arctangent of decimal to the specified number of digits of precision, numeric.
If decimal is NaN, returns NaN.
BigMath.atan(BigDecimal('-1'), 16).to_s #=> "-0.785398163397448309615660845819878471907514682065e0"
Start/resume the coverage measurement.
Caveat: Currently, only process-global coverage measurement is supported. You cannot measure per-thread covearge. If your process has multiple thread, using Coverage.resume/suspend to capture code coverage executed from only a limited code block, may yield misleading results.