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Ruby Programming
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Command-Line Options

-0[octal}
' The number ``0'' flag specifies the record separator character (\0, if no digit follows). -00 indicates paragraph mode: records are separated by two successive default record separator characters. -0777 reads the entire file at once (as it is an illegal character). Sets $/.

-a
' Auto split mode when used with -n or -p; equivalent to executing {$F at the top of each loop iteration.

-C directory
' Changes working directory to directory before executing.

-c
' Checks syntax only; does not execute the program.

--copyright
Prints the copyright notice and exits.

-d, --debug
' Sets $DEBUG to true. This can be used by your programs to enable additional tracing.

-e 'command'
' Executes command as one line of Ruby source. Several -e's are allowed, and the commands are treated as multiple lines in the same program. If programfile is omitted when -e is present, execution stops after the -e commands have been run.

-F pattern
' Specifies the input field separator ($;) used as the default for split() (affects -a).

-h, --help
' Displays a short help screen.

-I directories
' Specifies directories to be prepended to $LOAD_PATH ($:). Multiple -I options may be present, and multiple directories may appear following each -I. Directories are separated by a ``:'' on Unix-like systems and by a ``;'' on DOS/Windows systems.

-i [extension}
' Edits ARGV files in place. For each file named in ARGV, anything you write to standard output will be saved back as the contents of that file. A backup copy of the file will be made if extension is supplied.
% ruby -pi.bak -e "gsub(/Perl/, 'Ruby')" *.txt

-K kcode
' Specifies the code set to be used. This option is useful mainly when Ruby is used for Japanese-language processing. kcode may be one of: e, E for EUC; s, S for SJIS; u, U for UTF-8; or a, A, n, N for ASCII.

-l
' Enables automatic line-ending processing; sets $\ to the value of $/ and chops every input line automatically.

-n
' Assumes ``while gets; ...; end'' loop around your program. For example, a simple grep command might be implemented as:
% ruby -n -e "print if /wombat/"  *.txt

-p
' Places your program code within the loop ``while gets; ...; print; end.''
% ruby -p -e "$_.downcase!" *.txt
-r library
' requires the named library before executing.

-S
' Looks for the program file using RUBYPATH or PATH environment variable.

-s
' Any command line switches found after the program filename, but before any filename arguments or before a --, are removed from ARGV and set to a global variable named for the switch. In the following example, the effect of this would be to set the variable $opt to ``electric''.

% ruby -s prog -opt=electric ./mydata

-T[level}
' Sets the safe level, which among other things enables tainting checks (see page 253). Sets $SAFE.

-v, --verbose
' Enables verbose mode and print the version number. In verbose mode, compilation warnings are printed. If no program filename appears on the command line, Ruby exits.

--version
Displays the Ruby version number and exits.

-w
' Enables verbose mode. Unlike -v, reads program from standard input if no program files are present on the command line. We recommend running your Ruby programs with -w.

-X directory
' Changes working directory to directory before executing. Same as -C directory.

-x [directory}
' Strips off text before #!ruby line and changes working directory to directory if given.

-y, --yydebug
' Enables yacc debugging in the parser (waaay too much information).
Ruby Programming
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