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RUBY(1) Ruby Programmer's Reference Guide RUBY(1) 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 decla- rations. 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 refer- enced 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 ob- jects. 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 sin- gleton 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 of- ten 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 factor- ial(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 pro- gramming. 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 li- braries ("gems") are available via the package management sys- tem 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. OPTIONS The Ruby interpreter accepts the following command-line options (switches). They are quite similar to those of perl(1). --copyright Prints the copyright notice, and quits immediately with- out 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 separa- tor ($/) as an octal number. If no digit is given, the null character is taken as the separator. Other switches may follow the digits. -00 turns Ruby into paragraph mode. -0777 makes Ruby read whole file at once as a single string since there is no legal charac- ter with that value. -C directory -X directory Causes Ruby to switch to the directory. -E external[:internal] --encoding external[:internal] Specifies the default value(s) for external encodings and internal encoding. Values should be separated with colon (:). You can omit the one for internal encodings, then the value (Encoding.default_internal) will be nil. --external-encoding=encoding --internal-encoding=encoding Specify the default external or internal character en- coding -F pattern Specifies input field separator ($;). -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. --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. $DEBUG will be set to true. -e command Specifies script from command-line while telling Ruby not to search the rest of the arguments for a script file name. -h --help Prints a summary of the options. -i extension Specifies in-place-edit mode. The extension, if speci- fied, is added to old file name to make a backup copy. For example: % echo matz > /tmp/junk % cat /tmp/junk matz % ruby -p -i.bak -e '$_.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 exam- ple: #! /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 in- terpreter. --disable-FEATURE --enable-FEATURE Disables (or enables) the specified FEATURE. --disable-gems --enable-gems Disables (or enables) RubyGems li- braries. By default, Ruby will load the latest version of each installed gem. The Gem constant is true if RubyGems is enabled, false if other- wise. --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 debug- ging 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 instruc- tions. +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 memo- ries. 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 --help option. In- troduced in Ruby 3.0, default: PAGER environment variable. RUBY_THREAD_TIMESLICE Sets the default thread time slice (thread quantum) in mil- liseconds. Introduced in Ruby 3.4, default: 100ms. PATH Ruby refers to the PATH environment variable on calling Ker- nel#system. And Ruby depends on some RubyGems related environment variables unless RubyGems is disabled. See the help of gem(1) 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), calloc(3), and realloc(3)). In this documentation, the "heap" refers to the Ruby ob- ject heap of fixed-sized slots, while "malloc" refers to auxiliary al- locations 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 di- vided 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, de- fault: 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. Intro- duced 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 cal- culate the remembered_wb_unprotected_objects_limit us- ing 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 allo- cation 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 allo- cation from malloc before GC starts. Pre- vents excessive malloc growth due to RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR. Intro- duced in Ruby 2.1, default: 32MB. RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR Increases the limit of young genera- tion malloc calls, reducing GC frequency but increasing malloc growth until RUBY_GC_MAL- LOC_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, maxi- mum: 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 for- mula: 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 di- rectly. 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 alloca- tion 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 alloca- tion from malloc before a full GC starts. Prevents excessive malloc growth due to RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR. In- troduced in Ruby 2.1, default: 128MB RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR Increases the limit of old gener- ation malloc allocation, reducing full GC frequency but increasing malloc growth until RUBY_GC_OLDMALLOC_LIMIT_MAX is reached. In- troduced 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 sub- ject 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 exten- sions as well as C compiler options. Using lower values for these may allow applications to keep more Fibers or Threads running; but in- creases 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 1048576 (64-bit) RUBY_THREAD_MACHINE_STACK_SIZE Machine stack size used at thread cre- ation. default: 524288 or 1048576 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 cre- ation. default: 262144 or 524288 CRASH REPORT ENVIRONMENT RUBY_CRASH_REPORT The template of path name to save crash report. de- fault: none Naming crash report files The template can contain % specifiers which are substituted by the fol- lowing 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 file- name, as is the combination of a % followed by any character other than those listed above. All other characters in the template become a lit- eral part of the core filename. The template may include '/' charac- ters, 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 re- mainder 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 fea- ture by default in TCPSocket.new and Socket.tcp. When set to 0 or left unset, the fast fallback feature is enabled. In- troduced 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 secu- rity vulnerabilities via this system because it publishes the vul- nerabilities 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. UNIX April 14, 2018 RUBY(1)
NAME | SYNOPSIS | DESCRIPTION | FEATURES | OPTIONS | ENVIRONMENT | GC ENVIRONMENT | STACK SIZE ENVIRONMENT | CRASH REPORT ENVIRONMENT | MISC ENVIRONMENT | SEE ALSO | REPORTING BUGS | AUTHORS
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