#以大写字母开始后面紧跟N个数字，方式一
reg = /[A-Z]\d+/
#方式二
reg = Regexp.new("[A-Z]\d+")
reg = Regexp.new(/[A-Z]\d+/)

letter_somenum = /[A-Z|a-z]\d+/if letter_somenum =~ "f1"print "f1 matches regexp"
elseprint "f1 not matches regexp"
end

#只要字符串中含有a到z且紧跟数字的都满足
/[a-z]\d+/

#匹配以大写字母开头的表达式
reg = /^[A-Z]/

#匹配末尾是大写字母的字符串
second = Regexp.new("[A-Z]$")
p second =~ "F1"
p second =~ "1F"

#首位匹配，全部是大写字母
third = Regexp.new("^[A-Z]+$")

#ABC三个字符中的任意一个
/[ABC]/

#对于连续的字符可以使用-，匹配任意一个大写字母
/[A-Z]/

#匹配任意字母或下划线
/[A-Za-z_]/

#ABC之外的所有字符
/[^ABC]/

#以V开头，以s结尾的所有字符串
never_mind = /^V.*s$/
p never_mind =~ "Voctrals"

#F开头，N个字母，空格，N个字母结尾
space = /^F[A-Za-z]+\s[A-Za-z]+$/

#匹配多余0个数字
number = /^\d+$/

#匹配三个字母或者数字
letter_num = /^\w\w\w$/

#当且仅当前端匹配成功
front = /\Aabc/

#当且仅当末端匹配成功
back = /abc\Z/

#出现0次A，或者N次A
/A*/

#出现N次A，N不允许为0
/A+/

#要么出现A，要么就不要出现A,*这里好像有个BUG！！！*
/A?/

#匹配最短的A*B，最好就是AAB
/A*?B/
#匹配最短的A?B，最好就是AB
/A+?B/

#匹配重复的ABC
/(ABC)*/

#匹配ABC或者CBA
/(ABC)*|(CBA)*/

/[a-z]*/i

/[a-z]+    #N个字母
\d?    #一个或没有数字
/xi

/(.)(..)(.)/ =~ "why????"p $1    #=>"w"
p $2    #=>"hy"
p $3    #=>"?"

/(.)(\d\d)+(.)/ =~ "123456"
p $1    #=>1
p $2    #=>45
p $3    #=>6
/(.)(?:\d\d)+(.)/ =~ "123456"
p $1    #=>1
p $2    #=>6

/Shift/i =~ "control shift alt table"
p $`    #=>"control "
p $&    #=>"shift"
p $'    #=>" alt table"

some= "abc  def    ghi jk    lmn"
#把第一个匹配的多个空格替换为_
p some.sub(/\s+/, "_")    #=>"abc_def    ghi jk    lmn"
p some    #=>"abc  def    ghi jk    lmn"
#把所有匹配的多个空格替换为_
p some.gsub(/\s+/, "_")    #=>"abc_def_ghi_jk_lmn"
p some    #=>"abc  def    ghi jk    lmn"

some= "abc  def    ghi jk    lmn"
# 替换第一个满足的部分为^_^
matched = some.sub(/\s+/) { |match| "^_^"
}
p matched    #=> "abc^_^def    ghi jk    lmn"

scantest = "This is a string test for scan"
gather = Array.newother = scantest.scan(/i./){|matched|gather.unshift(matched)
}
p gather    #=>["in", "is", "is"]

scantest = "This is a string test for scan"gather = Array.newscantest.scan(/(i)(.)/){|matched|gather.unshift(matched)
}p gather    #=>[["i", "n"], ["i", "s"], ["i", "s"]]

scantest = "This is a string test for scan"gather = Array.newscantest.scan(/(i)(.)/){|a, b|gather.unshift(a)gather.unshift(b)
}p gather    #=>["n", "i", "s", "i", "s", "i"]

scantest = "This is a string test for scan"gather = Array.newgather = scantest.scan(/i./)p gather    #=>["is", "is", "in"]