正则表达式的一些用法例子
1. 提取网址的base address
$ url="http://www.flickr.com/search/?q=linux" $ echo $url | egrep -o "https?://[a-z.]+" http://www.flickr.com $ echo $url | egrep -o "https?://[a-z\.]+" http://www.flickr.comdot （点）在 [] 里面不再表示任意一个字符，而是表示点本身。
2. 对网页里面的演员列表排序：
$ lynx -dump http://www.johntorres.net/BoxOfficefemaleList.html | grep -o "Rank-.*" | sed 's/Rank-//; s/\[[0-9]\+\]//' | sort -nk 1 1 Keira Knightley 2 Natalie Portman 3 Monica Bellucci 4 Bonnie Hunt 5 Cameron Diaz 6 Annie Potts 7 Liv Tyler 8 Julie Andrews 9 Lindsay Lohan 10 Catherine Zeta-Jones 11 Cate Blanchett 12 Sarah Michelle Gellar 13 Carrie Fisher 14 Shannon Elizabeth 15 Julia Roberts 16 Sally Field 17 Téa Leoni 18 Kirsten Dunst 19 Rene Russo 20 Jada Pinkett 21 Helen Hunt 22 Halle Berry 23 Kate Winslet 24 Margot Kidder 25 Elizabeth Perkins 26 Lucy Liu 27 Geena Davis 28 Rosie O'Donnell 29 Drew Barrymore 30 Sandra Bullock 31 Tia Carrere 32 Julia Stiles 33 Jane Fonda 34 Renée Zellweger 35 Demi Moore 36 Kathy Bates 37 Kate Beckinsale 38 Lea Thompson 39 Talia Shire 40 Queen Latifah 41 Denise Richards 42 Glenn Close 43 Meg Ryan 44 Whoopi Goldberg 45 Nicole Kidman 46 Jennifer Lopez 47 Jennifer Love Hewitt 48 Laura Dern 49 Mary Elizabeth Mastrantonio 50 Jennifer Aniston 51 Alicia Silverstone 52 Laura Linney 53 Elizabeth Hurley 54 Ashley Judd 55 Michelle Pfeiffer 56 Bette Midler 57 Diane Keaton 58 Sigourney Weaver 59 Jennifer Tilly 60 Jodie Foster 61 Courteney Cox 62 Angelina Jolie 63 Neve Campbell 64 Meryl Streep 65 Julianne Moore 66 Goldie Hawn 67 Linda Hamilton 68 Elisabeth Shue 69 Tara Reid 70 Kim Basinger 71 Annette Bening 72 Kristin Scott Thomas 73 Jeanne Tripplehorn 74 Rachel Weisz 75 Gwyneth Paltrow 76 Teri Garr 77 Jamie Lee Curtis 78 Nia Long 79 Madonna 80 Madeleine Stowe 81 Angela Bassett 82 Reese Witherspoon 83 Selma Blair 84 Kirstie Alley 85 Kathleen Quinlan 86 Susan Sarandon 87 Salma Hayek 88 Debra Winger 89 Winona Ryder 90 Charlize Theron 91 Valeria Golino 92 Sharon Stone 93 Jami Gertz 94 Christina Ricci 95 Marisa Tomei 96 Uma Thurman 97 Diane Lane 98 Jennifer Connelly 99 Nancy Travis 100 Heather Graham 101 Sophie Marceau 102 Jessica Lange 103 Kate Hudson 104 Andie MacDowell 105 Naomi Watts 106 Jennifer Jason Leigh上面的命令也可以写成：
lynx -dump http://www.johntorres.net/BoxOfficefemaleList.html | grep -o "Rank-.*" | sed 's/Rank-//; s/[[0-9]\+]//' | sort -nk 1
3. 提取网页里面的title 信息:
$ echo "<title>Taiwan becomes the third Chinese special administration area following Hongkong and Macau</title><title>Chinese forces destroy Japan's most powerful fleet in South Pacific</title>" | > sed 's:</title>:&\n:' | sed 's:.*<title>\([^<]*\).*:\1:' Taiwan becomes the third Chinese special administration area following Hongkong and Macau Chinese forces destroy Japan's most powerful fleet in South Pacific
后面的 sed 里面的 \([^<]\)* 不能改成 \([^<]\).*
4. 提取 IP地址：
$ ifconfig wlan0 | egrep -o "inet addr:[^ ]*" | grep -o "[0-9.]*" 192.168.1.3