module Kernel
The Kernel module is included by class Object, so its methods are available in every Ruby object.
The Kernel instance methods are documented in class Object while the module methods are documented here. These methods are called without a receiver and thus can be called in functional form:
sprintf "%.1f", 1.234 #=> "1.2"
Public Class Methods
Returns uri converted to a URI object.
# File lib/uri/common.rb, line 992 def URI(uri) if uri.is_a?(URI::Generic) uri elsif uri = String.try_convert(uri) URI.parse(uri) else raise ArgumentError, "bad argument (expected URI object or URI string)" end end
Creates an IO object connected to the given stream, file, or subprocess.
If path does not start with a pipe character (|),
treat it as the name of a file to open using the specified mode (defaulting
to “r”).
The mode is either a string or an integer. If it is an
integer, it must be bitwise-or of open(2) flags, such as File::RDWR or
File::EXCL. If it is a string, it is either “fmode”, “fmode:ext_enc”, or
“fmode:ext_enc:int_enc”.
See the documentation of IO.new for full
documentation of the mode string directives.
If a file is being created, its initial permissions may be set using the
perm parameter. See File.new and the open(2) and chmod(2) man
pages for a description of permissions.
If a block is specified, it will be invoked with the IO object as a parameter, and the IO will be automatically closed when the block terminates. The call returns the value of the block.
If path starts with a pipe character
("|"), a subprocess is created, connected to the
caller by a pair of pipes. The returned IO object
may be used to write to the standard input and read from the standard
output of this subprocess.
If the command following the pipe is a single minus sign
("|-"), Ruby forks, and this subprocess is connected
to the parent. If the command is not "-", the
subprocess runs the command.
When the subprocess is ruby (opened via "|-"), the
open call returns nil. If a block is associated
with the open call, that block will run twice — once in the parent and once
in the child.
The block parameter will be an IO object in the
parent and nil in the child. The parent's IO
object will be connected to the child's $stdin and $stdout. The
subprocess will be terminated at the end of the block.
Examples¶ ↑
Reading from “testfile”:
open("testfile") do |f| print f.gets end
Produces:
This is line one
Open a subprocess and read its output:
cmd = open("|date") print cmd.gets cmd.close
Produces:
Wed Apr 9 08:56:31 CDT 2003
Open a subprocess running the same Ruby program:
f = open("|-", "w+") if f == nil puts "in Child" exit else puts "Got: #{f.gets}" end
Produces:
Got: in Child
Open a subprocess using a block to receive the IO object:
open "|-" do |f| if f then # parent process puts "Got: #{f.gets}" else # child process puts "in Child" end end
Produces:
Got: in Child
static VALUE
rb_f_open(int argc, VALUE *argv)
{
ID to_open = 0;
int redirect = FALSE;
if (argc >= 1) {
CONST_ID(to_open, "to_open");
if (rb_respond_to(argv[0], to_open)) {
redirect = TRUE;
}
else {
VALUE tmp = argv[0];
FilePathValue(tmp);
if (NIL_P(tmp)) {
redirect = TRUE;
}
else {
VALUE cmd = check_pipe_command(tmp);
if (!NIL_P(cmd)) {
argv[0] = cmd;
return rb_io_s_popen(argc, argv, rb_cIO);
}
}
}
}
if (redirect) {
VALUE io = rb_funcall2(argv[0], to_open, argc-1, argv+1);
if (rb_block_given_p()) {
return rb_ensure(rb_yield, io, io_close, io);
}
return io;
}
return rb_io_s_open(argc, argv, rb_cFile);
}
prints arguments in pretty form.
pp returns argument(s).
# File lib/pp.rb, line 13 def pp(*objs) # :doc: objs.each {|obj| PP.pp(obj) } objs.size <= 1 ? objs.first : objs end
Private Class Methods
Public Instance Methods
Returns arg as an Array.
First tries to call Array#to_ary
on arg, then Array#to_a.
Array(1..5) #=> [1, 2, 3, 4, 5]
static VALUE
rb_f_array(VALUE obj, VALUE arg)
{
return rb_Array(arg);
}
static VALUE
BigDecimal_global_new(int argc, VALUE *argv, VALUE self)
{
ENTER(1);
Real *pv;
GUARD_OBJ(pv, BigDecimal_new(argc, argv));
if (ToValue(pv)) pv = VpCopy(NULL, pv);
pv->obj = TypedData_Wrap_Struct(rb_cBigDecimal, &BigDecimal_data_type, pv);
return pv->obj;
}
Returns x+i*y;
Complex(1, 2) #=> (1+2i) Complex('1+2i') #=> (1+2i) Complex(nil) #=> TypeError Complex(1, nil) #=> TypeError
Syntax of string form:
string form = extra spaces , complex , extra spaces ;
complex = real part | [ sign ] , imaginary part
| real part , sign , imaginary part
| rational , "@" , rational ;
real part = rational ;
imaginary part = imaginary unit | unsigned rational , imaginary unit ;
rational = [ sign ] , unsigned rational ;
unsigned rational = numerator | numerator , "/" , denominator ;
numerator = integer part | fractional part | integer part , fractional part ;
denominator = digits ;
integer part = digits ;
fractional part = "." , digits , [ ( "e" | "E" ) , [ sign ] , digits ] ;
imaginary unit = "i" | "I" | "j" | "J" ;
sign = "-" | "+" ;
digits = digit , { digit | "_" , digit };
digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
extra spaces = ? \s* ? ;
See String#to_c.
static VALUE
nucomp_f_complex(int argc, VALUE *argv, VALUE klass)
{
return rb_funcall2(rb_cComplex, id_convert, argc, argv);
}
Returns arg converted to a float. Numeric types are converted directly, the rest are
converted using arg.to_f. As of Ruby 1.8, converting
nil generates a TypeError.
Float(1) #=> 1.0 Float("123.456") #=> 123.456
static VALUE
rb_f_float(VALUE obj, VALUE arg)
{
return rb_Float(arg);
}
Converts arg to a Hash by calling
arg.to_hash. Returns an empty Hash when
arg is nil or [].
Hash([]) #=> {} Hash(nil) #=> nil Hash(key: :value) #=> {:key => :value} Hash([1, 2, 3]) #=> TypeError
static VALUE
rb_f_hash(VALUE obj, VALUE arg)
{
return rb_Hash(arg);
}
Converts arg to a Fixnum or Bignum. Numeric types are converted directly (with floating
point numbers being truncated). base (0, or between 2 and 36)
is a base for integer string representation. If arg is a
String, when base is omitted or equals to zero, radix
indicators (0, 0b, and 0x) are
honored. In any case, strings should be strictly conformed to numeric
representation. This behavior is different from that of
String#to_i. Non string values will be converted using
to_int, and to_i. Passing nil raises
a TypeError.
Integer(123.999) #=> 123 Integer("0x1a") #=> 26 Integer(Time.new) #=> 1204973019 Integer("0930", 10) #=> 930 Integer("111", 2) #=> 7 Integer(nil) #=> TypeError
static VALUE
rb_f_integer(int argc, VALUE *argv, VALUE obj)
{
VALUE arg = Qnil;
int base = 0;
switch (argc) {
case 2:
base = NUM2INT(argv[1]);
case 1:
arg = argv[0];
break;
default:
/* should cause ArgumentError */
rb_scan_args(argc, argv, "11", NULL, NULL);
}
return rb_convert_to_integer(arg, base);
}
Creates a new Pathname object.
static VALUE
path_f_pathname(VALUE self, VALUE str)
{
return rb_class_new_instance(1, &str, rb_cPathname);
}
Returns x/y;
Rational(1, 2) #=> (1/2) Rational('1/2') #=> (1/2) Rational(nil) #=> TypeError Rational(1, nil) #=> TypeError
Syntax of string form:
string form = extra spaces , rational , extra spaces ;
rational = [ sign ] , unsigned rational ;
unsigned rational = numerator | numerator , "/" , denominator ;
numerator = integer part | fractional part | integer part , fractional part ;
denominator = digits ;
integer part = digits ;
fractional part = "." , digits , [ ( "e" | "E" ) , [ sign ] , digits ] ;
sign = "-" | "+" ;
digits = digit , { digit | "_" , digit } ;
digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
extra spaces = ? \s* ? ;
See String#to_r.
static VALUE
nurat_f_rational(int argc, VALUE *argv, VALUE klass)
{
return rb_funcall2(rb_cRational, id_convert, argc, argv);
}
Returns arg as an String.
First tries to call its to_str method, then its
to_s method.
String(self) #=> "main" String(self.class) #=> "Object" String(123456) #=> "123456"
static VALUE
rb_f_string(VALUE obj, VALUE arg)
{
return rb_String(arg);
}
static VALUE
rb_f_callee_name(void)
{
ID fname = rb_frame_callee(); /* need *callee* ID */
if (fname) {
return ID2SYM(fname);
}
else {
return Qnil;
}
}
Returns the canonicalized absolute path of the directory of the file from
which this method is called. It means symlinks in the path is resolved. If
__FILE__ is nil, it returns nil. The
return value equals to File.dirname(File.realpath(__FILE__)).
static VALUE
f_current_dirname(void)
{
VALUE base = rb_current_realfilepath();
if (NIL_P(base)) {
return Qnil;
}
base = rb_file_dirname(base);
return base;
}
Returns the name of the current method as a Symbol. If called outside of a method, it returns
nil.
static VALUE
rb_f_method_name(void)
{
ID fname = rb_frame_caller(); /* need *caller* ID */
if (fname) {
return ID2SYM(fname);
}
else {
return Qnil;
}
}
Returns the standard output of running cmd in a subshell. The
built-in syntax %x{...} uses this method. Sets $?
to the process status.
%x`date` #=> "Wed Apr 9 08:56:30 CDT 2003\n" %x`ls testdir`.split[1] #=> "main.rb" %x`echo oops && exit 99` #=> "oops\n" $?.exitstatus #=> 99
static VALUE
rb_f_backquote(VALUE obj, VALUE str)
{
volatile VALUE port;
VALUE result;
rb_io_t *fptr;
SafeStringValue(str);
rb_last_status_clear();
port = pipe_open_s(str, "r", FMODE_READABLE|DEFAULT_TEXTMODE, NULL);
if (NIL_P(port)) return rb_str_new(0,0);
GetOpenFile(port, fptr);
result = read_all(fptr, remain_size(fptr), Qnil);
rb_io_close(port);
return result;
}
Terminate execution immediately, effectively by calling
Kernel.exit(false). If msg is given, it is written to
STDERR prior to terminating.
VALUE
rb_f_abort(int argc, VALUE *argv)
{
rb_secure(4);
if (argc == 0) {
if (!NIL_P(GET_THREAD()->errinfo)) {
ruby_error_print();
}
rb_exit(EXIT_FAILURE);
}
else {
VALUE args[2];
rb_scan_args(argc, argv, "1", &args[1]);
StringValue(argv[0]);
rb_io_puts(argc, argv, rb_stderr);
args[0] = INT2NUM(EXIT_FAILURE);
rb_exc_raise(rb_class_new_instance(2, args, rb_eSystemExit));
}
UNREACHABLE;
}
Converts block to a Proc object (and therefore binds
it at the point of call) and registers it for execution when the program
exits. If multiple handlers are registered, they are executed in reverse
order of registration.
def do_at_exit(str1) at_exit { print str1 } end at_exit { puts "cruel world" } do_at_exit("goodbye ") exit
produces:
goodbye cruel world
static VALUE
rb_f_at_exit(void)
{
VALUE proc;
if (!rb_block_given_p()) {
rb_raise(rb_eArgError, "called without a block");
}
proc = rb_block_proc();
rb_set_end_proc(rb_call_end_proc, proc);
return proc;
}
Registers filename to be loaded (using
Kernel::require) the first time that module (which
may be a String or a symbol) is accessed.
autoload(:MyModule, "/usr/local/lib/modules/my_module.rb")
static VALUE
rb_f_autoload(VALUE obj, VALUE sym, VALUE file)
{
VALUE klass = rb_class_real(rb_vm_cbase());
if (NIL_P(klass)) {
rb_raise(rb_eTypeError, "Can not set autoload on singleton class");
}
return rb_mod_autoload(klass, sym, file);
}
Returns filename to be loaded if name is registered as
autoload.
autoload(:B, "b") autoload?(:B) #=> "b"
static VALUE
rb_f_autoload_p(VALUE obj, VALUE sym)
{
/* use rb_vm_cbase() as same as rb_f_autoload. */
VALUE klass = rb_vm_cbase();
if (NIL_P(klass)) {
return Qnil;
}
return rb_mod_autoload_p(klass, sym);
}
Returns a Binding object, describing the variable and method
bindings at the point of call. This object can be used when calling
eval to execute the evaluated command in this environment. See
also the description of class Binding.
def get_binding(param) return binding end b = get_binding("hello") eval("param", b) #=> "hello"
static VALUE
rb_f_binding(VALUE self)
{
return rb_binding_new();
}
Returns true if yield would execute a block in
the current context. The iterator? form is mildly deprecated.
def try if block_given? yield else "no block" end end try #=> "no block" try { "hello" } #=> "hello" try do "hello" end #=> "hello"
VALUE
rb_f_block_given_p(void)
{
rb_thread_t *th = GET_THREAD();
rb_control_frame_t *cfp = th->cfp;
cfp = vm_get_ruby_level_caller_cfp(th, RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp));
if (cfp != 0 && VM_CF_BLOCK_PTR(cfp)) {
return Qtrue;
}
else {
return Qfalse;
}
}
Generates a Continuation object, which it
passes to the associated block. You need to require
'continuation' before using this method. Performing a
cont.call will cause the callcc to return (as will falling
through the end of the block). The value returned by the callcc is the value of the block, or
the value passed to cont.call. See class Continuation for more details. Also see #throw for an alternative mechanism
for unwinding a call stack.
static VALUE
rb_callcc(VALUE self)
{
volatile int called;
volatile VALUE val = cont_capture(&called);
if (called) {
return val;
}
else {
return rb_yield(val);
}
}
Returns the current execution stack—an array containing strings in the form
file:line or file:line: in `method'.
The optional start parameter determines the number of initial stack entries to omit from the top of the stack.
A second optional length parameter can be used to limit how
many entries are returned from the stack.
Returns nil if start is greater than the size of
current execution stack.
Optionally you can pass a range, which will return an array containing the entries within the specified range.
def a(skip) caller(skip) end def b(skip) a(skip) end def c(skip) b(skip) end c(0) #=> ["prog:2:in `a'", "prog:5:in `b'", "prog:8:in `c'", "prog:10:in `<main>'"] c(1) #=> ["prog:5:in `b'", "prog:8:in `c'", "prog:11:in `<main>'"] c(2) #=> ["prog:8:in `c'", "prog:12:in `<main>'"] c(3) #=> ["prog:13:in `<main>'"] c(4) #=> [] c(5) #=> nil
static VALUE
rb_f_caller(int argc, VALUE *argv)
{
return vm_backtrace_to_ary(GET_THREAD(), argc, argv, 1, 1, 1);
}
Returns the current execution stack—an array containing backtrace location objects.
See Thread::Backtrace::Location for more information.
The optional start parameter determines the number of initial stack entries to omit from the top of the stack.
A second optional length parameter can be used to limit how
many entries are returned from the stack.
Returns nil if start is greater than the size of
current execution stack.
Optionally you can pass a range, which will return an array containing the entries within the specified range.
static VALUE
rb_f_caller_locations(int argc, VALUE *argv)
{
return vm_backtrace_to_ary(GET_THREAD(), argc, argv, 1, 1, 0);
}
catch executes its block. If a throw is executed,
Ruby searches up its stack for a catch block with a tag
corresponding to the throw's tag. If found, that
block is terminated, and catch returns the value given to
throw. If throw is not called, the block
terminates normally, and the value of catch is the value of
the last expression evaluated. catch expressions may be
nested, and the throw call need not be in lexical scope.
def routine(n) puts n throw :done if n <= 0 routine(n-1) end catch(:done) { routine(3) }
produces:
3 2 1 0
when arg is given, catch yields it as is, or when no
arg is given, catch assigns a new unique object to
throw. this is useful for nested catch.
arg can be an arbitrary object, not only Symbol.
static VALUE
rb_f_catch(int argc, VALUE *argv)
{
VALUE tag;
if (argc == 0) {
tag = rb_obj_alloc(rb_cObject);
}
else {
rb_scan_args(argc, argv, "01", &tag);
}
return rb_catch_obj(tag, catch_i, 0);
}
Equivalent to $_ = $_.chomp(string). See
String#chomp. Available only when -p/-n command line option
specified.
static VALUE
rb_f_chomp(int argc, VALUE *argv)
{
VALUE str = rb_funcall_passing_block(uscore_get(), rb_intern("chomp"), argc, argv);
rb_lastline_set(str);
return str;
}
Equivalent to ($_.dup).chop!, except nil is never
returned. See String#chop!. Available only when -p/-n command
line option specified.
static VALUE
rb_f_chop(void)
{
VALUE str = rb_funcall_passing_block(uscore_get(), rb_intern("chop"), 0, 0);
rb_lastline_set(str);
return str;
}
Evaluates the Ruby expression(s) in string. If binding is
given, which must be a Binding object, the evaluation is
performed in its context. If the optional filename and
lineno parameters are present, they will be used when reporting
syntax errors.
def get_binding(str) return binding end str = "hello" eval "str + ' Fred'" #=> "hello Fred" eval "str + ' Fred'", get_binding("bye") #=> "bye Fred"
VALUE
rb_f_eval(int argc, VALUE *argv, VALUE self)
{
VALUE src, scope, vfile, vline;
VALUE file = Qundef;
int line = 1;
rb_scan_args(argc, argv, "13", &src, &scope, &vfile, &vline);
if (rb_safe_level() >= 4) {
StringValue(src);
if (!NIL_P(scope) && !OBJ_TAINTED(scope)) {
rb_raise(rb_eSecurityError,
"Insecure: can't modify trusted binding");
}
}
else {
SafeStringValue(src);
}
if (argc >= 3) {
StringValue(vfile);
}
if (argc >= 4) {
line = NUM2INT(vline);
}
if (!NIL_P(vfile))
file = vfile;
return eval_string(self, src, scope, file, line);
}
Replaces the current process by running the given external command. command… is one of following forms.
commandline : command 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)
If single string is given as the command, it is taken as a command line that is subject to shell expansion before being executed.
The standard shell means always "/bin/sh" on
Unix-like systems, ENV["RUBYSHELL"] or
ENV["COMSPEC"] on Windows NT series, and similar.
If two or more string given, the first is taken as a command
name and the rest are passed as parameters to command with no shell
expansion.
If a two-element array at the beginning of the command, the first element
is the command to be executed, and the second argument is used as the
argv[0] value, which may show up in process listings.
In order to execute the command, one of the exec(2) system
calls is used, so the running command may inherit some of the environment
of the original program (including open file descriptors). This behavior is
modified by env and options. See spawn for details.
Raises SystemCallError if the command
couldn't execute (typically Errno::ENOENT when it was not
found).
This method modifies process attributes according to options
(details described in spawn) before exec(2)
system call. The modified attributes may be retained when
exec(2) system call fails. For example, hard resource limits
is not restorable. If it is not acceptable, consider to create a child
process using spawn or system.
exec "echo *" # echoes list of files in current directory # never get here exec "echo", "*" # echoes an asterisk # never get here
VALUE
rb_f_exec(int argc, VALUE *argv)
{
VALUE execarg_obj, fail_str;
struct rb_execarg *eargp;
#define CHILD_ERRMSG_BUFLEN 80
char errmsg[CHILD_ERRMSG_BUFLEN] = { '\0' };
execarg_obj = rb_execarg_new(argc, argv, TRUE);
eargp = rb_execarg_get(execarg_obj);
rb_execarg_fixup(execarg_obj);
fail_str = eargp->use_shell ? eargp->invoke.sh.shell_script : eargp->invoke.cmd.command_name;
#if defined(__APPLE__) || defined(__HAIKU__)
rb_exec_without_timer_thread(eargp, errmsg, sizeof(errmsg));
#else
rb_exec_async_signal_safe(eargp, errmsg, sizeof(errmsg));
#endif
RB_GC_GUARD(execarg_obj);
if (errmsg[0])
rb_sys_fail(errmsg);
rb_sys_fail_str(fail_str);
return Qnil; /* dummy */
}
Initiates the termination of the Ruby script by raising the
SystemExit exception. This exception may be caught. The
optional parameter is used to return a status code to the invoking
environment. true and FALSE of status
means success and failure respectively. The interpretation of other
integer values are system dependent.
begin exit puts "never get here" rescue SystemExit puts "rescued a SystemExit exception" end puts "after begin block"
produces:
rescued a SystemExit exception after begin block
Just prior to termination, Ruby executes any at_exit functions
(see Kernel::at_exit) and runs any object finalizers (see ObjectSpace.define_finalizer).
at_exit { puts "at_exit function" } ObjectSpace.define_finalizer("string", proc { puts "in finalizer" }) exit
produces:
at_exit function in finalizer
VALUE
rb_f_exit(int argc, VALUE *argv)
{
VALUE status;
int istatus;
rb_secure(4);
if (argc > 0 && rb_scan_args(argc, argv, "01", &status) == 1) {
istatus = exit_status_code(status);
}
else {
istatus = EXIT_SUCCESS;
}
rb_exit(istatus);
UNREACHABLE;
}
Exits the process immediately. No exit handlers are run. status is returned to the underlying system as the exit status.
Process.exit!(true)
static VALUE
rb_f_exit_bang(int argc, VALUE *argv, VALUE obj)
{
VALUE status;
int istatus;
rb_secure(4);
if (argc > 0 && rb_scan_args(argc, argv, "01", &status) == 1) {
istatus = exit_status_code(status);
}
else {
istatus = EXIT_FAILURE;
}
_exit(istatus);
UNREACHABLE;
}
With no arguments, raises the exception in $! or raises a
RuntimeError if $! is nil. With a
single String argument, raises a RuntimeError
with the string as a message. Otherwise, the first parameter should be the
name of an Exception class (or an object that returns an
Exception object when sent an exception message).
The optional second parameter sets the message associated with the
exception, and the third parameter is an array of callback information.
Exceptions are caught by the rescue clause of
begin...end blocks.
raise "Failed to create socket" raise ArgumentError, "No parameters", caller
static VALUE
rb_f_raise(int argc, VALUE *argv)
{
VALUE err;
if (argc == 0) {
err = get_errinfo();
if (!NIL_P(err)) {
argc = 1;
argv = &err;
}
}
rb_raise_jump(rb_make_exception(argc, argv));
UNREACHABLE;
}
Creates a subprocess. If a block is specified, that block is run in the
subprocess, and the subprocess terminates with a status of zero. Otherwise,
the fork call returns twice, once in the parent, returning the
process ID of the child, and once in the child, returning nil. The
child process can exit using Kernel.exit! to avoid running any
at_exit functions. The parent process should use
Process.wait to collect the termination statuses of its
children or use Process.detach to register disinterest in
their status; otherwise, the operating system may accumulate zombie
processes.
The thread calling fork is the only thread in the created child process. fork doesn't copy other threads.
If fork is not usable, Process.respond_to?(:fork) returns false.
static VALUE
rb_f_fork(VALUE obj)
{
rb_pid_t pid;
rb_secure(2);
switch (pid = rb_fork_ruby(NULL)) {
case 0:
rb_thread_atfork();
if (rb_block_given_p()) {
int status;
rb_protect(rb_yield, Qundef, &status);
ruby_stop(status);
}
return Qnil;
case -1:
rb_sys_fail("fork(2)");
return Qnil;
default:
return PIDT2NUM(pid);
}
}
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 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"
VALUE
rb_f_sprintf(int argc, const VALUE *argv)
{
return rb_str_format(argc - 1, argv + 1, GETNTHARG(0));
}
Returns (and assigns to $_) the next line from the list of
files in ARGV (or $*), or from standard input if
no files are present on the command line. Returns nil at end
of file. The optional argument specifies the record separator. The
separator is included with the contents of each record. A separator of
nil reads the entire contents, and a zero-length separator
reads the input one paragraph at a time, where paragraphs are divided by
two consecutive newlines. If the first argument is an integer, or optional
second argument is given, the returning string would not be longer than the
given value in bytes. If multiple filenames are present in
ARGV, +gets(nil)+ will read the contents one file at a time.
ARGV << "testfile" print while gets
produces:
This is line one This is line two This is line three And so on...
The style of programming using $_ as an implicit parameter is
gradually losing favor in the Ruby community.
static VALUE
rb_f_gets(int argc, VALUE *argv, VALUE recv)
{
if (recv == argf) {
return argf_gets(argc, argv, argf);
}
return rb_funcall2(argf, idGets, argc, argv);
}
Returns an array of the names of global variables.
global_variables.grep /std/ #=> [:$stdin, :$stdout, :$stderr]
VALUE
rb_f_global_variables(void)
{
VALUE ary = rb_ary_new();
char buf[2];
int i;
st_foreach_safe(rb_global_tbl, gvar_i, ary);
buf[0] = '$';
for (i = 1; i <= 9; ++i) {
buf[1] = (char)(i + '0');
rb_ary_push(ary, ID2SYM(rb_intern2(buf, 2)));
}
return ary;
}
Equivalent to $_.gsub..., except that $_ receives
the modified result. Available only when -p/-n command line option
specified.
static VALUE
rb_f_gsub(int argc, VALUE *argv)
{
VALUE str = rb_funcall_passing_block(uscore_get(), rb_intern("gsub"), argc, argv);
rb_lastline_set(str);
return str;
}
Returns true if yield would execute a block in
the current context. The iterator? form is mildly deprecated.
def try if block_given? yield else "no block" end end try #=> "no block" try { "hello" } #=> "hello" try do "hello" end #=> "hello"
VALUE
rb_f_block_given_p(void)
{
rb_thread_t *th = GET_THREAD();
rb_control_frame_t *cfp = th->cfp;
cfp = vm_get_ruby_level_caller_cfp(th, RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp));
if (cfp != 0 && VM_CF_BLOCK_PTR(cfp)) {
return Qtrue;
}
else {
return Qfalse;
}
}
Equivalent to Proc.new, except the resulting Proc objects check the number of parameters passed
when called.
VALUE
rb_block_lambda(void)
{
return proc_new(rb_cProc, TRUE);
}
Loads and executes the Ruby program in the file filename. If the
filename does not resolve to an absolute path, the file is searched for in
the library directories listed in $:. If the optional
wrap parameter is true, the loaded script will be
executed under an anonymous module, protecting the calling program's
global namespace. In no circumstance will any local variables in the loaded
file be propagated to the loading environment.
static VALUE
rb_f_load(int argc, VALUE *argv)
{
VALUE fname, wrap, path;
rb_scan_args(argc, argv, "11", &fname, &wrap);
if (RUBY_DTRACE_LOAD_ENTRY_ENABLED()) {
RUBY_DTRACE_LOAD_ENTRY(StringValuePtr(fname),
rb_sourcefile(),
rb_sourceline());
}
path = rb_find_file(FilePathValue(fname));
if (!path) {
if (!rb_file_load_ok(RSTRING_PTR(fname)))
load_failed(fname);
path = fname;
}
rb_load_internal(path, RTEST(wrap));
if (RUBY_DTRACE_LOAD_RETURN_ENABLED()) {
RUBY_DTRACE_LOAD_RETURN(StringValuePtr(fname),
rb_sourcefile(),
rb_sourceline());
}
return Qtrue;
}
Returns the names of the current local variables.
fred = 1 for i in 1..10 # ... end local_variables #=> [:fred, :i]
static VALUE
rb_f_local_variables(void)
{
VALUE ary = rb_ary_new();
rb_thread_t *th = GET_THREAD();
rb_control_frame_t *cfp =
vm_get_ruby_level_caller_cfp(th, RUBY_VM_PREVIOUS_CONTROL_FRAME(th->cfp));
int i;
while (cfp) {
if (cfp->iseq) {
for (i = 0; i < cfp->iseq->local_table_size; i++) {
ID lid = cfp->iseq->local_table[i];
if (lid) {
const char *vname = rb_id2name(lid);
/* should skip temporary variable */
if (vname) {
rb_ary_push(ary, ID2SYM(lid));
}
}
}
}
if (!VM_EP_LEP_P(cfp->ep)) {
/* block */
VALUE *ep = VM_CF_PREV_EP(cfp);
if (vm_collect_local_variables_in_heap(th, ep, ary)) {
break;
}
else {
while (cfp->ep != ep) {
cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
}
}
}
else {
break;
}
}
return ary;
}
Repeatedly executes the block.
If no block is given, an enumerator is returned instead.
loop do print "Input: " line = gets break if !line or line =~ /^qQ/ # ... end
StopIteration raised in the block breaks the loop.
static VALUE
rb_f_loop(VALUE self)
{
RETURN_SIZED_ENUMERATOR(self, 0, 0, rb_f_loop_size);
rb_rescue2(loop_i, (VALUE)0, 0, 0, rb_eStopIteration, (VALUE)0);
return Qnil; /* dummy */
}
For each object, directly writes obj.inspect followed
by a newline to the program's standard output.
S = Struct.new(:name, :state) s = S['dave', 'TX'] p s
produces:
#<S name="dave", state="TX">
static VALUE
rb_f_p(int argc, VALUE *argv, VALUE self)
{
struct rb_f_p_arg arg;
arg.argc = argc;
arg.argv = argv;
return rb_uninterruptible(rb_f_p_internal, (VALUE)&arg);
}
returns a pretty printed object as a string.
# File lib/pp.rb, line 5 def pretty_inspect PP.pp(self, '') end
Prints each object in turn to $stdout. If the output field
separator ($,) is not nil, its contents will
appear between each field. If the output record separator ($\)
is not nil, it will be appended to the output. If no arguments
are given, prints $_. Objects that aren't strings will be
converted by calling their to_s method.
print "cat", [1,2,3], 99, "\n" $, = ", " $\ = "\n" print "cat", [1,2,3], 99
produces:
cat12399 cat, 1, 2, 3, 99
static VALUE
rb_f_print(int argc, VALUE *argv)
{
rb_io_print(argc, argv, rb_stdout);
return Qnil;
}
Equivalent to:
io.write(sprintf(string, obj, ...)
or
$stdout.write(sprintf(string, obj, ...)
static VALUE
rb_f_printf(int argc, VALUE *argv)
{
VALUE out;
if (argc == 0) return Qnil;
if (RB_TYPE_P(argv[0], T_STRING)) {
out = rb_stdout;
}
else {
out = argv[0];
argv++;
argc--;
}
rb_io_write(out, rb_f_sprintf(argc, argv));
return Qnil;
}
Equivalent to Proc.new.
VALUE
rb_block_proc(void)
{
return proc_new(rb_cProc, FALSE);
}
Equivalent to: $stdout.putc(int)
Refer to the documentation for IO#putc for important information regarding multi-byte characters.
static VALUE
rb_f_putc(VALUE recv, VALUE ch)
{
if (recv == rb_stdout) {
return rb_io_putc(recv, ch);
}
return rb_funcall2(rb_stdout, rb_intern("putc"), 1, &ch);
}
Equivalent to
$stdout.puts(obj, ...)
static VALUE
rb_f_puts(int argc, VALUE *argv, VALUE recv)
{
if (recv == rb_stdout) {
return rb_io_puts(argc, argv, recv);
}
return rb_funcall2(rb_stdout, rb_intern("puts"), argc, argv);
}
With no arguments, raises the exception in $! or raises a
RuntimeError if $! is nil. With a
single String argument, raises a RuntimeError
with the string as a message. Otherwise, the first parameter should be the
name of an Exception class (or an object that returns an
Exception object when sent an exception message).
The optional second parameter sets the message associated with the
exception, and the third parameter is an array of callback information.
Exceptions are caught by the rescue clause of
begin...end blocks.
raise "Failed to create socket" raise ArgumentError, "No parameters", caller
static VALUE
rb_f_raise(int argc, VALUE *argv)
{
VALUE err;
if (argc == 0) {
err = get_errinfo();
if (!NIL_P(err)) {
argc = 1;
argv = &err;
}
}
rb_raise_jump(rb_make_exception(argc, argv));
UNREACHABLE;
}
If called without an argument, or if max.to_i.abs == 0, rand
returns a pseudo-random floating point number between 0.0 and 1.0,
including 0.0 and excluding 1.0.
rand #=> 0.2725926052826416
When max.abs is greater than or equal to 1, rand
returns a pseudo-random integer greater than or equal to 0 and less than
max.to_i.abs.
rand(100) #=> 12
When max is a Range,
rand returns a random number where range.member?(number) ==
true.
Negative or floating point values for max are allowed, but may
give surprising results.
rand(-100) # => 87 rand(-0.5) # => 0.8130921818028143 rand(1.9) # equivalent to rand(1), which is always 0
#srand may be used to ensure that sequences of random numbers are reproducible between different runs of a program.
See also Random#rand.
static VALUE
rb_f_rand(int argc, VALUE *argv, VALUE obj)
{
VALUE v, vmax, r;
struct MT *mt = default_mt();
if (argc == 0) goto zero_arg;
rb_scan_args(argc, argv, "01", &vmax);
if (NIL_P(vmax)) goto zero_arg;
if ((v = rand_range(mt, vmax)) != Qfalse) {
return v;
}
vmax = rb_to_int(vmax);
if (vmax == INT2FIX(0) || NIL_P(r = rand_int(mt, vmax, 0))) {
zero_arg:
return DBL2NUM(genrand_real(mt));
}
return r;
}
Equivalent to Kernel::gets, except readline
raises EOFError at end of file.
static VALUE
rb_f_readline(int argc, VALUE *argv, VALUE recv)
{
if (recv == argf) {
return argf_readline(argc, argv, argf);
}
return rb_funcall2(argf, rb_intern("readline"), argc, argv);
}
Returns an array containing the lines returned by calling
Kernel.gets(sep) until the end of file.
static VALUE
rb_f_readlines(int argc, VALUE *argv, VALUE recv)
{
if (recv == argf) {
return argf_readlines(argc, argv, argf);
}
return rb_funcall2(argf, rb_intern("readlines"), argc, argv);
}
Ruby tries to load the library named string relative to the
requiring file's path. If the file's path cannot be determined a
LoadError is raised. If a file is loaded
true is returned and false otherwise.
VALUE
rb_f_require_relative(VALUE obj, VALUE fname)
{
VALUE base = rb_current_realfilepath();
if (NIL_P(base)) {
rb_loaderror("cannot infer basepath");
}
base = rb_file_dirname(base);
return rb_require_safe(rb_file_absolute_path(fname, base), rb_safe_level());
}
Calls select(2) system call. It monitors given arrays of IO
objects, waits one or more of IO objects ready for reading,
are ready for writing, and have pending exceptions respectably, and returns
an array that contains arrays of those IO objects.
It will return nil if optional timeout value is given
and no IO object is ready in timeout seconds.
Parameters¶ ↑
- read_array
-
an array of
IOobjects that wait until ready for read - write_array
-
an array of
IOobjects that wait until ready for write - error_array
-
an array of
IOobjects that wait for exceptions - timeout
-
a numeric value in second
Example¶ ↑
rp, wp = IO.pipe mesg = "ping " 100.times { rs, ws, = IO.select([rp], [wp]) if r = rs[0] ret = r.read(5) print ret case ret when /ping/ mesg = "pong\n" when /pong/ mesg = "ping " end end if w = ws[0] w.write(mesg) end }
produces:
ping pong ping pong ping pong (snipped) ping
static VALUE
rb_f_select(int argc, VALUE *argv, VALUE obj)
{
VALUE timeout;
struct select_args args;
struct timeval timerec;
int i;
rb_scan_args(argc, argv, "13", &args.read, &args.write, &args.except, &timeout);
if (NIL_P(timeout)) {
args.timeout = 0;
}
else {
timerec = rb_time_interval(timeout);
args.timeout = &timerec;
}
for (i = 0; i < numberof(args.fdsets); ++i)
rb_fd_init(&args.fdsets[i]);
return rb_ensure(select_call, (VALUE)&args, select_end, (VALUE)&args);
}
Establishes proc as the handler for tracing, or disables tracing
if the parameter is nil.
proc takes up to six parameters:
-
an event name
-
a filename
-
a line number
-
an object id
-
a binding
-
the name of a class
proc is invoked whenever an event occurs.
Events are:
c-call-
call a C-language routine
c-return-
return from a C-language routine
call-
call a Ruby method
class-
start a class or module definition),
end-
finish a class or module definition),
line-
execute code on a new line
raise-
raise an exception
return-
return from a Ruby method
Tracing is disabled within the context of proc.
class Test
def test
a = 1
b = 2
end
end
set_trace_func proc { |event, file, line, id, binding, classname|
printf "%8s %s:%-2d %10s %8s\n", event, file, line, id, classname
}
t = Test.new
t.test
line prog.rb:11 false
c-call prog.rb:11 new Class
c-call prog.rb:11 initialize Object
c-return prog.rb:11 initialize Object
c-return prog.rb:11 new Class
line prog.rb:12 false
call prog.rb:2 test Test
line prog.rb:3 test Test
line prog.rb:4 test Test
return prog.rb:4 test Test
static VALUE
set_trace_func(VALUE obj, VALUE trace)
{
rb_secure(4);
rb_remove_event_hook(call_trace_func);
if (NIL_P(trace)) {
return Qnil;
}
if (!rb_obj_is_proc(trace)) {
rb_raise(rb_eTypeError, "trace_func needs to be Proc");
}
rb_add_event_hook(call_trace_func, RUBY_EVENT_ALL, trace);
return trace;
}
Suspends the current thread for duration seconds (which may be any
number, including a Float with fractional seconds). Returns
the actual number of seconds slept (rounded), which may be less than that
asked for if another thread calls Thread#run. Called without
an argument, sleep() will sleep forever.
Time.new #=> 2008-03-08 19:56:19 +0900 sleep 1.2 #=> 1 Time.new #=> 2008-03-08 19:56:20 +0900 sleep 1.9 #=> 2 Time.new #=> 2008-03-08 19:56:22 +0900
static VALUE
rb_f_sleep(int argc, VALUE *argv)
{
time_t beg, end;
beg = time(0);
if (argc == 0) {
rb_thread_sleep_forever();
}
else {
rb_check_arity(argc, 0, 1);
rb_thread_wait_for(rb_time_interval(argv[0]));
}
end = time(0) - beg;
return INT2FIX(end);
}
spawn executes specified command and return its pid.
This method doesn't wait for end of the command. 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
command...:
commandline : command 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)
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 to 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 => true : don't inherit
current directory:
:chdir => str
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 or positive integer.
true and zero means the process should be a process leader of a new process
group. Other values specifies a process group to be belongs.
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, a fixnum, 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, 3=>"/dev/null") # read mode
For stdout and stderr, 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 true 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.
static VALUE
rb_f_spawn(int argc, VALUE *argv)
{
rb_pid_t pid;
char errmsg[CHILD_ERRMSG_BUFLEN] = { '\0' };
VALUE execarg_obj, fail_str;
struct rb_execarg *eargp;
execarg_obj = rb_execarg_new(argc, argv, TRUE);
eargp = rb_execarg_get(execarg_obj);
rb_execarg_fixup(execarg_obj);
fail_str = eargp->use_shell ? eargp->invoke.sh.shell_script : eargp->invoke.cmd.command_name;
pid = rb_spawn_process(eargp, errmsg, sizeof(errmsg));
RB_GC_GUARD(execarg_obj);
if (pid == -1) {
const char *prog = errmsg;
if (!prog[0]) {
rb_sys_fail_str(fail_str);
}
rb_sys_fail(prog);
}
#if defined(HAVE_FORK) || defined(HAVE_SPAWNV)
return PIDT2NUM(pid);
#else
return Qnil;
#endif
}
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 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"
VALUE
rb_f_sprintf(int argc, const VALUE *argv)
{
return rb_str_format(argc - 1, argv + 1, GETNTHARG(0));
}
Seeds the system pseudo-random number generator, Random::DEFAULT, with
number. The previous seed value is returned.
If number is omitted, seeds the generator using a source of
entropy provided by the operating system, if available (/dev/urandom on
Unix systems or the RSA cryptographic provider on Windows), which is then
combined with the time, the process id, and a sequence number.
srand may be used to ensure repeatable sequences of pseudo-random numbers between different runs of the program. By setting the seed to a known value, programs can be made deterministic during testing.
srand 1234 # => 268519324636777531569100071560086917274 [ rand, rand ] # => [0.1915194503788923, 0.6221087710398319] [ rand(10), rand(1000) ] # => [4, 664] srand 1234 # => 1234 [ rand, rand ] # => [0.1915194503788923, 0.6221087710398319]
static VALUE
rb_f_srand(int argc, VALUE *argv, VALUE obj)
{
VALUE seed, old;
rb_random_t *r = &default_rand;
rb_secure(4);
if (argc == 0) {
seed = random_seed();
}
else {
rb_scan_args(argc, argv, "01", &seed);
}
old = r->seed;
r->seed = rand_init(&r->mt, seed);
return old;
}
Equivalent to $_.sub(args), except that
$_ will be updated if substitution occurs. Available only when
-p/-n command line option specified.
static VALUE
rb_f_sub(int argc, VALUE *argv)
{
VALUE str = rb_funcall_passing_block(uscore_get(), rb_intern("sub"), argc, argv);
rb_lastline_set(str);
return str;
}
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 same as a pointer. Up to nine parameters may be passed (14 on the Atari-ST). The function identified by _num_ is system dependent. On some Unix systems, the numbers may be obtained from a header file called <code>syscall.h</code>. syscall 4, 1, "hello\n", 6 # '4' is write(2) on our box <em>produces:</em> hello Calling +syscall+ on a platform which does not have any way to an arbitrary system function just fails with NotImplementedError.
- Note
-
syscallis essentially unsafe and unportable. Feel free to shoot your foot. DL (Fiddle) library is preferred for safer and a bit more portable programming.
static VALUE
rb_f_syscall(int argc, VALUE *argv)
{
#ifdef atarist
VALUE arg[13]; /* yes, we really need that many ! */
#else
VALUE arg[8];
#endif
#if SIZEOF_VOIDP == 8 && defined(HAVE___SYSCALL) && SIZEOF_INT != 8 /* mainly *BSD */
# define SYSCALL __syscall
# define NUM2SYSCALLID(x) NUM2LONG(x)
# define RETVAL2NUM(x) LONG2NUM(x)
# if SIZEOF_LONG == 8
long num, retval = -1;
# elif SIZEOF_LONG_LONG == 8
long long num, retval = -1;
# else
# error ---->> it is asserted that __syscall takes the first argument and returns retval in 64bit signed integer. <<----
# endif
#elif defined(__linux__)
# define SYSCALL syscall
# define NUM2SYSCALLID(x) NUM2LONG(x)
# define RETVAL2NUM(x) LONG2NUM(x)
/*
* Linux man page says, syscall(2) function prototype is below.
*
* int syscall(int number, ...);
*
* But, it's incorrect. Actual one takes and returned long. (see unistd.h)
*/
long num, retval = -1;
#else
# define SYSCALL syscall
# define NUM2SYSCALLID(x) NUM2INT(x)
# define RETVAL2NUM(x) INT2NUM(x)
int num, retval = -1;
#endif
int i;
if (RTEST(ruby_verbose)) {
rb_warning("We plan to remove a syscall function at future release. DL(Fiddle) provides safer alternative.");
}
rb_secure(2);
if (argc == 0)
rb_raise(rb_eArgError, "too few arguments for syscall");
if (argc > numberof(arg))
rb_raise(rb_eArgError, "too many arguments for syscall");
num = NUM2SYSCALLID(argv[0]); ++argv;
for (i = argc - 1; i--; ) {
VALUE v = rb_check_string_type(argv[i]);
if (!NIL_P(v)) {
SafeStringValue(v);
rb_str_modify(v);
arg[i] = (VALUE)StringValueCStr(v);
}
else {
arg[i] = (VALUE)NUM2LONG(argv[i]);
}
}
switch (argc) {
case 1:
retval = SYSCALL(num);
break;
case 2:
retval = SYSCALL(num, arg[0]);
break;
case 3:
retval = SYSCALL(num, arg[0],arg[1]);
break;
case 4:
retval = SYSCALL(num, arg[0],arg[1],arg[2]);
break;
case 5:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3]);
break;
case 6:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4]);
break;
case 7:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5]);
break;
case 8:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6]);
break;
#ifdef atarist
case 9:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
arg[7]);
break;
case 10:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
arg[7], arg[8]);
break;
case 11:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
arg[7], arg[8], arg[9]);
break;
case 12:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
arg[7], arg[8], arg[9], arg[10]);
break;
case 13:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
arg[7], arg[8], arg[9], arg[10], arg[11]);
break;
case 14:
retval = SYSCALL(num, arg[0],arg[1],arg[2],arg[3],arg[4],arg[5],arg[6],
arg[7], arg[8], arg[9], arg[10], arg[11], arg[12]);
break;
#endif
}
if (retval == -1)
rb_sys_fail(0);
return RETVAL2NUM(retval);
#undef SYSCALL
#undef NUM2SYSCALLID
#undef RETVAL2NUM
}
Executes command… in a subshell. command… is one of following forms.
commandline : command 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 $?.
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 *
See Kernel.exec for the standard shell.
static VALUE
rb_f_system(int argc, VALUE *argv)
{
rb_pid_t pid;
int status;
#if defined(SIGCLD) && !defined(SIGCHLD)
# define SIGCHLD SIGCLD
#endif
#ifdef SIGCHLD
RETSIGTYPE (*chfunc)(int);
rb_last_status_clear();
chfunc = signal(SIGCHLD, SIG_DFL);
#endif
pid = rb_spawn_internal(argc, argv, NULL, 0);
#if defined(HAVE_FORK) || defined(HAVE_SPAWNV)
if (pid > 0) {
int ret, status;
ret = rb_waitpid(pid, &status, 0);
if (ret == (rb_pid_t)-1)
rb_sys_fail("Another thread waited the process started by system().");
}
#endif
#ifdef SIGCHLD
signal(SIGCHLD, chfunc);
#endif
if (pid < 0) {
return Qnil;
}
status = PST2INT(rb_last_status_get());
if (status == EXIT_SUCCESS) return Qtrue;
return Qfalse;
}
Uses the integer cmd to perform various tests on
file1 (first table below) or on file1 and
file2 (second table).
File tests on a single file:
Cmd Returns Meaning
"A" | Time | Last access time for file1
"b" | boolean | True if file1 is a block device
"c" | boolean | True if file1 is a character device
"C" | Time | Last change time for file1
"d" | boolean | True if file1 exists and is a directory
"e" | boolean | True if file1 exists
"f" | boolean | True if file1 exists and is a regular file
"g" | boolean | True if file1 has the \CF{setgid} bit
| | set (false under NT)
"G" | boolean | True if file1 exists and has a group
| | ownership equal to the caller's group
"k" | boolean | True if file1 exists and has the sticky bit set
"l" | boolean | True if file1 exists and is a symbolic link
"M" | Time | Last modification time for file1
"o" | boolean | True if file1 exists and is owned by
| | the caller's effective uid
"O" | boolean | True if file1 exists and is owned by
| | the caller's real uid
"p" | boolean | True if file1 exists and is a fifo
"r" | boolean | True if file1 is readable by the effective
| | uid/gid of the caller
"R" | boolean | True if file is readable by the real
| | uid/gid of the caller
"s" | int/nil | If file1 has nonzero size, return the size,
| | otherwise return nil
"S" | boolean | True if file1 exists and is a socket
"u" | boolean | True if file1 has the setuid bit set
"w" | boolean | True if file1 exists and is writable by
| | the effective uid/gid
"W" | boolean | True if file1 exists and is writable by
| | the real uid/gid
"x" | boolean | True if file1 exists and is executable by
| | the effective uid/gid
"X" | boolean | True if file1 exists and is executable by
| | the real uid/gid
"z" | boolean | True if file1 exists and has a zero length
Tests that take two files:
"-" | boolean | True if file1 and file2 are identical
"=" | boolean | True if the modification times of file1
| | and file2 are equal
"<" | boolean | True if the modification time of file1
| | is prior to that of file2
">" | boolean | True if the modification time of file1
| | is after that of file2
static VALUE
rb_f_test(int argc, VALUE *argv)
{
int cmd;
if (argc == 0) rb_check_arity(argc, 2, 3);
cmd = NUM2CHR(argv[0]);
if (cmd == 0) {
unknown:
/* unknown command */
if (ISPRINT(cmd)) {
rb_raise(rb_eArgError, "unknown command '%s%c'", cmd == '\'' || cmd == '\\' ? "\\" : "", cmd);
}
else {
rb_raise(rb_eArgError, "unknown command \"\\x%02X\"", cmd);
}
}
if (strchr("bcdefgGkloOprRsSuwWxXz", cmd)) {
CHECK(1);
switch (cmd) {
case 'b':
return rb_file_blockdev_p(0, argv[1]);
case 'c':
return rb_file_chardev_p(0, argv[1]);
case 'd':
return rb_file_directory_p(0, argv[1]);
case 'a':
case 'e':
return rb_file_exist_p(0, argv[1]);
case 'f':
return rb_file_file_p(0, argv[1]);
case 'g':
return rb_file_sgid_p(0, argv[1]);
case 'G':
return rb_file_grpowned_p(0, argv[1]);
case 'k':
return rb_file_sticky_p(0, argv[1]);
case 'l':
return rb_file_symlink_p(0, argv[1]);
case 'o':
return rb_file_owned_p(0, argv[1]);
case 'O':
return rb_file_rowned_p(0, argv[1]);
case 'p':
return rb_file_pipe_p(0, argv[1]);
case 'r':
return rb_file_readable_p(0, argv[1]);
case 'R':
return rb_file_readable_real_p(0, argv[1]);
case 's':
return rb_file_size_p(0, argv[1]);
case 'S':
return rb_file_socket_p(0, argv[1]);
case 'u':
return rb_file_suid_p(0, argv[1]);
case 'w':
return rb_file_writable_p(0, argv[1]);
case 'W':
return rb_file_writable_real_p(0, argv[1]);
case 'x':
return rb_file_executable_p(0, argv[1]);
case 'X':
return rb_file_executable_real_p(0, argv[1]);
case 'z':
return rb_file_zero_p(0, argv[1]);
}
}
if (strchr("MAC", cmd)) {
struct stat st;
VALUE fname = argv[1];
CHECK(1);
if (rb_stat(fname, &st) == -1) {
FilePathValue(fname);
rb_sys_fail_path(fname);
}
switch (cmd) {
case 'A':
return stat_atime(&st);
case 'M':
return stat_mtime(&st);
case 'C':
return stat_ctime(&st);
}
}
if (cmd == '-') {
CHECK(2);
return rb_file_identical_p(0, argv[1], argv[2]);
}
if (strchr("=<>", cmd)) {
struct stat st1, st2;
CHECK(2);
if (rb_stat(argv[1], &st1) < 0) return Qfalse;
if (rb_stat(argv[2], &st2) < 0) return Qfalse;
switch (cmd) {
case '=':
if (st1.st_mtime == st2.st_mtime) return Qtrue;
return Qfalse;
case '>':
if (st1.st_mtime > st2.st_mtime) return Qtrue;
return Qfalse;
case '<':
if (st1.st_mtime < st2.st_mtime) return Qtrue;
return Qfalse;
}
}
goto unknown;
}
Transfers control to the end of the active catch block waiting
for tag. Raises ArgumentError 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.
static VALUE
rb_f_throw(int argc, VALUE *argv)
{
VALUE tag, value;
rb_scan_args(argc, argv, "11", &tag, &value);
rb_throw_obj(tag, value);
UNREACHABLE;
}
Controls tracing of assignments to global variables. The parameter +symbol_
identifies the variable (as either a string name or a symbol identifier).
cmd (which may be a string or a Proc object) or block
is executed whenever the variable is assigned. The block or
Proc object receives the variable's new value as a
parameter. Also see Kernel::untrace_var.
trace_var :$_, proc {|v| puts "$_ is now '#{v}'" } $_ = "hello" $_ = ' there'
produces:
$_ is now 'hello' $_ is now ' there'
VALUE
rb_f_trace_var(int argc, VALUE *argv)
{
VALUE var, cmd;
struct global_entry *entry;
struct trace_var *trace;
rb_secure(4);
if (rb_scan_args(argc, argv, "11", &var, &cmd) == 1) {
cmd = rb_block_proc();
}
if (NIL_P(cmd)) {
return rb_f_untrace_var(argc, argv);
}
entry = rb_global_entry(rb_to_id(var));
if (OBJ_TAINTED(cmd)) {
rb_raise(rb_eSecurityError, "Insecure: tainted variable trace");
}
trace = ALLOC(struct trace_var);
trace->next = entry->var->trace;
trace->func = rb_trace_eval;
trace->data = cmd;
trace->removed = 0;
entry->var->trace = trace;
return Qnil;
}
Specifies the handling of signals. The first parameter is a signal name (a string such as “SIGALRM'', “SIGUSR1'', and so on) or a signal number. The characters “SIG'' may be omitted from the signal name. The command or block specifies code to be run when the signal is raised. If the command is the string “IGNORE'' or “SIG_IGN'', the signal will be ignored. If the command is “DEFAULT'' or “SIG_DFL'', the Ruby's default handler will be invoked. If the command is “EXIT'', the script will be terminated by the signal. If the command is “SYSTEM_DEFAULT'', the operating system's default handler will be invoked. Otherwise, the given command or block will be run. The special signal name “EXIT'' or signal number zero will be invoked just prior to program termination. trap returns the previous handler for the given signal.
Signal.trap(0, proc { puts "Terminating: #{$$}" }) Signal.trap("CLD") { puts "Child died" } fork && Process.wait
produces:
Terminating: 27461 Child died Terminating: 27460
static VALUE
sig_trap(int argc, VALUE *argv)
{
int sig;
sighandler_t func;
VALUE cmd;
rb_secure(2);
rb_check_arity(argc, 1, 2);
sig = trap_signm(argv[0]);
if (reserved_signal_p(sig)) {
const char *name = signo2signm(sig);
if (name)
rb_raise(rb_eArgError, "can't trap reserved signal: SIG%s", name);
else
rb_raise(rb_eArgError, "can't trap reserved signal: %d", sig);
}
if (argc == 1) {
cmd = rb_block_proc();
func = sighandler;
}
else {
cmd = argv[1];
func = trap_handler(&cmd, sig);
}
if (OBJ_TAINTED(cmd)) {
rb_raise(rb_eSecurityError, "Insecure: tainted signal trap");
}
return trap(sig, func, cmd);
}
Removes tracing for the specified command on the given global variable and
returns nil. If no command is specified, removes all tracing
for that variable and returns an array containing the commands actually
removed.
VALUE
rb_f_untrace_var(int argc, VALUE *argv)
{
VALUE var, cmd;
ID id;
struct global_entry *entry;
struct trace_var *trace;
st_data_t data;
rb_secure(4);
rb_scan_args(argc, argv, "11", &var, &cmd);
id = rb_check_id(&var);
if (!id) {
rb_name_error_str(var, "undefined global variable %"PRIsVALUE"", QUOTE(var));
}
if (!st_lookup(rb_global_tbl, (st_data_t)id, &data)) {
rb_name_error(id, "undefined global variable %"PRIsVALUE"", QUOTE_ID(id));
}
trace = (entry = (struct global_entry *)data)->var->trace;
if (NIL_P(cmd)) {
VALUE ary = rb_ary_new();
while (trace) {
struct trace_var *next = trace->next;
rb_ary_push(ary, (VALUE)trace->data);
trace->removed = 1;
trace = next;
}
if (!entry->var->block_trace) remove_trace(entry->var);
return ary;
}
else {
while (trace) {
if (trace->data == cmd) {
trace->removed = 1;
if (!entry->var->block_trace) remove_trace(entry->var);
return rb_ary_new3(1, cmd);
}
trace = trace->next;
}
}
return Qnil;
}
Displays each of the given messages followed by a record separator on
STDERR unless warnings have been disabled (for example with the
-W0 flag).
warn("warning 1", "warning 2")
<em>produces:</em>
warning 1
warning 2
static VALUE
rb_warn_m(int argc, VALUE *argv, VALUE exc)
{
if (!NIL_P(ruby_verbose) && argc > 0) {
rb_io_puts(argc, argv, rb_stderr);
}
return Qnil;
}
Private Instance Methods
If object is string-like, parse the string and return the parsed result as a Ruby data structure. Otherwise, generate a JSON text from the Ruby data structure object and return it.
The opts argument is passed through to generate/parse respectively. See generate and parse for their documentation.
# File ext/json/lib/json/common.rb, line 470 def JSON(object, *args) if object.respond_to? :to_str JSON.parse(object.to_str, args.first) else JSON.generate(object, args.first) end end
Returns uri converted to a URI object.
# File lib/uri/common.rb, line 992 def URI(uri) if uri.is_a?(URI::Generic) uri elsif uri = String.try_convert(uri) URI.parse(uri) else raise ArgumentError, "bad argument (expected URI object or URI string)" end end
Use #gem to activate a specific
version of gem_name.
requirements is a list of version requirements that the
specified gem must match, most commonly “= example.version.number”. See Gem::Requirement for how to specify a
version requirement.
If you will be activating the latest version of a gem, there is no need to call #gem, #require will do the right thing for you.
#gem returns true if the gem was activated, otherwise false. If the gem could not be found, didn't match the version requirements, or a different version was already activated, an exception will be raised.
#gem should be called before any require statements (otherwise RubyGems may load a conflicting library version).
In older RubyGems versions, the environment variable GEM_SKIP could be used to skip activation of specified gems, for example to test out changes that haven't been installed yet. Now RubyGems defers to -I and the RUBYLIB environment variable to skip activation of a gem.
Example:
GEM_SKIP=libA:libB ruby -I../libA -I../libB ./mycode.rb
# File lib/rubygems/core_ext/kernel_gem.rb, line 32 def gem(gem_name, *requirements) # :doc: skip_list = (ENV['GEM_SKIP'] || "").split(/:/) raise Gem::LoadError, "skipping #{gem_name}" if skip_list.include? gem_name if gem_name.kind_of? Gem::Dependency unless Gem::Deprecate.skip warn "#{Gem.location_of_caller.join ':'}:Warning: Kernel.gem no longer " "accepts a Gem::Dependency object, please pass the name " "and requirements directly" end requirements = gem_name.requirement gem_name = gem_name.name end spec = Gem::Dependency.new(gem_name, *requirements).to_spec spec.activate if spec end
Outputs objs to STDOUT as JSON strings in the shortest form, that is in one line.
# File ext/json/lib/json/common.rb, line 448 def j(*objs) objs.each do |obj| puts JSON::generate(obj, :allow_nan => true, :max_nesting => false) end nil end
Ouputs objs to STDOUT as JSON strings in a pretty format, with indentation and over many lines.
# File ext/json/lib/json/common.rb, line 457 def jj(*objs) objs.each do |obj| puts JSON::pretty_generate(obj, :allow_nan => true, :max_nesting => false) end nil end
Creates an IO object connected to the given stream, file, or subprocess.
If path does not start with a pipe character (|),
treat it as the name of a file to open using the specified mode (defaulting
to “r”).
The mode is either a string or an integer. If it is an
integer, it must be bitwise-or of open(2) flags, such as File::RDWR or
File::EXCL. If it is a string, it is either “fmode”, “fmode:ext_enc”, or
“fmode:ext_enc:int_enc”.
See the documentation of IO.new for full
documentation of the mode string directives.
If a file is being created, its initial permissions may be set using the
perm parameter. See File.new and the open(2) and chmod(2) man
pages for a description of permissions.
If a block is specified, it will be invoked with the IO object as a parameter, and the IO will be automatically closed when the block terminates. The call returns the value of the block.
If path starts with a pipe character
("|"), a subprocess is created, connected to the
caller by a pair of pipes. The returned IO object
may be used to write to the standard input and read from the standard
output of this subprocess.
If the command following the pipe is a single minus sign
("|-"), Ruby forks, and this subprocess is connected
to the parent. If the command is not "-", the
subprocess runs the command.
When the subprocess is ruby (opened via "|-"), the
open call returns nil. If a block is associated
with the open call, that block will run twice — once in the parent and once
in the child.
The block parameter will be an IO object in the
parent and nil in the child. The parent's IO
object will be connected to the child's $stdin and $stdout. The
subprocess will be terminated at the end of the block.
Examples¶ ↑
Reading from “testfile”:
open("testfile") do |f| print f.gets end
Produces:
This is line one
Open a subprocess and read its output:
cmd = open("|date") print cmd.gets cmd.close
Produces:
Wed Apr 9 08:56:31 CDT 2003
Open a subprocess running the same Ruby program:
f = open("|-", "w+") if f == nil puts "in Child" exit else puts "Got: #{f.gets}" end
Produces:
Got: in Child
Open a subprocess using a block to receive the IO object:
open "|-" do |f| if f then # parent process puts "Got: #{f.gets}" else # child process puts "in Child" end end
Produces:
Got: in Child
static VALUE
rb_f_open(int argc, VALUE *argv)
{
ID to_open = 0;
int redirect = FALSE;
if (argc >= 1) {
CONST_ID(to_open, "to_open");
if (rb_respond_to(argv[0], to_open)) {
redirect = TRUE;
}
else {
VALUE tmp = argv[0];
FilePathValue(tmp);
if (NIL_P(tmp)) {
redirect = TRUE;
}
else {
VALUE cmd = check_pipe_command(tmp);
if (!NIL_P(cmd)) {
argv[0] = cmd;
return rb_io_s_popen(argc, argv, rb_cIO);
}
}
}
}
if (redirect) {
VALUE io = rb_funcall2(argv[0], to_open, argc-1, argv+1);
if (rb_block_given_p()) {
return rb_ensure(rb_yield, io, io_close, io);
}
return io;
}
return rb_io_s_open(argc, argv, rb_cFile);
}
prints arguments in pretty form.
pp returns argument(s).
# File lib/pp.rb, line 13 def pp(*objs) # :doc: objs.each {|obj| PP.pp(obj) } objs.size <= 1 ? objs.first : objs end
When RubyGems is required, #require is replaced with our own which is capable of loading gems on demand.
When you call require 'x', this is what happens:
-
If the file can be loaded from the existing Ruby loadpath, it is.
-
Otherwise, installed gems are searched for a file that matches. If it's found in gem 'y', that gem is activated (added to the loadpath).
The normal require functionality of returning false if that
file has already been loaded is preserved.
# File lib/rubygems/core_ext/kernel_require.rb, line 38 def require path RUBYGEMS_ACTIVATION_MONITOR.enter path = path.to_path if path.respond_to? :to_path spec = Gem.find_unresolved_default_spec(path) if spec Gem.remove_unresolved_default_spec(spec) gem(spec.name) end # If there are no unresolved deps, then we can use just try # normal require handle loading a gem from the rescue below. if Gem::Specification.unresolved_deps.empty? then begin RUBYGEMS_ACTIVATION_MONITOR.exit return gem_original_require(path) ensure RUBYGEMS_ACTIVATION_MONITOR.enter end end # If +path+ is for a gem that has already been loaded, don't # bother trying to find it in an unresolved gem, just go straight # to normal require. #-- # TODO request access to the C implementation of this to speed up RubyGems spec = Gem::Specification.find { |s| s.activated? and s.contains_requirable_file? path } begin RUBYGEMS_ACTIVATION_MONITOR.exit return gem_original_require(path) ensure RUBYGEMS_ACTIVATION_MONITOR.enter end if spec # Attempt to find +path+ in any unresolved gems... found_specs = Gem::Specification.find_in_unresolved path # If there are no directly unresolved gems, then try and find +path+ # in any gems that are available via the currently unresolved gems. # For example, given: # # a => b => c => d # # If a and b are currently active with c being unresolved and d.rb is # requested, then find_in_unresolved_tree will find d.rb in d because # it's a dependency of c. # if found_specs.empty? then found_specs = Gem::Specification.find_in_unresolved_tree path found_specs.each do |found_spec| found_spec.activate end # We found +path+ directly in an unresolved gem. Now we figure out, of # the possible found specs, which one we should activate. else # Check that all the found specs are just different # versions of the same gem names = found_specs.map(&:name).uniq if names.size > 1 then raise Gem::LoadError, "#{path} found in multiple gems: #{names.join ', '}" end # Ok, now find a gem that has no conflicts, starting # at the highest version. valid = found_specs.select { |s| s.conflicts.empty? }.last unless valid then le = Gem::LoadError.new "unable to find a version of '#{names.first}' to activate" le.name = names.first raise le end valid.activate end begin RUBYGEMS_ACTIVATION_MONITOR.exit return gem_original_require(path) ensure RUBYGEMS_ACTIVATION_MONITOR.enter end rescue LoadError => load_error if load_error.message.start_with?("Could not find") or (load_error.message.end_with?(path) and Gem.try_activate(path)) then begin RUBYGEMS_ACTIVATION_MONITOR.exit return gem_original_require(path) ensure RUBYGEMS_ACTIVATION_MONITOR.enter end end raise load_error ensure RUBYGEMS_ACTIVATION_MONITOR.exit end
An alias for Psych.dump_stream meant to be used with IRB.
# File ext/psych/lib/psych/y.rb, line 4 def y *objects puts Psych.dump_stream(*objects) end