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Ruby Programming
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class String
Parent: Object
Version: 1.6

Index:

new % * + << <=> == === =~ [ ] [ ]= ~ capitalize capitalize! center chomp chomp! chop chop! concat count crypt delete delete! downcase downcase! dump each each_byte each_line empty? gsub gsub! hash hex include? index intern length ljust next next! oct replace reverse reverse! rindex rjust scan size slice slice! split squeeze squeeze! strip strip! sub sub! succ succ! sum swapcase swapcase! to_f to_i to_s to_str tr tr! tr_s tr_s! unpack upcase upcase! upto


A String object holds and manipulates an arbitrary sequence of bytes, typically representing characters. String objects may be created using String.new or as literals (see page 202).

Because of aliasing issues, users of strings should be aware of the methods that modify the contents of a String object. Typically, methods with names ending in ``!'' modify their receiver, while those without a ``!'' return a new String. However, there are exceptions, such as String#[]= .
mixins
Comparable: <, <=, ==, >=, >, between?
Enumerable: collect, detect, each_with_index, entries, find, find_all, grep, include?, map, max, member?, min, reject, select, sort, to_a

class methods
new String.new( aString ) -> aNewString

Returns a new string object containing a copy of aString.

instance methods
% str % arg -> aString

Format---Uses str as a format specification, and returns the result of applying it to arg. If the format specification contains more than one substitution, then arg must be an Array containing the values to be substituted. See Kernel::sprintf on page 423 for details of the format string.

"%05d" % 123 "00123"
"%-5s: %08x" % [ "ID", self.id ] "ID[visible space][visible space][visible space]:[visible space]200e1670"

* str * anInteger -> aString

Copy---Returns a new String containing anInteger copies of the receiver.

"Ho! " * 3 "Ho! Ho! Ho! "

+ str + aString -> aNewString

Concatenation---Returns a new String containing aString concatenated to str.

"Hello from " + self.to_s "Hello from main"

<< str << aFixnum -> str
str << anObject -> str
Append---Concatenates the given object to str. If the object is a Fixnum between 0 and 255, it is converted to a character before concatenation.

a = "hello "
a << "world" "hello world"
a << 33 "hello world!"
a "hello world!"

<=> str <=> aString -> -1, 0, +1

Comparison---Returns -1 if str is less than, 0 if str is equal to, and +1 if str is greater than aString. If the strings are of different lengths, and the strings are equal when compared up to the shortest length, then the longer string is considered greater than the shorter one. If the variable $= is false, the comparison is based on comparing the binary values of each character in the string. If $= is not false, then the comparison is case insensitive.[The locale is ignored when case-insensitive comparisons are performed, so ``\"o'' will not match ``\"O''.]

<=> is the basis for the methods <, <=, >, >=, and between?, included from module Comparable. The method String#== does not use Comparable#== .

"abcdef" <=> "abcde" 1
"abcdef" <=> "abcdef" 0
"abcdef" <=> "abcdefg" -1
"abcdef" <=> "ABCDEF" 1
$= = true
"abcdef" <=> "ABCDEF" 0

== str == anObject -> true or false

Equality---If anObject is not a String, returns false. Otherwise, returns true if str <=> anObject returns zero.

=== str === anObject -> true or false

Case Equality---Synonym for String#== .

=~ str =~ anObject -> aFixnum or nil

Match---If anObject is a Regexp or a String, uses it as a pattern to match against str. Returns the position the match starts, or nil if there is no match. Otherwise, invokes anObject.=~, passing str as an argument. The default =~ in Object returns false.

"cat o' 9 tails" =~ "\\d" 7
"cat o' 9 tails" =~ /\d/ 7
"cat o' 9 tails" =~ 9 false

[ ] str[ aFixnum ] -> aFixnum or nil
str[ aFixnum, aFixnum ] -> aString or nil
str[ aRange ] -> aString or nil
str[ aRegexp ] -> aString or nil
str[ aString ] -> aString or nil

Element Reference---If passed a single Fixnum, returns the code of the character at that position. If passed two Fixnum objects, returns a substring starting at the offset given by the first, and a length given by the second. If given a range, a substring containing characters at offsets given by the range is returned. In all three cases, if an offset is negative, it is counted from the end of str. Returns nil if the initial offset falls outside the string, the length is negative, or the beginning of the range is greater than the end.

If a Regexp is supplied, the matching portion of str is returned. If a String is given, that string is returned if it occurs in str. In both cases, nil is returned if there is no match.

a = "hello there"
a[1] 101
a[1,3] "ell"
a[1..3] "ell"
a[-3,2] "er"
a[-4..-2] "her"
a[-2..-4] nil
a[/th[aeiou]/] "the"
a["lo"] "lo"
a["bye"] nil

[ ]= str[ aFixnum ] = aFixnum
str[ aFixnum ] = aString
str[ aFixnum, aFixnum ] = aString
str[ aRange ] = aString
str[ aRegexp ] = aString
str[ aString ] = aString

Element Assignment---Replaces some or all of the content of str. The portion of the string affected is determined using the same criteria as String#[] . If the replacement string is not the same length as the text it is replacing, the string will be adjusted accordingly. The forms that take a Fixnum will raise an IndexError if the value is out of range; the Range form will raise a RangeError, and the Regexp and String forms will silently ignore the assignment.
a = "hello"; a[2]       = 96;    a "he`lo"
a = "hello"; a[2, 4]    = "xyz"; a "hexyz"
a = "hello"; a[-4, 2]   = "xyz"; a "hxyzlo"
a = "hello"; a[2..4]    = "xyz"; a "hexyz"
a = "hello"; a[-4..-2]  = "xyz"; a "hxyzo"
a = "hello"; a[/[el]+/] = "xyz"; a "hxyzo"
a = "hello"; a["l"]     = "xyz"; a "hexyzlo"
a = "hello"; a["ll"]    = "xyz"; a "hexyzo"
a = "hello"; a["bad"]   = "xyz"; a "hello"
a = "hello"; a[2, 0]    = "xyz"; a "hexyzllo"

~ ~str -> aFixnum or nil

Equivalent to $_  =~ str .

capitalize str.capitalize -> aString

Returns a copy of str with the first character converted to uppercase and the remainder to lowercase.

"hello".capitalize "Hello"
"HELLO".capitalize "Hello"
"123ABC".capitalize "123abc"

capitalize! str.capitalize! -> str or nil

Modifies str by converting the first character to uppercase and the remainder to lowercase. Returns nil if no changes are made.
a = "hello"
a.capitalize! "Hello"
a "Hello"
a.capitalize! nil

center str.center( anInteger ) -> aString

If anInteger is greater than the length of str, returns a new String of length anInteger with str centered between spaces; otherwise, returns str.

"hello".center(4) "hello"
"hello".center(20) "[visible space][visible space][visible space][visible space][visible space][visible space][visible space]hello[visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space]"

chomp str.chomp( aString=$/ ) -> aString
Returns a new String with the given record separator removed from the end of str (if present).

"hello".chomp "hello"
"hello\n".chomp "hello"
"hello \n there".chomp "hello \n there"
"hello".chomp("llo") "he"

chomp! str.chomp!( aString=$/ ) -> str or nil

Modifies str in place as described for String#chomp , returning str, or nil if no modifications were made.
chop str.chop -> aString

Returns a new String with the last character removed. If the string ends with \r\n, both characters are removed. Applying chop to an empty string returns an empty string. String#chomp is often a safer alternative, as it leaves the string unchanged if it doesn't end in a record separator.

"string\r\n".chop "string"
"string\n\r".chop "string\n"
"string\n".chop "string"
"string".chop "strin"
"x".chop.chop ""

chop! str.chop! -> str or nil

Processes str as for String#chop , returning str, or nil if str is the empty string. See also String#chomp! .

concat str.concat( aFixnum ) -> str
str.concat( anObject ) -> str

Synonym for String#<< .

count str.count( [ aString ]+ ) -> aFixnum

Each aString parameter defines a set of characters to count. The intersection of these sets defines the characters to count in str. Any aString that starts with a caret (^) is negated. The sequence c1--c2 means all characters between c1 and c2.

a = "hello world"
a.count "lo" 5
a.count "lo", "o" 2
a.count "hello", "^l" 4
a.count "ej-m" 4

crypt str.crypt( aString ) -> aString

Applies a one-way cryptographic hash to str by invoking the standard library function crypt. The argument is the salt string, which should be two characters long, each character drawn from [a-zA-Z0-9./].

delete str.delete( [ aString ]+ ) -> aString

Returns a copy of str with all characters in the intersection of its arguments deleted. Uses the same rules for building the set of characters as String#count .

"hello".delete "l","lo" "heo"
"hello".delete "lo" "he"
"hello".delete "aeiou", "^e" "hell"
"hello".delete "ej-m" "ho"

delete! str.delete!( [ aString ]+ ) -> str or nil

Performs a delete operation in place, returning str, or nil if str was not modified.
downcase str.downcase -> aString

Returns a copy of str with all uppercase letters replaced with their lowercase counterparts. The operation is locale insensitive---only characters ``A'' to ``Z'' are affected.

"hEllO".downcase "hello"

downcase! str.downcase! -> str or nil

Downcases the contents of str, returning nil if no changes were made.
dump str.dump -> aString

Produces a version of str with all nonprinting characters replaced by \nnn notation and all special characters escaped.

each str.each( aString=$/ ) {| substr | block } -> str

Splits str using the supplied parameter as the record separator ($/ by default), passing each substring in turn to the supplied block. If a zero-length record separator is supplied, the string is split on \n characters, except that multiple successive newlines are appended together.

print "Example one\n"
"hello\nworld".each {|s| p s}
print "Example two\n"
"hello\nworld".each('l') {|s| p s}
print "Example three\n"
"hello\n\n\nworld".each('') {|s| p s}
produces:
Example one
"hello\n"
"world"
Example two
"hel"
"l"
"o\nworl"
"d"
Example three
"hello\n\n\n"
"world"

each_byte str.each_byte {| aFixnum | block }

-> str

Passes each byte in str to the given block.

"hello".each_byte {|c| print c, ' ' }
produces:
104 101 108 108 111

each_line str.each_line( aString=$/ ) {| substr | block } -> str

Synonym for String#each .

empty? str.empty? -> true or false

Returns true if str has a length of zero.

"hello".empty? false
"".empty? true

gsub str.gsub( pattern, replacement ) -> aString
str.gsub( pattern ) {| match | block }

-> aString

Returns a copy of str with all occurrences of pattern replaced with either replacement or the value of the block. If a string is used as the replacement, special variables from the match (such as $& and $1) cannot be substituted into it, as substitution into the string occurs before the pattern match starts. However, the sequences \1, \2, and so on may be used to interpolate successive groups in the match. These sequences are shown in Table 22.7 on page 371.

Backslash sequences in substitution strings
Sequence Text That Is Substituted
\1, \2, ... \9 The value matched by the nth grouped subexpression
\& The last match
\` The part of the string before the match
\' The part of the string after the match
\+ The highest-numbered group matched

In the block form, the current match is passed in as a parameter, and variables such as $1, $2, $`, $&, and $' will be set appropriately. The value returned by the block will be substituted for the match on each call.

The result inherits any tainting in the original string or any supplied replacement string.

"hello".gsub(/[aeiou]/, '*') "h*ll*"
"hello".gsub(/([aeiou])/, '<\1>') "h<e>ll<o>"
"hello".gsub('.') {|s| s[0].to_s + ' '} "104 101 108 108 111 "

gsub! str.gsub!( pattern, replacement ) -> str or nil
str.gsub!( pattern ) {| match | block }

-> str or nil

Performs the substitutions of String#gsub in place, returning str, or nil if no substitutions were performed.
hash str.hash -> aFixnum

Generates a Fixnum hash value for str. If $= is true, the hash will be case insensitive.

$= = true
hash = { 'cat' => 'Feline', 'dog' => 'canine' }
hash['cat'] "Feline"
hash['cAt'] "Feline"
$= = false
hash.rehash     # re-calculate hash values {"cat"=>"Feline", "dog"=>"canine"}
hash['cat'] "Feline"
hash['cAt'] nil

hex str.hex -> anInteger

Treats leading characters from str as a string of hexadecimal digits (with an optional sign and an optional 0x) and returns the corresponding number. Zero is returned on error.

"0x0a".hex 10
"-1234".hex -4660
"0".hex 0
"wombat".hex 0

include? str.include? aString -> true or false
str.include? aFixnum -> true or false

Returns true if str contains the given string or character.

"hello".include? "lo" true
"hello".include? "ol" false
"hello".include? ?h true

index str.index( aString [, anOffset ] ) -> aFixnum or nil
str.index( aFixnum [, anOffset ] ) -> aFixnum or nil
str.index( aRegexp [, anOffset ] ) -> aFixnum or nil

Returns the index of the first occurrence of the given substring, character, or pattern in str. Returns nil if not found. If the second parameter is present, it specifies the position in the string to begin the search.

"hello".index('e') 1
"hello".index('lo') 3
"hello".index('a') nil
"hello".index(101) 1
"hello".index(/[aeiou]/, -3) 4

intern str.intern -> aSymbol

Returns the Symbol corresponding to str, creating the symbol if it did not previously exist. See Symbol#id2name on page 384.

"Koala".intern :Koala

length str.length -> anInteger

Returns the length of str.

ljust str.ljust( anInteger ) -> aString

If anInteger is greater than the length of str, returns a new String of length anInteger with str left justified and space padded; otherwise, returns str.

"hello".ljust(4) "hello"
"hello".ljust(20) "hello[visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space]"

next str.next -> aString

Synonym for String#succ .

next! str.next! -> str

Synonym for String#succ! .

oct str.oct -> anInteger

Treats leading characters of str as a string of octal digits (with an optional sign) and returns the corresponding number. Returns 0 if the conversion fails.

"123".oct 83
"-377".oct -255
"bad".oct 0
"0377bad".oct 255

replace str.replace( aString ) -> str

Replaces the contents and taintedness of str with the corresponding values in aString.

s = "hello" "hello"
s.replace "world" "world"

reverse str.reverse -> aString

Returns a new string with the characters from str in reverse order.

"stressed".reverse "desserts"

reverse! str.reverse! -> str

Reverses str in place.
rindex str.rindex( aString [, aFixnum ] ) -> aFixnum or nil
str.rindex( aFixnum [, aFixnum ] ) -> aFixnum or nil
str.rindex( aRegexp [, aFixnum ] ) -> aFixnum or nil

Returns the index of the last occurrence of the given substring, character, or pattern in str. Returns nil if not found. If the second parameter is present, it specifies the position in the string to end the search---characters beyond this point will not be considered.

"hello".rindex('e') 1
"hello".rindex('l') 3
"hello".rindex('a') nil
"hello".rindex(101) 1
"hello".rindex(/[aeiou]/, -2) 1

rjust str.rjust( anInteger ) -> aString

If anInteger is greater than the length of str, returns a new String of length anInteger with str right justified and space padded; otherwise, returns str.

"hello".rjust(4) "hello"
"hello".rjust(20) "[visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space][visible space]hello"

scan str.scan( pattern ) -> anArray
str.scan( pattern ) {| match, ...| block } -> str

Both forms iterate through str, matching the pattern (which may be a Regexp or a String). For each match, a result is generated and either added to the result array or passed to the block. If the pattern contains no groups, each individual result consists of the matched string, $&. If the pattern contains groups, each individual result is itself an array containing one entry per group.

a = "cruel world"
a.scan(/\w+/) ["cruel", "world"]
a.scan(/.../) ["cru", "el ", "wor"]
a.scan(/(...)/) [["cru"], ["el "], ["wor"]]
a.scan(/(..)(..)/) [["cr", "ue"], ["l ", "wo"]]

And the block form:

a.scan(/\w+/) {|w| print "<<#{w}>> " }
print "\n"
a.scan(/(.)(.)/) {|a,b| print b, a }
print "\n"
produces:
<<cruel>> <<world>>
rceu lowlr

size str.size -> anInteger

Synonym for String#length .

slice str.slice( aFixnum ) -> aFixnum or nil
str.slice( aFixnum, aFixnum ) -> aString or nil
str.slice( aRange ) -> aString or nil
str.slice( aRegexp ) -> aString or nil
str.slice( aString ) -> aString or nil

Synonym for String#[ ] .

a = "hello there"
a.slice(1) 101
a.slice(1,3) "ell"
a.slice(1..3) "ell"
a.slice(-3,2) "er"
a.slice(-4..-2) "her"

a.slice(-2..-4) nil
a.slice(/th[aeiou]/) "the"
a.slice("lo") "lo"
a.slice("bye") nil

slice! str.slice!( aFixnum ) -> aFixnum or nil
str.slice!( aFixnum, aFixnum ) -> aString or nil
str.slice!( aRange ) -> aString or nil
str.slice!( aRegexp ) -> aString or nil
str.slice!( aString ) -> aString or nil

Deletes the specified portion from str, and returns the portion deleted. The forms that take a Fixnum will raise an IndexError if the value is out of range; the Range form will raise a RangeError, and the Regexp and String forms will silently ignore the assignment.
string = "this is a string"
string.slice!(2) 105
string.slice!(3..6) " is "
string.slice!(/s.*t/) "sa st"
string.slice!("r") "r"
string "thing"

split str.split( pattern=$;, [ limit ] ) -> anArray

Divides str into substrings based on a delimiter, returning an array of these substrings.

If pattern is a String, then its contents are used as the delimiter when splitting str. If pattern is a single space, str is split on whitespace, with leading whitespace and runs of contiguous whitespace characters ignored.

If pattern is a Regexp, str is divided where the pattern matches. Whenever the pattern matches a zero-length string, str is split into individual characters.

If pattern is omitted, the value of $; is used. If $; is nil (which is the default), str is split on whitespace as if `[visible space]' were specified.

If the limit parameter is omitted, trailing null fields are supressed. If limit is a positive number, at most that number of fields will be returned (if limit is 1, the entire string is returned as the only entry in an array). If negative, there is no limit to the number of fields returned, and trailing null fields are not supressed.

" now's  the time".split ["now's", "the", "time"]
" now's  the time".split(' ') ["now's", "the", "time"]
" now's  the time".split(/ /) ["", "now's", "", "the", "time"]
"1, 2.34,56, 7".split(/,\s*/) ["1", "2.34", "56", "7"]
"hello".split(//) ["h", "e", "l", "l", "o"]
"hello".split(//, 3) ["h", "e", "llo"]
"hi mom".split(/\s*/) ["h", "i", "m", "o", "m"]

"mellow yellow".split("ello") ["m", "w y", "w"]
"1,2,,3,4,,".split(',') ["1", "2", "", "3", "4"]
"1,2,,3,4,,".split(',', 4) ["1", "2", "", "3,4,,"]
"1,2,,3,4,,".split(',', -4) ["1", "2", "", "3", "4", "", ""]

squeeze str.squeeze( [ aString ]* ) -> aNewString

Builds a set of characters from the aString parameter(s) using the procedure described for String#count on page 368. Returns a new string where runs of the same character that occur in this set are replaced by a single character. If no arguments are given, all runs of identical characters are replaced by a single character.

"yellow moon".squeeze "yelow mon"
"  now   is  the".squeeze(" ") " now is the"
"putters shoot balls".squeeze("m-z") "puters shot balls"

squeeze! str.squeeze!( [ aString ]* ) -> str or nil

Squeezes str in place, returning either str, or nil if no changes were made.
strip str.strip -> aString

Returns a copy of str with leading and trailing whitespace removed.

"    hello    ".strip "hello"
"\tgoodbye\r\n".strip "goodbye"

strip! str.strip! -> str or nil

Removes leading and trailing whitespace from str. Returns nil if str was not altered.
sub str.sub( pattern, replacement ) -> aString
str.sub( pattern ) {| match | block } -> aString

Returns a copy of str with the first occurrence of pattern replaced with either replacement or the value of the block. If the string form of the method is used, special variables such as $& will not be useful, as substitution into the string occurs before the pattern match starts. However, the sequences \1, \2, listed in Table 22.7 on page 371 may be used.

In the block form, the current match is passed in as a parameter, and variables such as $1, $2, $`, $&, and $' will be set appropriately. The value returned by the block will be substituted for the match on each call.

"hello".sub(/[aeiou]/, '*') "h*llo"
"hello".sub(/([aeiou])/, '<\1>') "h<e>llo"
"hello".sub('.') {|s| s[0].to_s + ' ' } "104 ello"

sub! str.sub!( pattern, replacement ) -> str or nil
str.sub!( pattern ) {| match | block }

-> str or nil

Performs the substitutions of String#sub in place, returning str, or nil if no substitutions were performed.
succ str.succ -> aString
Returns the successor to str. The successor is calculated by incrementing characters starting from the rightmost alphanumeric (or the rightmost character if there are no alphanumerics) in the string. Incrementing a digit always results in another digit, and incrementing a letter results in another letter of the same case. Incrementing nonalphanumerics uses the underlying character set's collating sequence.

If the increment generates a ``carry,'' the character to the left of it is incremented. This process repeats until there is no carry, adding an additional character if necessary.

"abcd".succ "abce"
"THX1138".succ "THX1139"
"<<koala>>".succ "<<koalb>>"
"1999zzz".succ "2000aaa"
"ZZZ9999".succ "AAAA0000"
"***".succ "**+"

succ! str.succ! -> str

Equivalent to String#succ , but modifies the receiver in place.
sum str.sum( aFixnum=16 ) -> anInteger

Returns a basic n-bit checksum of the characters in str, where n is the optional parameter, defaulting to 16. The result is simply the sum of the binary value of each character in str modulo 2n - 1. This is not a particularly good checksum.

swapcase str.swapcase -> aString

Returns a copy of str with uppercase alphabetic characters converted to lowercase and lowercase characters converted to uppercase.

"Hello".swapcase "hELLO"
"cYbEr_PuNk11".swapcase "CyBeR_pUnK11"

swapcase! str.swapcase! -> str or nil

Equivalent to String#swapcase , but modifies the receiver in place, returning str, or nil if no changes were made.
to_f str.to_f -> aFloat

Returns the result of interpreting leading characters in str as a floating point number. Extraneous characters past the end of a valid number are ignored. If there is not a valid number at the start of str, 0.0 is returned. The method never raises an exception.

"123.45e1".to_f 1234.5
"45.67 degrees".to_f 45.67
"thx1138".to_f 0.0

to_i str.to_i -> anInteger

Returns the result of interpreting leading characters in str as a decimal integer. Extraneous characters past the end of a valid number are ignored. If there is not a valid number at the start of str, 0 is returned. The method never raises an exception.

"12345".to_i 12345
"99 red balloons".to_i 99
"0x0a".to_i 0
"hello".to_i 0

to_s str.to_s -> str

Returns the receiver.

to_str str.to_str -> str

Synonym for String#to_s . to_str is used by methods such as String#concat to convert their arguments to a string. Unlike to_s, which is supported by almost all classes, to_str is normally implemented only by those classes that act like strings. Of the built-in classes, only Exception and String implement to_str.

tr str.tr( fromString, toString ) -> aString

Returns a copy of str with the characters in fromString replaced by the corresponding characters in toString. If toString is shorter than fromString, it is padded with its last character. Both strings may use the c1--c2 notation to denote ranges of characters, and fromString may start with a ^, which denotes all characters except those listed.

"hello".tr('aeiou', '*') "h*ll*"
"hello".tr('^aeiou', '*') "*e**o"
"hello".tr('el', 'ip') "hippo"
"hello".tr('a-y', 'b-z') "ifmmp"

tr! str.tr!( fromString, toString ) -> str or nil

Translates str in place, using the same rules as String#tr . Returns str, or nil if no changes were made.
tr_s str.tr_s( fromString, toString ) -> aString

Processes a copy of str as described under String#tr , then removes duplicate characters in regions that were affected by the translation.

"hello".tr_s('l', 'r') "hero"
"hello".tr_s('el', '*') "h*o"
"hello".tr_s('el', 'hx') "hhxo"

tr_s! str.tr_s!( fromString, toString ) -> str or nil

Performs String#tr_s processing on str in place, returning str, or nil if no changes were made.
unpack str.unpack( format ) -> anArray

Decodes str (which may contain binary data) according to the format string, returning an array of each value extracted. The format string consists of a sequence of single-character directives, summarized in Table 22.8 on page 379. Each directive may be followed by a number, indicating the number of times to repeat with this directive. An asterisk (``*'') will use up all remaining elements. The directives sSiIlL may each be followed by an underscore (``_'') to use the underlying platform's native size for the specified type; otherwise, it uses a platform-independent consistent size. Spaces are ignored in the format string. See also Array#pack on page 286.

Directives for String#unpack
Format Function Returns
A String with trailing nulls and spaces removed. String
a String. String
B Extract bits from each character (msb first). String
b Extract bits from each character (lsb first). String
C Extract a character as an unsigned integer. Fixnum
c Extract a character as an integer. Fixnum
d Treat sizeof(double) characters as a native double. Float
E Treat sizeof(double) characters as a double in little-endian byte order. Float
e Treat sizeof(float) characters as a float in little-endian byte order. Float
f Treat sizeof(float) characters as a native float. Float
G Treat sizeof(double) characters as a double in network byte order. Float
g Treat sizeof(float) characters as a float in network byte order. Float
H Extract hex nibbles from each character (most significant first). String
h Extract hex nibbles from each character (least significant first). String
I Treat sizeof(int) 1 successive characters as an unsigned native integer. Integer
i Treat sizeof(int) 1 successive characters as a signed native integer. Integer
L Treat four1 successive characters as an unsigned native long integer. Integer
l Treat four1 successive characters as a signed native long integer. Integer
M Extract a quoted-printable string. String
m Extract a base64 encoded string. String
N Treat four characters as an unsigned long in network byte order. Fixnum
n Treat two characters as an unsigned short in network byte order. Fixnum
P Treat sizeof(char *) characters as a pointer, and return len characters from the referenced location. String
p Treat sizeof(char *) characters as a pointer to a null-terminated string. String
S Treat two1 successive characters as an unsigned short in native byte order. Fixnum
s Treat two1 successive characters as a signed short in native byte order. Fixnum
U Extract UTF-8 characters as unsigned integers. Integer
u Extract a UU-encoded string. String
V Treat four characters as an unsigned long in little-endian byte order. Fixnum
v Treat two characters as an unsigned short in little-endian byte order. Fixnum
X Skip backward one character. ---
x Skip forward one character. ---
Z String with trailing nulls removed. String
@ Skip to the offset given by the length argument. ---

1 May be modified by appending ``_'' to the directive.

"abc \0\0abc \0\0".unpack('A6Z6') ["abc", "abc "]
"abc \0\0".unpack('a3a3') ["abc", " \000\000"]
"aa".unpack('b8B8') ["10000110", "01100001"]
"aaa".unpack('h2H2c') ["16", "61", 97]
"\xfe\xff\xfe\xff".unpack('sS') [-2, 65534]
"now=20is".unpack('M*') ["now is"]
"whole".unpack('xax2aX2aX1aX2a') ["h", "e", "l", "l", "o"]

upcase str.upcase -> aString

Returns a copy of str with all lowercase letters replaced with their uppercase counterparts. The operation is locale insensitive---only characters ``a'' to ``z'' are affected.

"hEllO".upcase "HELLO"

upcase! str.upcase! -> str or nil

Upcases the contents of str, returning nil if no changes were made.
upto str.upto( aString ) {| s | block } -> str

Iterates through successive values, starting at str and ending at aString inclusive, passing each value in turn to the block. The String#succ method is used to generate each value.

"a8".upto("b6") {|s| print s, ' ' }
for s in "a8".."b6"
  print s, ' '
end
produces:
a8 a9 b0 b1 b2 b3 b4 b5 b6
a8 a9 b0 b1 b2 b3 b4 b5 b6


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