文本（link.txt）内容如下：
http://www.sohu.com/index.html http://www.sohu.com/1.html http://www.sohu.com/2.html http://post.sohu.com/index.html http://mp3.sohu.com/index.html http://www.sohu.com/3.html http://post.sohu.com/2.html
如何使用Linux三剑客得到如下结果：域名的出现次数、域名。 4 www.sohu.com 2 post.sohu.com 1 mp3.sohu.com
# 文本内容 [root@centos7 ~]# cat link.txt http://www.sohu.com/index.html http://www.sohu.com/1.html http://www.sohu.com/2.html http://post.sohu.com/index.html http://mp3.sohu.com/index.html http://www.sohu.com/3.html http://post.sohu.com/2.html # grep 实现 [root@centos7 ~]# grep -o -e "[[:alnum:]]\+.sohu.com" link.txt | sort | uniq -c | sort -nr 4 www.sohu.com 2 post.sohu.com 1 mp3.sohu.com # sed 实现 [root@centos7 ~]# sed -rn 's/.*\/\/([[:alnum:]]+\.sohu\.com).*/\1/p' link.txt | sort | uniq -c | sort -nr 4 www.sohu.com 2 post.sohu.com 1 mp3.sohu.com # awk 实现 [root@centos7 ~]# awk -F "/" '{link[$3]++}END{for(i in link){print link[i],i}}' link.txt | sort -nr 4 www.sohu.com 2 post.sohu.com 1 mp3.sohu.com # cut 实现 [root@centos7 ~]# cut -d"/" -f 3 link.txt | sort | uniq -c | sort -nr 4 www.sohu.com 2 post.sohu.com 1 mp3.sohu.com