[DOC] RDoc for Open3

lib/open3.rb

@@ -482,44 +482,95 @@ class << self
     private :popen_run
   end
 
-  # Open3.capture3 captures the standard output and the standard error of a command.
+  # :call-seq:
+  #   Open3.capture3([env, ] command_line, options = {}) -> [stdout_s, stderr_s, status]
+  #   Open3.capture3([env, ] exe_path, *args, options = {}) -> [stdout_s, stderr_s, status]
   #
-  #   stdout_str, stderr_str, status = Open3.capture3([env,] cmd... [, opts])
+  # Basically a wrapper for Open3.popen3 that:
   #
-  # The arguments env, cmd and opts are passed to Open3.popen3 except
-  # <code>opts[:stdin_data]</code> and <code>opts[:binmode]</code>.  See Process.spawn.
+  # - Creates a child process, by calling Open3.popen3 with the given arguments
+  #   (except for certain entries in hash +options+; see below).
+  # - Returns as strings +stdout+ and +stderr+ the standard output
+  #   and standard error of the child process.
+  # - Returns as +status+ a <tt>Process::Status</tt> object
+  #   that represents the exit status of the child process.
   #
-  # If <code>opts[:stdin_data]</code> is specified, it is sent to the command's standard input.
+  # Returns the array <tt>[stdin_s, stdout_s, status]</tt>:
   #
-  # If <code>opts[:binmode]</code> is true, internal pipes are set to binary mode.
+  #   stdout_s, stderr_s, status = Open3.capture3('echo "Foo"')
+  #   # => ["Foo\n", "", #<Process::Status: pid 2281954 exit 0>]
+  #
+  # Like Process.spawn, this method has potential security vulnerabilities
+  # if called with untrusted input;
+  # see {Command Injection}[rdoc-ref:command_injection.rdoc].
   #
-  # Examples:
+  # Unlike Process.spawn, this method waits for the child process to exit
+  # before returning, so the caller need not do so.
   #
-  #   # dot is a command of graphviz.
-  #   graph = <<'End'
-  #     digraph g {
-  #       a -> b
-  #     }
-  #   End
-  #   drawn_graph, dot_log = Open3.capture3("dot -v", :stdin_data=>graph)
-  #
-  #   o, e, s = Open3.capture3("echo abc; sort >&2", :stdin_data=>"foo\nbar\nbaz\n")
-  #   p o #=> "abc\n"
-  #   p e #=> "bar\nbaz\nfoo\n"
-  #   p s #=> #<Process::Status: pid 32682 exit 0>
-  #
-  #   # generate a thumbnail image using the convert command of ImageMagick.
-  #   # However, if the image is really stored in a file,
-  #   # system("convert", "-thumbnail", "80", "png:#{filename}", "png:-") is better
-  #   # because of reduced memory consumption.
-  #   # But if the image is stored in a DB or generated by the gnuplot Open3.capture2 example,
-  #   # Open3.capture3 should be considered.
-  #   #
-  #   image = File.read("/usr/share/openclipart/png/animals/mammals/sheep-md-v0.1.png", :binmode=>true)
-  #   thumbnail, err, s = Open3.capture3("convert -thumbnail 80 png:- png:-", :stdin_data=>image, :binmode=>true)
-  #   if s.success?
-  #     STDOUT.binmode; print thumbnail
-  #   end
+  # Argument +options+ is a hash of options for the new process;
+  # see {Execution Options}[rdoc-ref:Process@Execution+Options].
+  #
+  # The hash +options+ is passed to method Open3.popen3;
+  # two options have local effect in method Open3.capture3:
+  #
+  # - If entry <tt>options[:stdin_data]</tt> exists, the entry is removed
+  #   and its string value is sent to the command's standard input:
+  #
+  #     Open3.capture3('tee', stdin_data: 'Foo')
+  #     # => ["Foo", "", #<Process::Status: pid 2319575 exit 0>]
+  #
+  # - If entry <tt>options[:binmode]</tt> exists, the entry us removed
+  #   the internal streams are set to binary mode.
+  #
+  # The single required argument is one of the following:
+  #
+  # - +command_line+ if it is a string,
+  #   and if it begins with a shell reserved word or special built-in,
+  #   or if it contains one or more metacharacters.
+  # - +exe_path+ otherwise.
+  #
+  # <b>Argument +command_line+</b>
+  #
+  # \String argument +command_line+ is a command line to be passed to a shell;
+  # it must begin with a shell reserved word, begin with a special built-in,
+  # or contain meta characters:
+  #
+  #   Open3.capture3('if true; then echo "Foo"; fi') # Shell reserved word.
+  #   # => ["Foo\n", "", #<Process::Status: pid 2282025 exit 0>]
+  #   Open3.capture3('echo')                         # Built-in.
+  #   # => ["\n", "", #<Process::Status: pid 2282092 exit 0>]
+  #   Open3.capture3('date > date.tmp')              # Contains meta character.
+  #   # => ["", "", #<Process::Status: pid 2282110 exit 0>]
+  #
+  # The command line may also contain arguments and options for the command:
+  #
+  #   Open3.capture3('echo "Foo"')
+  #   # => ["Foo\n", "", #<Process::Status: pid 2282092 exit 0>]
+  #
+  # <b>Argument +exe_path+</b>
+  #
+  # Argument +exe_path+ is one of the following:
+  #
+  # - The string path to an executable to be called.
+  # - A 2-element array containing the path to an executable
+  #   and the string to be used as the name of the executing process.
+  #
+  # Example:
+  #
+  #   Open3.capture3('/usr/bin/date')
+  #   # => ["Thu Sep 28 05:03:51 PM CDT 2023\n", "", #<Process::Status: pid 2282300 exit 0>]
+  #
+  # Ruby invokes the executable directly, with no shell and no shell expansion:
+  #
+  #   Open3.capture3('doesnt_exist') # Raises Errno::ENOENT
+  #
+  # If one or more +args+ is given, each is an argument or option
+  # to be passed to the executable:
+  #
+  #   Open3.capture3('echo', 'C #')
+  #   # => ["C #\n", "", #<Process::Status: pid 2282368 exit 0>]
+  #   Open3.capture3('echo', 'hello', 'world')
+  #   # => ["hello world\n", "", #<Process::Status: pid 2282372 exit 0>]
   #
   def capture3(*cmd)
     if Hash === cmd.last