[DOC] Remove an obsolete file

It has been merged into `doc/ruby/options.md` with
`field_processing.md` at ruby/ruby#10138.

1 files changed, 0 insertions, 174 deletions

diff --git a/doc/command_line/environment.md b/doc/command_line/environment.md
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-## Environment
-
-Certain command-line options affect the execution environment
-of the invoked Ruby program.
-
-### About the Examples
-
-The examples here use command-line option `-e`,
-which passes the Ruby code to be executed on the command line itself:
-
-```console
-$ ruby -e 'puts "Hello, World."'
-```
-
-### Option `-C`
-
-The argument to option `-C` specifies a working directory
-for the invoked Ruby program;
-does not change the working directory for the current process:
-
-```console
-$ basename `pwd`
-ruby
-$ ruby -C lib -e 'puts File.basename(Dir.pwd)'
-lib
-$ basename `pwd`
-ruby
-```
-
-Whitespace between the option and its argument may be omitted.
-
-### Option `-I`
-
-The argument to option `-I` specifies a directory
-to be added to the array in global variable `$LOAD_PATH`;
-the option may be given more than once:
-
-```console
-$ pushd /tmp
-$ ruby -e 'p $LOAD_PATH.size'
-8
-$ ruby -I my_lib -I some_lib -e 'p $LOAD_PATH.size'
-10
-$ ruby -I my_lib -I some_lib -e 'p $LOAD_PATH.take(2)'
-["/tmp/my_lib", "/tmp/some_lib"]
-$ popd
-```
-
-Whitespace between the option and its argument may be omitted.
-
-### Option `-r`
-
-The argument to option `-r` specifies a library to be required
-before executing the Ruby program;
-the option may be given more than once:
-
-```console
-$ ruby -e 'p defined?(JSON); p defined?(CSV)'
-nil
-nil
-$ ruby -r CSV -r JSON -e 'p defined?(JSON); p defined?(CSV)'
-"constant"
-"constant"
-```
-
-Whitespace between the option and its argument may be omitted.
-
-### Option `-0`
-
-Option `-0` defines the input record separator `$/`
-for the invoked Ruby program.
-
-The optional argument to the option must be octal digits,
-each in the range `0..7`;
-these digits are prefixed with digit `0` to form an octal value:
-
-- If no argument is given, the input record separator is `0x00`.
-- If the argument is `0`, the input record separator is `''`;
-  see {Special Line Separator Values}[rdoc-ref:IO@Special+Line+Separator+Values].
-- If the argument is in range `(1..0377)`,
-  it becomes the character value of the input record separator `$/`.
-- Otherwise, the input record separator is `nil`.
-
-Examples:
-
-```console
-$ ruby -0 -e 'p $/'
-"\x00"
-$ ruby -00 -e 'p $/'
-""
-$ ruby -012 -e 'p $/'
-"\n"
-$ ruby -015 -e 'p $/'
-"\r"
-$ ruby -0377 -e 'p $/'
-"\xFF"
-$ ruby -0400 -e 'p $/'
-nil
-```
-
-The option may not be separated from its argument by whitespace.
-
-### Option `-d`
-
-Some code in (or called by) the Ruby program may include statements or blocks
-conditioned by the global variable `$DEBUG` (e.g., `if $DEBUG`);
-these commonly write to `$stdout` or `$stderr`.
-
-The default value for `$DEBUG` is `false`;
-option `-d` (or `--debug`) sets it to `true`:
-
-```console
-$ ruby -e 'p $DEBUG'
-false
-$ ruby -d -e 'p $DEBUG'
-true
-```
-
-### Option '-w'
-
-Option `-w` (lowercase letter) is equivalent to option `-W1` (uppercase letter).
-
-### Option `-W`
-
-Any Ruby code can create a <i>warning message</i> by calling method Kernel#warn;
-methods in the Ruby core and standard libraries can also create warning messages.
-Such a message may be printed on `$stderr`
-(or not, depending on certain settings).
-
-Option `-W` helps determine whether a particular warning message
-will be written,
-by setting the initial value of global variable `$-W`:
-
-- `-W0`: Sets `$-W` to `0` (silent; no warnings).
-- `-W1`: Sets `$-W` to `1` (moderate verbosity).
-- `-W2`: Sets `$-W` to `2` (high verbosity).
-- `-W`: Same as `-W2` (high verbosity).
-- Option not given: Same as `-W1` (moderate verbosity).
-
-The value of `$-W`, in turn, determines which warning messages (if any)
-are to be printed to `$stdout` (see Kernel#warn):
-
-```console
-$ ruby -W1 -e 'p $foo'
-nil
-$ ruby -W2 -e 'p $foo'
--e:1: warning: global variable '$foo' not initialized
-nil
-```
-
-Ruby code may also define warnings for certain categories;
-these are the default settings for the defined categories:
-
-```ruby
-Warning[:experimental] # => true
-Warning[:deprecated]   # => false
-Warning[:performance]  # => false
-```
-
-They may also be set:
-
-```ruby
-Warning[:experimental] = false
-Warning[:deprecated]   = true
-Warning[:performance]  = true
-```
-
-You can suppress a category by prefixing `no-` to the category name:
-
-```console
-$ ruby -W:no-experimental -e 'p IO::Buffer.new'
-#<IO::Buffer>
-```
-