青木です。

ruby の man ページに環境変数が載っていなかったので、
見よう見まねで追加しました。英語添削を希望しておきます。
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青木峰郎


Index: ruby.1
===================================================================
RCS file: /src/ruby/ruby.1,v
retrieving revision 1.12
diff -u -p -r1.12 ruby.1
--- ruby.1	20 Jan 2003 08:32:15 -0000	1.12
+++ ruby.1	21 Nov 2003 05:03:30 -0000
@@ -302,6 +302,35 @@ state messages during compiling scripts.
 this switch, unless you are going to debug the Ruby interpreter.
 .El
 .Pp
+.Sh ENVIRONMENT
+.Bl -tag -width "12"
+.Pp
+.It Sy "RUBYLIB"
+A colon-separated list of directories
+that are appended to ruby's library load path ($:).
+e.g. RUBYLIB="$HOME/lib/ruby:$HOME/lib/rubyext"
+.Pp
+.It Sy "RUBYOPT"
+Additional ruby options.
+e.g. RUBYOPT="-w -Ke"
+.Pp
+.It Sy "RUBYPATH"
+A colon-separated list of directories
+that are used when ruby searches ruby programs for "ruby -S".
+This variable precedes PATH environment variable.
+.Pp
+.It Sy "RUBYSHELL"
+The path to the system shell command.
+This environment variable is enabled for only mswin32, mingw32, and OS/2 platform.
+When this variable is not defined, ruby refers to COMSPEC.
+.Pp
+.It Sy "PATH"
+Ruby refers to PATH environment variable on calling Kernel#system.
+.Pp
+.It Sy "RUBYLIB_PREFIX"
+This variable is obsolete.
+.El
+.Pp
 .Sh AUTHORS
 Ruby is designed and implemented by
 .An Yukihiro Matsumoto Aq matz / netlab.jp .