求助，正则表达式有不懂的地方

fh21_xuejinlian

回复 9# lorihuang/sat(urday)?/和 /sat/ 不是划等号的 /sat(urday)?/ 可以匹配的情况是 satu satr satd sata saty sat六种情况

fh21_xuejinlian

回复 9# lorihuang/sat(urday)?/和 /sat/ 不是划等号的 /sat(urday)?/ 可以匹配的情况是 satu satr satd sata saty sat六种情况

lorihuang

回复 12# fh21_xuejinlian
对对对！还是思维不够严谨！总有想不到的地方！真的是来对论坛了，没想到提问的当天就能解决！

jason680

回复 1# lorihuang

/b[ae]?t/   
1. [ae] => a or e
2. [ ]?  => [] or "" (empty)
3. b[ae]?t => b[ae]t or bt => bat or bet or bt

/b[ae]+t/
1. []+
   + => 1 or more
   []+ => [] or [][] or [][][] or [][][]...[]
2.  b[ae]+t
   + = 1, []+ = [] ,   b[ae]t => bat or bet
   + = 2, []+ = [][], b[ae][ae]t => baat or baet or beat or beet
   + = 3, []+ = [][][], b[ae][ae][ae]t => baaat or baaet or .... beet
   + = N, []+ = [][][]...[], baaa....at or ... or beee...et



/b[ae]{1,2}t/
1.  []{1,2} => [] or [][]
2. b[ae]{1,2}t
   []{1} = [] ,   b[ae]t => bat or bet
   []{2} = [][], b[ae][ae]t => baat or baet or beat or beet


最后一个问题，书中说echo "saturday"|gawk '/sat(urday)?/{print $0}'匹配上，我自己尝试分别使用echo “saturday1”、"sat1urday"、"sat1u2rday"都能匹配上

/sat(urday)?/
1. ()? => () or "" (empty)
2. sat(urday)?
  ()? = () , sat(urday)? => saturday
  ()? = ""(empty),   sat(urday)? => sat





后来我修改语句为echo "saturday"|gawk '/sat(urda)?y/{print $0}'时，发现saturday1234也能匹配上，但是当echo “saturda2y”、"sat1urday"、"sat1u2rday"都是无法匹配的，请问为什么？我是哪个地方没有理解透彻？

/sat(urda)?y/
1. ()? = ()
  sat(urda)?y =   saturday
2. ()? = "" (empty)
  sat(urda)?y =   saty

lorihuang

回复 14# jason680

写得好清楚啊！就跟梳理知识点似的！感谢解惑！！！

sditmaner

你说的这些，我还真不会，但是我照样觉得我是脚本牛人

jason680

回复 17# 本友会机友会摄友会

http://bbs.chinaunix.net/thread-4259168-1-1.html