Module: Kernel

Included in:
Object
Defined in:
object.c

Instance Method Summary collapse

Instance Method Details

#__method__Object #__callee__Object

Returns the name of the current method as a Symbol. If called outside of a method, it returns nil.


# File 'eval.c'

static VALUE
rb_f_method_name(void)
{
ID fname = rb_frame_caller(); /* need *caller* ID */

if (fname) {
return ID2SYM(fname);
}

#__method__Object #__callee__Object

Returns the name of the current method as a Symbol. If called outside of a method, it returns nil.


# File 'eval.c'

static VALUE
rb_f_method_name(void)
{
ID fname = rb_frame_caller(); /* need *caller* ID */

if (fname) {
return ID2SYM(fname);
}

#`String

Returns the standard output of running cmd in a subshell. The built-in syntax %x{...} uses this method. Sets $? to the process status.

`date`                   #=> "Wed Apr  9 08:56:30 CDT 2003\n"
`ls testdir`.split[1]    #=> "main.rb"
`echo oops && exit 99`   #=> "oops\n"
$?.exitstatus            #=> 99

Returns:


# File 'io.c'

static VALUE
rb_f_backquote(VALUE obj, VALUE str)
{
    volatile VALUE port;
    VALUE result;
    rb_io_t *fptr;

    SafeStringValue(str);
    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;
}

#abortObject #Kernel::abort([msg]) ⇒ Object #Process::abort([msg]) ⇒ Object

Terminate execution immediately, effectively by calling Kernel.exit(false). If msg is given, it is written to STDERR prior to terminating.


# File 'process.c'

VALUE
rb_f_abort(int argc, VALUE *argv)
{
rb_secure(4);
if (argc == 0) {
if (!NIL_P(GET_THREAD()->errinfo)) {
    ruby_error_print();
}

#Array(arg) ⇒ Array

Returns arg as an Array. First tries to call arg.to_ary, then arg.to_a.

Array(1..5)   #=> [1, 2, 3, 4, 5]

Returns:


# File 'object.c'

static VALUE
rb_f_array(VALUE obj, VALUE arg)
{
    return rb_Array(arg);
}

#at_exit { ... } ⇒ Proc

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

Yields:

Returns:


# File 'eval_jump.c'

static VALUE
rb_f_at_exit(void)
{
VALUE proc;

if (!rb_block_given_p()) {
rb_raise(rb_eArgError, "called without a block");
}

#autoloadnil

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")

Returns:

  • (nil)

# File 'load.c'

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");
}

#autoload?(name) ⇒ String?

Returns filename to be loaded if name is registered as autoload.

autoload(:B, "b")
autoload?(:B)            #=> "b"

Returns:


# File 'load.c'

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;
}

#bindingBinding

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"

Returns:


# File 'proc.c'

static VALUE
rb_f_binding(VALUE self)
{
    return rb_binding_new();
}

#block_given?Boolean #iterator?Boolean

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"

Overloads:

  • #block_given?Boolean

    Returns:

    • (Boolean)
  • #iterator?Boolean

    Returns:

    • (Boolean)

# File 'vm_eval.c'

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 &&
(cfp->lfp[0] & 0x02) == 0 &&
GC_GUARDED_PTR_REF(cfp->lfp[0])) {
return Qtrue;
}

#callcc {|cont| ... } ⇒ Object

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 Kernel::throw for an alternative mechanism for unwinding a call stack.

Yields:

  • (cont)

Returns:


# File 'cont.c'

static VALUE
rb_callcc(VALUE self)
{
volatile int called;
volatile VALUE val = cont_capture(&called);

if (called) {
return val;
}

#caller(start = 1) ⇒ Array?

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 result.

Returns nil if start is greater than the size of current execution stack.

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

Returns:


# File 'vm_eval.c'

static VALUE
rb_f_caller(int argc, VALUE *argv)
{
    VALUE level;
    int lev;

    rb_scan_args(argc, argv, "01", &level);

    if (NIL_P(level))
    lev = 1;
    else
    lev = NUM2INT(level);
    if (lev < 0)
    rb_raise(rb_eArgError, "negative level (%d)", lev);

    return vm_backtrace(GET_THREAD(), lev);
}

#catch([arg]) {|tag| ... } ⇒ Object

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.

Yields:

  • (tag)

Returns:


# File 'vm_eval.c'

static VALUE
rb_f_catch(int argc, VALUE *argv)
{
VALUE tag;

if (argc == 0) {
tag = rb_obj_alloc(rb_cObject);
}

#chompObject #chomp(string) ⇒ Object

Equivalent to $_ = $_.chomp(string). See String#chomp. Available only when -p/-n command line option specified.


# File 'ruby.c'

static VALUE
rb_f_chomp(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE str = rb_funcall3(uscore_get(), rb_intern("chomp"), argc, argv);
    rb_lastline_set(str);
    return str;
}

#chopString

Equivalent to ($_.dup).chop!, except nil is never returned. See String#chop!. Available only when -p/-n command line option specified.

Returns:


# File 'ruby.c'

static VALUE
rb_f_chop(void)
{
    VALUE str = rb_funcall3(uscore_get(), rb_intern("chop"), 0, 0);
    rb_lastline_set(str);
    return str;
}

#Complex(x[, y]) ⇒ Numeric

Returns x+i*y;

Returns:


# File 'complex.c'

static VALUE
nucomp_f_complex(int argc, VALUE *argv, VALUE klass)
{
    return rb_funcall2(rb_cComplex, id_convert, argc, argv);
}

#eval(string[, binding [, filename [,lineno]]]) ⇒ Object

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"

Returns:


# File 'vm_eval.c'

VALUE
rb_f_eval(int argc, VALUE *argv, VALUE self)
{
VALUE src, scope, vfile, vline;
const char *file = "(eval)";
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");
}

#exec([env,][,options]) ⇒ Object

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).

exec "echo *"       # echoes list of files in current directory
# never get here

exec "echo", "*"    # echoes an asterisk
# never get here

# File 'process.c'

VALUE
rb_f_exec(int argc, VALUE *argv)
{
struct rb_exec_arg earg;
#define CHILD_ERRMSG_BUFLEN 80
char errmsg[CHILD_ERRMSG_BUFLEN] = { '\0' }

#exit(status = true) ⇒ Object #Kernel::exit(status = true) ⇒ Object #Process::exit(status = true) ⇒ Object

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

# File 'process.c'

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) {
switch (status) {
  case Qtrue:
    istatus = EXIT_SUCCESS;
    break;
  case Qfalse:
    istatus = EXIT_FAILURE;
    break;
  default:
    istatus = NUM2INT(status);
#if EXIT_SUCCESS != 0
    if (istatus == 0)
    istatus = EXIT_SUCCESS;
#endif
    break;
}

#exit!(status = false) ⇒ Object

Exits the process immediately. No exit handlers are run. status is returned to the underlying system as the exit status.

Process.exit!(true)

# File 'process.c'

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) {
switch (status) {
  case Qtrue:
    istatus = EXIT_SUCCESS;
    break;
  case Qfalse:
    istatus = EXIT_FAILURE;
    break;
  default:
    istatus = NUM2INT(status);
    break;
}

#raiseObject #raise(string) ⇒ Object #raise(exception[, string [, array]]) ⇒ Object #failObject #fail(string) ⇒ Object #fail(exception[, string [, array]]) ⇒ Object

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

# File 'eval.c'

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;
}

#Float(arg) ⇒ Float

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

Returns:


# File 'object.c'

static VALUE
rb_f_float(VALUE obj, VALUE arg)
{
    return rb_Float(arg);
}

#fork { ... } ⇒ Fixnum? #fork { ... } ⇒ Fixnum?

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.

Overloads:


# File 'process.c'

static VALUE
rb_f_fork(VALUE obj)
{
rb_pid_t pid;

rb_secure(2);

switch (pid = rb_fork(0, 0, 0, Qnil)) {
  case 0:
rb_thread_atfork();
if (rb_block_given_p()) {
    int status;

    rb_protect(rb_yield, Qundef, &status);
    ruby_stop(status);
}

#format(format_string[, arguments...]) ⇒ String #sprintf(format_string[, arguments...]) ⇒ String

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.

Exapmles:

sprintf("%<foo>d : %<bar>f", { :foo => 1, :bar => 2 })
  #=> 1 : 2.000000
sprintf("%{foo}f", { :foo => 1 })
  # => "1f"

Overloads:

  • #format(format_string[, arguments...]) ⇒ String

    Returns:

  • #sprintf(format_string[, arguments...]) ⇒ String

    Returns:


# File 'object.c'

VALUE
rb_f_sprintf(int argc, const VALUE *argv)
{
    return rb_str_format(argc - 1, argv + 1, GETNTHARG(0));
}

#gets(sep = $/) ⇒ String? #gets(limit) ⇒ String? #gets(sep, limit) ⇒ String?

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.

Overloads:


# File 'io.c'

static VALUE
rb_f_gets(int argc, VALUE *argv, VALUE recv)
{
if (recv == argf) {
return argf_gets(argc, argv, argf);
}

#global_variablesArray

Returns an array of the names of global variables.

global_variables.grep /std/   #=> [:$stdin, :$stdout, :$stderr]

Returns:


# File 'eval.c'

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)));
}

#gsub(pattern, replacement) ⇒ String #gsub(pattern) {|...| ... } ⇒ String

Equivalent to $_.gsub..., except that $_ receives the modified result. Available only when -p/-n command line option specified.

Overloads:

  • #gsub(pattern, replacement) ⇒ String

    Returns:

  • #gsub(pattern) {|...| ... } ⇒ String

    Yields:

    • (...)

    Returns:


# File 'ruby.c'

static VALUE
rb_f_gsub(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE str = rb_funcall3(uscore_get(), rb_intern("gsub"), argc, argv);
    rb_lastline_set(str);
    return str;
}

#Integer(arg, base = 0) ⇒ Integer

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.

Integer(123.999)    #=> 123
Integer("0x1a")     #=> 26
Integer(Time.new)   #=> 1204973019
Integer("0930", 10) #=> 930
Integer("111", 2)   #=> 7

Returns:


# File 'object.c'

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);
}

#block_given?Boolean #iterator?Boolean

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"

Overloads:

  • #block_given?Boolean

    Returns:

    • (Boolean)
  • #iterator?Boolean

    Returns:

    • (Boolean)

# File 'vm_eval.c'

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 &&
(cfp->lfp[0] & 0x02) == 0 &&
GC_GUARDED_PTR_REF(cfp->lfp[0])) {
return Qtrue;
}

#lambda {|...| ... } ⇒ Proc

Equivalent to Proc.new, except the resulting Proc objects check the number of parameters passed when called.

Yields:

  • (...)

Returns:


# File 'proc.c'

static VALUE
proc_lambda(void)
{
    return rb_block_lambda();
}

#load(filename, wrap = false) ⇒ 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.

Returns:

  • (true)

# File 'load.c'

static VALUE
rb_f_load(int argc, VALUE *argv)
{
VALUE fname, wrap, path;

rb_scan_args(argc, argv, "11", &fname, &wrap);
path = rb_find_file(FilePathValue(fname));
if (!path) {
if (!rb_file_load_ok(RSTRING_PTR(fname)))
    load_failed(fname);
path = fname;
}

#local_variablesArray

Returns the names of the current local variables.

fred = 1
for i in 1..10
   # ...
end
local_variables   #=> [:fred, :i]

Returns:


# File 'vm_eval.c'

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));
}

#loop { ... } ⇒ Object #loopObject

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.

Overloads:

  • #loop { ... } ⇒ Object

    Yields:


# File 'vm_eval.c'

static VALUE
rb_f_loop(VALUE self)
{
    RETURN_ENUMERATOR(self, 0, 0);
    rb_rescue2(loop_i, (VALUE)0, 0, 0, rb_eStopIteration, (VALUE)0);
    return Qnil;        /* dummy */
}

#open(path[, mode_enc [, perm]][, opt]) ⇒ IO? #open(path[, mode_enc [, perm]][, opt]) {|io| ... } ⇒ Object

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_enc 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 "mode", "mode:ext_enc", or "mode:ext_enc:int_enc". The mode is one of the following:

r: read (default)
w: write
a: append

The mode can be followed by "b" (means binary-mode), or "+" (means both reading and writing allowed) or both. If ext_enc (external encoding) is specified, read string will be tagged by the encoding in reading, and output string will be converted to the specified encoding in writing. If ext_enc starts with 'BOM|', check whether the input has a BOM. If there is a BOM, strip it and set external encoding as what the BOM tells. If there is no BOM, use ext_enc without 'BOM|'. If two encoding names, ext_enc and int_enc (external encoding and internal encoding), are specified, the read string is converted from ext_enc to int_enc then tagged with the int_enc in read mode, and in write mode, the output string will be converted from int_enc to ext_enc before writing.

If a file is being created, its initial permissions may be set using the integer third parameter.

If a block is specified, it will be invoked with the File object as a parameter, and the file 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 "|'' is a single minus sign, Ruby forks, and this subprocess is connected to the parent. In the subprocess, the open call returns nil. If the command is not "-'', the subprocess runs the command. If a block is associated with an open("|-") call, that block will be 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.

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 I/O object:

open("|-") do |f|
  if f == nil
    puts "in Child"
  else
    puts "Got: #{f.gets}"
  end
end

produces:

Got: in Child

Overloads:

  • #open(path[, mode_enc [, perm]][, opt]) ⇒ IO?

    Returns:

    • (IO, nil)
  • #open(path[, mode_enc [, perm]][, opt]) {|io| ... } ⇒ Object

    Yields:

    • (io)

    Returns:


# File 'io.c'

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;
}

#p(obj) ⇒ Object #p(obj1, obj2, ...) ⇒ Array #pnil

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">

Overloads:

  • #p(obj) ⇒ Object

    Returns:

  • #p(obj1, obj2, ...) ⇒ Array

    Returns:

  • #pnil

    Returns:

    • (nil)

# File 'io.c'

static VALUE
rb_f_p(int argc, VALUE *argv, VALUE self)
{
int i;
VALUE ret = Qnil;

for (i=0; i<argc; i++) {
rb_p(argv[i]);
}

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

Returns:

  • (nil)

# File 'io.c'

static VALUE
rb_f_print(int argc, VALUE *argv)
{
    rb_io_print(argc, argv, rb_stdout);
    return Qnil;
}

#printf(io, string[, obj ... ]) ⇒ nil #printf(string[, obj ... ]) ⇒ nil

Equivalent to:

io.write(sprintf(string, obj, ...)

or

$stdout.write(sprintf(string, obj, ...)

Overloads:

  • #printf(io, string[, obj ... ]) ⇒ nil

    Returns:

    • (nil)
  • #printf(string[, obj ... ]) ⇒ nil

    Returns:

    • (nil)

# File 'io.c'

static VALUE
rb_f_printf(int argc, VALUE *argv)
{
VALUE out;

if (argc == 0) return Qnil;
if (TYPE(argv[0]) == T_STRING) {
out = rb_stdout;
}

#proc {|...| ... } ⇒ Proc

Equivalent to Proc.new.

Yields:

  • (...)

Returns:


# File 'proc.c'

VALUE
rb_block_proc(void)
{
    return proc_new(rb_cProc, FALSE);
}

#putc(int) ⇒ Integer

Equivalent to:

$stdout.putc(int)

Refer to the documentation for IO#putc for important information regarding multi-byte characters.

Returns:


# File 'io.c'

static VALUE
rb_f_putc(VALUE recv, VALUE ch)
{
if (recv == rb_stdout) {
return rb_io_putc(recv, ch);
}

#puts(obj, ...) ⇒ nil

Equivalent to

$stdout.puts(obj, ...)

Returns:

  • (nil)

# File 'io.c'

static VALUE
rb_f_puts(int argc, VALUE *argv, VALUE recv)
{
if (recv == rb_stdout) {
return rb_io_puts(argc, argv, recv);
}

#raiseObject #raise(string) ⇒ Object #raise(exception[, string [, array]]) ⇒ Object #failObject #fail(string) ⇒ Object #fail(exception[, string [, array]]) ⇒ Object

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

# File 'eval.c'

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;
}

#rand(max = 0) ⇒ Numeric

If max is Range, returns a pseudorandom number where range.member(number) == true.

Or else converts max to an integer using max1 = max.to_i.abs.

Then if max is nil the result is zero, returns a pseudorandom floating point number greater than or equal to 0.0 and less than 1.0.

Otherwise, returns a pseudorandom integer greater than or equal to zero and less than max1.

Kernel::srand may be used to ensure repeatable sequences of random numbers between different runs of the program. Ruby currently uses a modified Mersenne Twister with a period of 2**19937-1.

srand 1234                 #=> 0
[ rand,  rand ]            #=> [0.191519450163469, 0.49766366626136]
[ rand(10), rand(1000) ]   #=> [6, 817]
srand 1234                 #=> 1234
[ rand,  rand ]            #=> [0.191519450163469, 0.49766366626136]

Returns:


# File 'random.c'

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;
}

#Rational(x[, y]) ⇒ Numeric

Returns x/y;

Returns:


# File 'rational.c'

static VALUE
nurat_f_rational(int argc, VALUE *argv, VALUE klass)
{
    return rb_funcall2(rb_cRational, id_convert, argc, argv);
}

#readline(sep = $/) ⇒ String #readline(limit) ⇒ String #readline(sep, limit) ⇒ String

Equivalent to Kernel::gets, except readline raises EOFError at end of file.

Overloads:


# File 'io.c'

static VALUE
rb_f_readline(int argc, VALUE *argv, VALUE recv)
{
if (recv == argf) {
return argf_readline(argc, argv, argf);
}

#readlines(sep = $/) ⇒ Array #readlines(limit) ⇒ Array #readlines(sep, limit) ⇒ Array

Returns an array containing the lines returned by calling Kernel.gets(sep) until the end of file.

Overloads:


# File 'io.c'

static VALUE
rb_f_readlines(int argc, VALUE *argv, VALUE recv)
{
if (recv == argf) {
return argf_readlines(argc, argv, argf);
}

#require(name) ⇒ Boolean

Loads the given name, returning true if successful and false if the feature is already loaded.

If the filename does not resolve to an absolute path, it will be searched for in the directories listed in $LOAD_PATH ($:).

If the filename has the extension ".rb", it is loaded as a source file; if the extension is ".so", ".o", or ".dll", or the default shared library extension on the current platform, Ruby loads the shared library as a Ruby extension. Otherwise, Ruby tries adding ".rb", ".so", and so on to the name until found. If the file named cannot be found, a LoadError will be raised.

For Ruby extensions the filename given may use any shared library extension. For example, on Linux the socket extension is "socket.so" and require 'socket.dll' will load the socket extension.

The absolute path of the loaded file is added to $LOADED_FEATURES ($"). A file will not be loaded again if its path already appears in $". For example, require 'a'; require './a' will not load a.rb again.

require "my-library.rb"
require "db-driver"

Returns:

  • (Boolean)

# File 'load.c'

VALUE
rb_f_require(VALUE obj, VALUE fname)
{
    return rb_require_safe(fname, rb_safe_level());
}

#require_relative(string) ⇒ Boolean

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.

Returns:

  • (Boolean)

# File 'load.c'

VALUE
rb_f_require_relative(VALUE obj, VALUE fname)
{
VALUE base = rb_current_realfilepath();
if (NIL_P(base)) {
rb_raise(rb_eLoadError, "cannot infer basepath");
}

#select(read_array) ⇒ Object

[, error_array

[, timeout]]]) -> array  or  nil

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 IO objects that wait until ready for read

write_array

an array of IO objects that wait until ready for write

error_array

an array of IO objects 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

# File 'io.c'

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;
}

#set_trace_func(proc) ⇒ Proc #set_trace_func(nil) ⇒ nil

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, and 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), and 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

Overloads:

  • #set_trace_func(proc) ⇒ Proc

    Returns:

  • #set_trace_func(nil) ⇒ nil

    Returns:

    • (nil)

# File 'thread.c'

static VALUE
set_trace_func(VALUE obj, VALUE trace)
{
rb_remove_event_hook(call_trace_func);

if (NIL_P(trace)) {
GET_THREAD()->tracing = EVENT_RUNNING_NOTHING;
return Qnil;
}

#sleep([duration]) ⇒ Fixnum

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

Returns:


# File 'process.c'

static VALUE
rb_f_sleep(int argc, VALUE *argv)
{
time_t beg, end;

beg = time(0);
if (argc == 0) {
rb_thread_sleep_forever();
}

#spawn([env,][,options]) ⇒ Object #spawn([env,][,options]) ⇒ Object

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]
  current directory:
    :chdir => str
  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 fds (default for system and exec)
    :close_others => true  : don't inherit (default for spawn and IO.popen)

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 :chdir key in options specifies the current directory.

pid = spawn(command, :chdir=>"/var/tmp")

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 differs 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"

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.

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.


# File 'process.c'

static VALUE
rb_f_spawn(int argc, VALUE *argv)
{
rb_pid_t pid;
char errmsg[CHILD_ERRMSG_BUFLEN] = { '\0' }

#format(format_string[, arguments...]) ⇒ String #sprintf(format_string[, arguments...]) ⇒ String

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.

Exapmles:

sprintf("%<foo>d : %<bar>f", { :foo => 1, :bar => 2 })
  #=> 1 : 2.000000
sprintf("%{foo}f", { :foo => 1 })
  # => "1f"

Overloads:

  • #format(format_string[, arguments...]) ⇒ String

    Returns:

  • #sprintf(format_string[, arguments...]) ⇒ String

    Returns:


# File 'object.c'

VALUE
rb_f_sprintf(int argc, const VALUE *argv)
{
    return rb_str_format(argc - 1, argv + 1, GETNTHARG(0));
}

#srand(number = 0) ⇒ Object

Seeds the pseudorandom number generator to the value of number. If number is omitted, seeds the generator using a combination of the time, the process id, and a sequence number. (This is also the behavior if Kernel::rand is called without previously calling srand, but without the sequence.) By setting the seed to a known value, scripts can be made deterministic during testing. The previous seed value is returned. Also see Kernel::rand.


# File 'random.c'

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();
}

#String(arg) ⇒ String

Converts arg to a String by calling its to_s method.

String(self)        #=> "main"
String(self.class)  #=> "Object"
String(123456)      #=> "123456"

Returns:


# File 'object.c'

static VALUE
rb_f_string(VALUE obj, VALUE arg)
{
    return rb_String(arg);
}

#sub(pattern, replacement) ⇒ Object #sub(pattern) { ... } ⇒ Object

Equivalent to $_.sub(args), except that $_ will be updated if substitution occurs. Available only when -p/-n command line option specified.

Overloads:

  • #sub(pattern) { ... } ⇒ Object

    Yields:


# File 'ruby.c'

static VALUE
rb_f_sub(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE str = rb_funcall3(uscore_get(), rb_intern("sub"), argc, argv);
    rb_lastline_set(str);
    return str;
}

#syscall(num[, args...]) ⇒ Integer

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 syscall.h.

syscall 4, 1, "hello\n", 6   # '4' is write(2) on our box

produces:

hello

Calling syscall on a platform which does not have any way to an arbitrary system function just fails with NotImplementedError.

Note

syscall is essentially unsafe and unportable. Feel free to shoot your foot. DL (Fiddle) library is preferred for safer and a bit more portable programming.

Returns:


# File 'io.c'

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.");
}

#system([env,][,options]) ⇒ true, ...

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.

Returns:

  • (true, false, nil)

# File 'process.c'

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);

chfunc = signal(SIGCHLD, SIG_DFL);
#endif
pid = rb_spawn_internal(argc, argv, FALSE, NULL, 0);
#if defined(HAVE_FORK) || defined(HAVE_SPAWNV)
if (pid > 0) {
rb_syswait(pid);
}

#test(int_cmd, file1[, file2]) ⇒ Object

Uses the integer aCmd to perform various tests on file1 (first table below) or on file1 and file2 (second table).

File tests on a single file:

Test   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

Returns:


# File 'file.c'

static VALUE
rb_f_test(int argc, VALUE *argv)
{
int cmd;

if (argc == 0) rb_raise(rb_eArgError, "wrong number of arguments (0 for 2..3)");
cmd = NUM2CHR(argv[0]);
if (cmd == 0) goto unknown;
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]);
}

#throw(tag[, obj]) ⇒ Object

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.


# File 'vm_eval.c'

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);
    return Qnil;        /* not reached */
}

#trace_var(symbol, cmd) ⇒ nil #trace_var(symbol) {|val| ... } ⇒ nil

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'

Overloads:

  • #trace_var(symbol, cmd) ⇒ nil

    Returns:

    • (nil)
  • #trace_var(symbol) {|val| ... } ⇒ nil

    Yields:

    • (val)

    Returns:

    • (nil)

# File 'eval.c'

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();
}

#trap(signal, command) ⇒ Object #trap(signal) {|| ... } ⇒ Object

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

Overloads:


# File 'signal.c'

static VALUE
sig_trap(int argc, VALUE *argv)
{
struct trap_arg arg;

rb_secure(2);
if (argc < 1 || argc > 2) {
rb_raise(rb_eArgError, "wrong number of arguments (%d for 1..2)", argc);
}

#untrace_var(symbol[, cmd]) ⇒ Array?

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.

Returns:


# File 'eval.c'

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_to_id(var);
if (!st_lookup(rb_global_tbl, (st_data_t)id, &data)) {
	rb_name_error(id, "undefined global variable %s", rb_id2name(id));
}

#warn(msg) ⇒ nil

Display the given message (followed by a newline) on STDERR unless warnings are disabled (for example with the -W0 flag).

Returns:

  • (nil)

# File 'error.c'

static VALUE
rb_warn_m(VALUE self, VALUE mesg)
{
if (!NIL_P(ruby_verbose)) {
rb_io_write(rb_stderr, mesg);
rb_io_write(rb_stderr, rb_default_rs);
}