Ruby in a Nutshell

Command-Line Options

Like most scripting language interpreters, Ruby is generally run from the command line. The interpreter can be invoked with the following options, which control the environment and behavior of the interpreter itself:

ruby [ options ] [—] [ programfile ] [ argument... ]

-a

Used with -n or -p to split each line. Split output is stored in $F.

-c

Checks syntax only, without executing program.

-C dir

Changes directory before executing (equivalent to -X).

-d

Enables debug mode (equivalent to -debug). Sets $DEBUG to true.

-e prog

Specifies prog as the program from the command line. Specify multiple -e options for multiline programs.

-F pat

Specifies pat as the default separator pattern ($;) used by split.

-h

Displays an overview of command-line options (equivalent to -help).

-i [ext]

Overwrites the file contents with program output. The original file is saved with the extension ext. If ext isn’t specified, the original file is deleted.

-I dir

Adds dir as the directory for loading libraries.

-K [kcode]

Specifies the multibyte character set code (e or E for EUC (extended Unix code); s or S for SJIS (Shift-JIS); u or U for UTF-8; and a, A, n, or N for ASCII).

-l

Enables automatic line-end processing. Chops a newline from input lines and appends a newline to output lines.

-n

Places code within an input loop (as in while gets; ... end).

-0[octal]

Sets default record separator ($/) as an octal. Defaults to \0 if octal not specified.

-p

Places code within an input loop. Writes $_ for each ...