RUBY(1)

📦 version 3.2.3, in ubuntu noble

💎 RUBY(1) — Ruby Programmer's Reference Guide 💎

okay bestie, sit DOWN, because we're about to talk about ruby and this is genuinely one of the most iconic things in the whole manual set 🫶

✨ NAME ✨

ruby — Interpreted object-oriented scripting language 💅

✨ SYNOPSIS ✨

like, here's the whole vibe in one breath:

ruby [--copyright] [--version] [-SUacdlnpswvy] [-0[octal]]
     [-C directory] [-E external[:internal]] [-F[pattern]]
     [-I directory] [-K[c]] [-T[level]] [-W[level]] [-e command]
     [-i[extension]] [-r library] [-x[directory]]
     [--{enable|disable}-FEATURE] [--dump=target] [--verbose] [--]
     [program_file] [argument ...]

no cap, that's a LOT of flags, and yes, we're getting to every single one of them. not me gatekeeping a single option. 🙈

✨ DESCRIPTION ✨

so Ruby is an interpreted scripting language made for quick and easy object-oriented programming. she's got a whole arsenal of features for processing text files and doing system management tasks — think Perl energy, but make it cute 💖. She's simple, straightforward, and extensible. periodt.

if you're looking for a language that does easy object-oriented programming, or you simply cannot with the Perl ugliness 😭, or you're lowkey obsessed with the concept of LISP but the parentheses are giving you a headache — Ruby might just be your language of choice. the vibe check passes. 🔥

✨ FEATURES ✨

okay so here's the full rundown of what Ruby's features are, and bestie, she ate:

Interpretive

Ruby is an interpreted language, so you literally don't have to recompile programs written in Ruby to execute them. write it, run it, slay. ✨

Variables have no type (dynamic typing)

Variables in Ruby can contain data of any type. no stressing about variable typing, no crying over declarations. consequently — and this is the tradeoff, bestie, listen — it has a weaker compile time check. 👀

No declaration needed

You can use variables in your Ruby programs without any declarations at all. Variable names denote their scope — global, class, instance, or local. the name tells you everything, iykyk. 🎀

Simple syntax

Ruby has a simple syntax influenced slightly from Eiffel. simple! clean! iconic! 💅

No user-level memory management

Ruby has automatic memory management. objects that are no longer referenced from anywhere get automatically collected by the garbage collector built into the interpreter. so you just... don't think about it. she handles it. 🧚

Everything is an object

Ruby is a purely object-oriented language, and has been so since its creation. even such basic data as integers are seen as objects. everything. is. an. object. main character energy from day one. 👑

Class, inheritance, and methods

Being an object-oriented language, Ruby naturally has basic features like classes, inheritance, and methods. the fundamentals, and she's got them fr fr.

Singleton methods

Ruby has the ability to define methods for certain objects. for example, you can define a press-button action for a certain widget by defining a singleton method for the button 🎀. or — if you want to get ambitious — you can make up your own prototype based object system using singleton methods. go off. 🔥

Mix-in by modules

Ruby intentionally does not have multiple inheritance, because it is a source of confusion. instead, Ruby has the ability to share implementations across the inheritance tree. this is often called a ‘Mix-in’. she said "no chaos, only sharing." 💖

Iterators

Ruby has iterators for loop abstraction. loops but cuter, basically. 🌸

Closures

In Ruby, you can objectify the procedure. ✨

Text processing and regular expressions

Ruby has a bunch of text processing features like in Perl. regex girlies, this one's for you 🫶

M17N, character set independent

Ruby supports multilingualized programming. easy to process texts written in many different natural languages and encoded in many different character encodings, without dependence on Unicode. multilingual and unbothered 💜

Bignums

with built-in bignums, you can for example calculate factorial(400). big numbers, no problem. 🔢

Reflection and domain specific languages

Class is also an instance of the Class class. definition of classes and methods is an expression just as 1+1 is. so your programs can even write and modify programs. thus you can write your application in your own programming language on top of Ruby. this is genuinely unhinged and I'm obsessed 😭🔥

Exception handling

As in Java(tm). 💀

Direct access to the OS

Ruby can use most Unix system calls, often used in system programming. she talks to the kernel directly, bestie. 🌈

Dynamic loading

On most Unix systems, you can load object files into the Ruby interpreter on-the-fly. ✨

Rich libraries

in addition to the “builtin libraries” and “standard libraries” that are bundled with Ruby, a vast amount of third-party libraries — “gems” 💎 — are available via the package management system called ‘RubyGems’, namely the gem(1) command.

visit RubyGems.org (https://rubygems.org/) to find the gems you need, and explore GitHub (https://github.com/) to see how they are being developed and used. 🎀

okay that's the whole vibe so far bestie, and we're only just getting started — more parts incoming, don't go anywhere 💖

✨ OPTIONS ✨

okay bestie, the Ruby interpreter accepts the following command-line options (switches), and they are quite similar to those of perl(1). like, same family energy, no cap. 💖

  • --copyright — Prints the copyright notice, and quits immediately without running any script. 💅
  • --version — Prints the version of the Ruby interpreter, and quits immediately without running any script. ✨
  • -0[octal] — (The digit “zero”.) Specifies the input record separator ($/) as an octal number. If no digit is given, the null character is taken as the separator. Other switches may follow the digits. -00 turns Ruby into paragraph mode. -0777 makes Ruby read whole file at once as a single string since there is no legal character with that value. 😭
  • -C directory, -X directory — Causes Ruby to switch to the directory. 🦋
  • -E external[:internal], --encoding external[:internal] — Specifies the default value(s) for external encodings and internal encoding. Values should be separated with colon (:). You can omit the one for internal encodings, then the value (Encoding.default_internal) will be nil. 💜
  • --external-encoding=encoding, --internal-encoding=encoding — Specify the default external or internal character encoding. 🌸
  • -F pattern — Specifies input field separator ($;). 🎀
  • -I directory — Used to tell Ruby where to load the library scripts. Directory path will be added to the load-path variable ($:). 📚
  • -K kcode — Specifies KANJI (Japanese) encoding. The default value for script encodings (__ENCODING__) and external encodings (Encoding.default_external) will be the specified one. kcode can be one of:
    • e — EUC-JP
    • s — Windows-31J (CP932)
    • u — UTF-8
    • n — ASCII-8BIT (BINARY)
  • -S — Makes Ruby use the PATH environment variable to search for script, unless its name begins with a slash. This is used to emulate #! on machines that don't support it, in the following manner:
#! /usr/local/bin/ruby
# This line makes the next one a comment in Ruby \
  exec /usr/local/bin/ruby -S $0 $*

On some systems $0 does not always contain the full pathname, so you need the -S switch to tell Ruby to search for the script if necessary (to handle embedded spaces and such). A better construct than $* would be ${1+"$@"}, but it does not work if the script is being interpreted by csh(1). 😤

  • -T[level=1] — Turns on taint checks at the specified level (default 1). 🫶
  • -U — Sets the default value for internal encodings (Encoding.default_internal) to UTF-8. 🌈
  • -W[level=2] — Turns on verbose mode at the specified level without printing the version message at the beginning. The level can be:
    • 0 — Verbose mode is "silence". It sets the $VERBOSE to nil.
    • 1 — Verbose mode is "medium". It sets the $VERBOSE to false.
    • 2 (default) — Verbose mode is "verbose". It sets the $VERBOSE to true. -W2 is the same as -w.
  • -a — Turns on auto-split mode when used with -n or -p. In auto-split mode, Ruby executes
$F = $_.split

at beginning of each loop. 🔥

  • -c — Causes Ruby to check the syntax of the script and exit without executing. If there are no syntax errors, Ruby will print “Syntax OK” to the standard output. ✅
  • -d, --debug — Turns on debug mode. $DEBUG will be set to true. 🐛
  • -e command — Specifies script from command-line while telling Ruby not to search the rest of the arguments for a script file name. 💬
  • -h, --help — Prints a summary of the options. 🙋
  • -i extension — Specifies in-place-edit mode. The extension, if specified, is added to old file name to make a backup copy. For example:
% echo matz > /tmp/junk
% cat /tmp/junk
matz
% ruby -p -i.bak -e '$_.upcase!' /tmp/junk
% cat /tmp/junk
MATZ
% cat /tmp/junk.bak
matz
  • -l — (The lowercase letter “ell”.) Enables automatic line-ending processing, which means to firstly set $\ to the value of $/, and secondly chops every line read using chomp!. ✂️
  • -n — Causes Ruby to assume the following loop around your script, which makes it iterate over file name arguments somewhat like sed -n or awk.
while gets
  ...
end
  • -p — Acts mostly same as -n switch, but print the value of variable $_ at the each end of the loop. For example:
% echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'
MATZ
  • -r library — Causes Ruby to load the library using require. It is useful when using -n or -p. 📦
  • -s — Enables some switch parsing for switches after script name but before any file name arguments (or before a --). Any switches found there are removed from ARGV and set the corresponding variable in the script. For example:
#! /usr/local/bin/ruby -s
# prints "true" if invoked with `-xyz' switch.
print "true\n" if $xyz
  • -v — Enables verbose mode. Ruby will print its version at the beginning and set the variable $VERBOSE to true. Some methods print extra messages if this variable is true. If this switch is given, and no other switches are present, Ruby quits after printing its version. 📣
  • -w — Enables verbose mode without printing version message at the beginning. It sets the $VERBOSE variable to true. ⚠️
  • -x[directory] — Tells Ruby that the script is embedded in a message. Leading garbage will be discarded until the first line that starts with “#!” and contains the string, “ruby”. Any meaningful switches on that line will be applied. The end of the script must be specified with either EOF, ^D (control-D), ^Z (control-Z), or the reserved word __END__. If the directory name is specified, Ruby will switch to that directory before executing script. 🧚
  • -y, --yydebug — DO NOT USE. Turns on compiler debug mode. Ruby will print a bunch of internal state messages during compilation. Only specify this switch you are going to debug the Ruby interpreter. 💀
  • --disable-FEATURE, --enable-FEATURE — Disables (or enables) the specified FEATURE.
    • --disable-gems, --enable-gems — Disables (or enables) RubyGems libraries. By default, Ruby will load the latest version of each installed gem. The Gem constant is true if RubyGems is enabled, false if otherwise. 💎
    • --disable-rubyopt, --enable-rubyopt — Ignores (or considers) the RUBYOPT environment variable. By default, Ruby considers the variable. 🌿
    • --disable-all, --enable-all — Disables (or enables) all features. 🚨
  • --dump=target — Dump some information. Prints the specified target. target can be one of:
    • version — Print version description (same as --version).
    • usage — Print a brief usage message (same as -h).
    • help — Show long help message (same as --help).
    • syntax — Check syntax (same as -c --yydebug).

Or one of the following, which are intended for debugging the interpreter:

  • yydebug — Enable compiler debug mode (same as --yydebug).
  • parsetree — Print a textual representation of the Ruby AST for the program.
  • parsetree_with_comment — Print a textual representation of the Ruby AST for the program, but with each node annoted with the associated Ruby source code.
  • insns — Print a list of disassembled bytecode instructions.
  • insns_without_opt — Print the list of disassembled bytecode instructions before various optimizations have been applied.
  • --verbose — Enables verbose mode without printing version message at the beginning. It sets the $VERBOSE variable to true. If this switch is given, and no script arguments (script file or -e options) are present, Ruby quits immediately. 👑

🌸 ENVIRONMENT 🌸

Okay bestie, listen up, because these env vars are the ones you set in your shell profile and then forget about for a year 💀

  • RUBYLIB — a colon-separated list of directories that get added to Ruby's library load path ($:). The dirs from this variable get searched before the standard load path is even looked at. like:
RUBYLIB="$HOME/lib/ruby:$HOME/lib/rubyext"
  • RUBYOPT — extra Ruby options, bestie. like:
RUBYOPT="-w -Ke"
Heads up fr fr: RUBYOPT can contain only -d, -E, -I, -K, -r, -T, -U, -v, -w, -W, --debug, --disable-FEATURE and --enable-FEATURE. That's the whole guest list, no plus-ones. 🙈
  • RUBYPATH — a colon-separated list of directories Ruby searches for Ruby programs when the -S flag is specified. This variable comes before the PATH environment variable. main character energy ✨
  • RUBYSHELL — the path to the system shell command. This one is enabled for only mswin32, mingw32, and OS/2 platforms. If it's not defined, Ruby refers to COMSPEC. very niche, very specific, we respect it 🎀
  • PATH — Ruby refers to the PATH environment variable when calling Kernel#system.

And Ruby depends on some RubyGems-related environment variables too, unless RubyGems is disabled. See the help of gem(1) like this:

% gem help

🗑️ GC ENVIRONMENT 🗑️

Not the garbage collection you're thinking of, bestie, this is the real one 💅

The Ruby garbage collector (GC) tracks objects in fixed-sized slots, but each object may have auxiliary memory allocations handled by the malloc family of C standard library calls (malloc(3), calloc(3), and realloc(3)). In this documentation, the "heap" means the Ruby object heap of fixed-sized slots, while "malloc" means auxiliary allocations — commonly called the "process heap". So there are at least two possible ways to trigger a GC:

  1. Reaching the object limit.
  2. Reaching the malloc limit.

In Ruby 2.1 the generational GC showed up (iconic), and the limits got split into young and old generations, which gives you two more ways to trigger a GC:

  1. Reaching the old object limit.
  2. Reaching the old malloc limit.

There are currently 4 possible areas where the GC may be tuned by these 11 environment variables:

  • RUBY_GC_HEAP_INIT_SLOTS — initial allocation slots. Introduced in Ruby 2.1, default: 10000.
  • RUBY_GC_HEAP_FREE_SLOTS — prepare at least this many slots after GC. Allocate this number of slots if there aren't enough slots. Introduced in Ruby 2.1, default: 4096.
  • RUBY_GC_HEAP_GROWTH_FACTOR — increase the allocation rate of heap slots by this factor. Introduced in Ruby 2.1, default: 1.8, minimum: 1.0 (no growth).
  • RUBY_GC_HEAP_GROWTH_MAX_SLOTS — allocation rate is limited to this number of slots, which prevents excessive allocation due to RUBY_GC_HEAP_GROWTH_FACTOR. Introduced in Ruby 2.1, default: 0 (no limit).
  • RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR — perform a full GC when the number of old objects is more than R * N, where R is this factor and N is the number of old objects after the last full GC. Introduced in Ruby 2.1.1, default: 2.0.
  • RUBY_GC_MALLOC_LIMIT — the initial limit of young generation allocation from the malloc-family. GC will start when this limit is reached. Default: 16MB.
  • RUBY_GC_MALLOC_LIMIT_MAX — the maximum limit of young generation allocation from malloc before GC starts. Prevents excessive malloc growth due to RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR. Introduced in Ruby 2.1, default: 32MB.
  • RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR — increases the limit of young generation malloc calls, reducing GC frequency but increasing malloc growth until RUBY_GC_MALLOC_LIMIT_MAX is reached. Introduced in Ruby 2.1, default: 1.4, minimum: 1.0 (no growth).
  • RUBY_GC_OLDMALLOC_LIMIT — the initial limit of old generation allocation from malloc; a full GC will start when this limit is reached. Introduced in Ruby 2.1, default: 16MB.
  • RUBY_GC_OLDMALLOC_LIMIT_MAX — the maximum limit of old generation allocation from malloc before a full GC starts. Prevents excessive malloc growth due to RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR. Introduced in Ruby 2.1, default: 128MB.
  • RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR — increases the limit of old generation malloc allocation, reducing full GC frequency but increasing malloc growth until RUBY_GC_OLDMALLOC_LIMIT_MAX is reached. Introduced in Ruby 2.1, default: 1.2, minimum: 1.0 (no growth).

🧵 STACK SIZE ENVIRONMENT 🧵

Okay so these ones are implementation-dependent and subject to change with different versions of Ruby — so don't @ me if they shift, bestie 🫶

The VM stack is used for pure-Ruby code and is managed by the virtual machine. The machine stack is used by the operating system, and its usage depends on C extensions as well as C compiler options.

Using lower values for these may let applications keep more Fibers or Threads running — but it increases the chance of SystemStackError exceptions and segmentation faults (SIGSEGV). 😭 So like, tread carefully, that's not a fun vibe.

These environment variables are available since Ruby 2.0.0. All values are specified in bytes.

  • RUBY_THREAD_VM_STACK_SIZE — VM stack size used at thread creation. default: 524288 (32-bit CPU) or 1048575 (64-bit)
  • RUBY_THREAD_MACHINE_STACK_SIZE — machine stack size used at thread creation. default: 524288 or 1048575
  • RUBY_FIBER_VM_STACK_SIZE — VM stack size used at fiber creation. default: 65536 or 131072
  • RUBY_FIBER_MACHINE_STACK_SIZE — machine stack size used at fiber creation. default: 262144 or 524288

👀 SEE ALSO 👀

🐛 REPORTING BUGS 🐛

  • Security vulnerabilities should be reported via an email to security@ruby-lang.org. Reported problems will be published after being fixed. 🤫
  • Other bugs and feature requests can be reported via the Ruby Issue Tracking System (https://bugs.ruby-lang.org/).
Do not report security vulnerabilities via this system, because it publishes the vulnerabilities immediately. Like. Immediately immediately. That's the whole point of the warning, bestie. 🙈

👑 AUTHORS 👑

Ruby is designed and implemented by Yukihiro Matsumoto <matz@netlab.jp>. a literal legend, we stan 💜

See ⟨https://bugs.ruby-lang.org/projects/ruby/wiki/Contributors⟩ for contributors to Ruby.

and that's a wrap on the whole page, bestie 🎀 This is from the UNIX manual, dated April 14, 2018, for RUBY(1). Go write something cute and chaotic, and remember: the GC is always watching 💅✨

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