system([env,] command... [,options]) â true, false or nil Instance Public methods 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 no

test(cmd, file1 [, file2] ) â obj Instance Public methods 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" | boolea

throw(tag [, obj]) Instance Public methods 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.

trace_var(symbol, cmd ) â niltrace_var(symbol) {|val| block } â nil Instance Public methods 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 {|

Signal.trap( signal, command ) â objSignal.trap( signal ) {| | block } â obj Instance Public methods Specifies the handling of signals. The first parameter is a signal name (a string such as âSIGALRM'', âSIGUSR1'', and so on) or a signal number. The characters âSIG'' 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 âIGNORE'' or âSIG_IGN'', the signal will be ignored. If the command is âDEFAUL

untrace_var(symbol [, cmd] ) â array or nil Instance Public methods 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.

warn(msg, ...) â nil Instance Public methods 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

gem(gem_name, *requirements) Instance Private methods 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 â= example.version.numberâ. 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, Kernel#require will do the right thing for you. #gem returns true if the gem was activated, otherwise fal

pp(*objs) Instance Private methods prints arguments in pretty form. pp returns argument(s).

scanf(format, &b) Instance Private methods Scans STDIN for data matching format. See IO#scanf for details. See Scanf for details on creating a format string. You will need to require 'scanf' to use #scanf.