--- name: "ruby" section: "1" platform: "linux" package: "ruby" version: "3.4.12-1" release: "Arch Linux 2026-11-01" platforms: ["linux", "macos"] url: "https://new.carta.tech/ruby" --- # ruby(1) Interpreted object-oriented scripting language ## NAME **ruby** – Interpreted object-oriented scripting language ## SYNOPSIS **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**\[*directory*\]\] \[**--**{**enable**\|**disable**}-*FEATURE*\] \[**--dump**=*target*\] \[**--verbose**\] \[**--crash-report**=*template*\] \[**--**\] \[*program\_file*\] \[*argument* *...*\] ## DESCRIPTION Ruby is an interpreted scripting language for quick and easy object-oriented programming. It has many features to process text files and to do system management tasks (like in Perl). It is simple, straight-forward, and extensible. If you want a language for easy object-oriented programming, or you don't like the Perl ugliness, or you do like the concept of LISP, but don't like too many parentheses, Ruby might be your language of choice. ## FEATURES Ruby's features are as follows: - **Interpretive** Ruby is an interpreted language, so you don't have to recompile programs written in Ruby to execute them. - **Variables have no type (dynamic typing)** Variables in Ruby can contain data of any type. You don't have to worry about variable typing. Consequently, it has a weaker compile time check. - **No declaration needed** You can use variables in your Ruby programs without any declarations. Variable names denote their scope - global, class, instance, or local. - **Simple syntax** Ruby has a simple syntax influenced slightly from Eiffel. - **No user-level memory management** Ruby has automatic memory management. Objects no longer referenced from anywhere are automatically collected by the garbage collector built into the interpreter. - **Everything is an object** Ruby is a purely object-oriented language, and was so since its creation. Even such basic data as integers are seen as objects. - **Class, inheritance, and methods** Being an object-oriented language, Ruby naturally has basic features like classes, inheritance, and methods. - **Singleton methods** Ruby has the ability to define methods for certain objects. For example, you can define a press-button action for certain widget by defining a singleton method for the button. Or, you can make up your own prototype based object system using singleton methods, if you want to. - **Mix-in by modules** Ruby intentionally does not have the multiple inheritance as 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’. - **Iterators** Ruby has iterators for loop abstraction. - **Closures** In Ruby, you can objectify the procedure. - **Text processing and regular expressions** Ruby has a bunch of text processing features like in Perl. - **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. - **Bignums** With built-in bignums, you can for example calculate factorial(400). - **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. - **Exception handling** As in Java(tm). - **Direct access to the OS** Ruby can use most UNIX system calls, often used in system programming. - **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)](/gem/1.md) 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. ## OPTIONS The Ruby interpreter accepts the following command-line options (switches). They are quite similar to those of [perl(1)](/perl/1.md). - **--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)](/csh/1.md). - **-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.**-W** 2 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. - **--backtrace-limit**=*num* Limits the maximum length of backtraces to *num* lines (default -1, meaning no limit). - **-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** This option is not guaranteed to be compatible. 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. - **insns** Print a list of disassembled bytecode instructions. - **-optimize** Disable various optimizations to print a list disassembled bytecode instructions. - **+error-tolerant** Enable error-tolerant parsing, when yydebug or parsetree. - **+comment** Annotate a textual representation of the Ruby AST for the program with the associated Ruby source code. - **--verbose** Enables verbose mode without printing version message at the beginning. It sets the $VERBOSE variable to true. If this switch is given, and no script arguments (script file or **-e** options) are present, Ruby quits immediately. - **--crash-report**=*template* Sets the template of path name to save crash report. See RUBY\_CRASH\_REPORT environment variable for details. ## ENVIRONMENT - RUBYLIB A colon-separated list of directories that are added to Ruby's library load path ($:). Directories from this environment variable are searched before the standard load path is searched. e.g.: ``` RUBYLIB="$HOME/lib/ruby:$HOME/lib/rubyext" ``` - RUBYOPT Additional Ruby options. e.g. ``` RUBYOPT="-w -Ke" ``` Note that RUBYOPT can contain only **-d**, **-E**, **-I**, **-K**, **-r**, **-T**, **-U**, **-v**, **-w**, **-W,** **--debug**, **--disable-***FEATURE* and **--enable-***FEATURE*. - RUBYPATH A colon-separated list of directories that Ruby searches for Ruby programs when the **-S** flag is specified. This variable precedes the PATH environment variable. - RUBYSHELL The path to the system shell command. This environment variable is enabled for only mswin32, mingw32, and OS/2 platforms. If this variable is not defined, Ruby refers to COMSPEC. - RUBY\_FREE\_AT\_EXIT If set, Ruby tries to free all dynamically allocated memories. Introduced in Ruby 3.3, default: unset. - RUBY\_IO\_BUFFER\_DEFAULT\_SIZE The custom default buffer size of IO::Buffer. - RUBY\_MAX\_CPU The maximum number of native threads used by M:N Threads scheduler Introduced in Ruby 3.3, default: 8. - RUBY\_MN\_THREADS If set to 1, M:N Thread scheduler is enabled on the main Ractor. Introduced in Ruby 3.3, default: unset. - RUBY\_PAGER The pager command that will be used for - RUBY\_THREAD\_TIMESLICE Sets the default thread time slice (thread quantum) in milliseconds. Introduced in Ruby 3.4, default: 100ms. **--help** option. Introduced in Ruby 3.0, default: PAGER environment variable. - PATH Ruby refers to the PATH environment variable on calling Kernel#system. And Ruby depends on some RubyGems related environment variables unless RubyGems is disabled. See the help of [gem(1)](/gem/1.md) as below. ``` % gem help ``` ## GC ENVIRONMENT 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)](/malloc/3.md), [calloc(3)](/calloc/3.md), and [realloc(3)](/realloc/3.md)). In this documentation, the "heap" refers to the Ruby object heap of fixed-sized slots, while "malloc" refers to auxiliary allocations commonly referred to as the "process heap". Thus there are at least two possible ways to trigger GC: - **1** Reaching the object limit. - **2** Reaching the malloc limit. In Ruby 2.1, the generational GC was introduced and the limits are divided into young and old generations, providing two additional ways to trigger a GC: - **3** Reaching the old object limit. - **4** Reaching the old malloc limit. There are currently 4 possible areas where the GC may be tuned by the following environment variables: - RUBY\_GC\_HEAP\_*n*\_INIT\_SLOTS Initial allocation of slots in a specific heap. The available heaps can be found in the keys of GC.stat\_heap. *n* is a decimal number between 0 and 4. Introduced in Ruby 3.3. - RUBY\_GC\_HEAP\_FREE\_SLOTS Prepare at least this amount of slots after GC. Allocate this number slots if there are not enough slots. Introduced in Ruby 2.1, default: 4096 - RUBY\_GC\_HEAP\_GROWTH\_FACTOR Increase 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, preventing 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\_HEAP\_REMEMBERED\_WB\_UNPROTECTED\_OBJECTS\_LIMIT\_RATIO Used to calculate the remembered\_wb\_unprotected\_objects\_limit using a ratio of old\_objects. Introduced in Ruby 3.3, default: 0.1, minimum: 0.0 - 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\_HEAP\_FREE\_SLOTS\_MIN\_RATIO Allocate additional pages when the number of free slots is lower than the value (total\_slots \* (this ratio)). Introduced in Ruby 2.4, default: 0.2, minimum: 0.0, maximum: 1.0 - RUBY\_GC\_HEAP\_FREE\_SLOTS\_MAX\_RATIO Allow to free pages when the number of free slots is greater than the value (total\_slots \* (this ratio)). Introduced in Ruby 2.4, default: 0.4, minimum: RUBY\_GC\_HEAP\_FREE\_SLOTS\_MIN\_RATIO, maximum: 1.0 - RUBY\_GC\_HEAP\_FREE\_SLOTS\_GOAL\_RATIO Allocate slots to satisfy this formula: free\_slots = total\_slots \* goal\_ratio In other words, prepare (total\_slots \* goal\_ratio) free slots. if this value is 0.0, then use RUBY\_GC\_HEAP\_GROWTH\_FACTOR directly. Introduced in Ruby 2.4, default: 0.65, minimum: RUBY\_GC\_HEAP\_FREE\_SLOTS\_MIN\_RATIO, maximum: RUBY\_GC\_HEAP\_FREE\_SLOTS\_MAX\_RATIO - 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) - RUBY\_SHARED\_FIBER\_POOL\_FREE\_STACKS Frees stacks of pooled fibers, if set to 1. Do not free the stacks if set to 0. Introduced in Ruby 2.7, default: 1 (no growth) ## STACK SIZE ENVIRONMENT Stack size environment variables are implementation-dependent and subject to change with different versions of Ruby. The VM stack is used for pure-Ruby code and managed by the virtual machine. Machine stack is used by the operating system and its usage is dependent on C extensions as well as C compiler options. Using lower values for these may allow applications to keep more Fibers or Threads running; but increases the chance of SystemStackError exceptions and segmentation faults (SIGSEGV). 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 ## CRASH REPORT ENVIRONMENT - RUBY\_CRASH\_REPORT The template of path name to save crash report. default: none ### Naming crash report files The template can contain **%** specifiers which are substituted by the following values when a crash report file is created: - **%%** A single **%** character. - **%e** Basename of executable. - **%E** Pathname of executable, with slashes (**/**) replaced by exclamation marks (**!**). - **%f** Basename of the program name, $0. - **%F** Pathname of the program name, $0, with slashes (**/**) replaced by exclamation marks (**!**). - **%p** PID of dumped process. - **%t** Time of dump, expressed as seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC). - **%NNN** A character code in octal. A single **%** at the end of the template is dropped from the core filename, as is the combination of a **%** followed by any character other than those listed above. All other characters in the template become a literal part of the core filename. The template may include '/' characters, which are interpreted as delimiters for directory names. ### Piping crash reports to a program If the first character of this file is a pipe symbol (**\|**), then the remainder of the line is interpreted as the command-line for a program (or script) that is to be executed. The pipe template is split on spaces into an argument list before the template parameters are expanded. ## MISC ENVIRONMENT - RUBY\_TCP\_NO\_FAST\_FALLBACK If set to 1, disables the fast fallback feature by default in TCPSocket.new and Socket.tcp. When set to 0 or left unset, the fast fallback feature is enabled. Introduced in Ruby 3.4, default: unset. ## SEE ALSO - **https://www.ruby-lang.org/** The official web site. - **https://www.ruby-toolbox.com/** Comprehensive catalog of Ruby libraries. ## 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. ## AUTHORS Ruby is designed and implemented by Yukihiro Matsumoto ⟨matz@netlab.jp⟩. See ⟨**https://github.com/ruby/ruby/graphs/contributors**⟩ for contributors to Ruby.