mofdan 发表于 2018-8-30 09:09:27

shell多种方法解决一道实用linux运维问题!

  原创作品,允许转载,转载时请务必以超链接形式标明文章 原始出处 、作者信息和本声明。否则将追究法律责任。http://linuxedu.taobao.com
  题目:
  4)已知:/etc/hosts的内容为
  192.168.1.11oldboy11.etiantian.org
  192.168.1.21oldboy21.etiantian.org
  192.168.1.31oldboy31.etiantian.org
  #192.168.1.111oldboy111.etiantian.org
  请用shell脚本实现,怎么才能在输入IP后找到/etc/hosts里对应的唯一的hostname?
  解答:
  法1)脚本过滤法

[*]  # cat judgehost.sh
[*]  #!/bin/bash
[*]  echo "please input ip address:"
[*]  read ip
[*]  [ -n "`grep "$ip " /etc/hosts`" ] && \#注意前面的过滤条件结尾带有空格。
[*]  echo "The hostname is: `grep "$ip " /etc/hosts |awk '{print $2}'`" || \
[*]  echo "The ip is invalid"
  提示:
  1)这是一个grep过滤加条件判断的实现语法:
  2)条件判断语法为[ -n "ddd" ] && echo 1 || echo 0
  3)[ -n "`grep "$ip " /etc/hosts`" ] && \#注意前面的过滤条件结尾带有空格。这里啊,是为了排除下面的重复情况
  192.168.1.11oldboy11.etiantian.org
  192.168.1.111oldboy111.etiantian.org
  ----------------我是每种方法分隔符---------------
  法2)脚本精确匹配法:

[*]  #!/bin/bash
[*]  #author oldboy
[*]  #qq 31333741
[*]  #judge input
[*]  if [ $# -ne 1 ]
[*]  then
[*]  echo "input error!"
[*]  exit 1
[*]  fi
[*]
[*]  flag=0
[*]  exec < /etc/hosts
[*]  while read line
[*]  do
[*]  if [ "$1" = "`echo $line|awk '{print $1}'`" ]
[*]  then
[*]  flag=1
[*]  echo "the $1 's hostname is `echo $line|awk '{print $2}'`"
[*]  break;
[*]  fi
[*]  done
[*]  [ $flag -eq 0 ] && echo " sorrry,not find $1 's hostname!"
[*]
  提示:此题,请大家学习while的用法及设置flag的思路。
执行结果:  # sh oldboy.sh 192.168.1.11
  the 192.168.1.11 's hostname is oldboy11.etiantian.org
  # sh oldboy.sh 192.168.1.21
  the 192.168.1.21 's hostname is oldboy21.etiantian.org
  # sh oldboy.sh 192.168.1.311
  sorrry,not find 192.168.1.311 's hostname!
  ----------------我是每种方法分隔符---------------
  特别提示:下面的方法中使用了awk的不同方法来实现同样的功能,来告诉大家,awk是很强大的
  法3)awk精确匹配:
  准备:
  # tail -4 /etc/hosts
  192.168.1.11oldboy11.etiantian.org
  192.168.1.111oldboy111.etiantian.org
  192.168.1.21oldboy21.etiantian.org
  192.168.1.31oldboy31.etiantian.org
  脚本:

[*]  # cat awkhost1.sh
[*]  awk 'BEGIN {a="'$1'"} {if($1==a) print $2; }' /etc/hosts
  执行结果:
  # sh awkhost1.sh 192.168.1.21
  oldboy21.etiantian.org
  # sh awkhost1.sh 192.168.1.31
  oldboy31.etiantian.org
  # sh awkhost1.sh 192.168.1.11
  oldboy11.etiantian.org
  提示:注意a="'$1'"的用法,$1为命令行传参。awk程序中调用系统变量的方法a="'$1'"。
  ----------------我是每种方法分隔符---------------
  法4)awk精确匹配法

[*]  # cat awkhost2.sh
[*]  awk '{if($1=="'$1'") print $2}' /etc/hosts
  执行结果:
  # awkhost2.sh 192.168.1.11
  oldboy11.etiantian.org
  # awkhost2.sh 192.168.1.21
  oldboy21.etiantian.org
  # awkhost2.sh 192.168.1.311
  ----------------我是每种方法分隔符---------------
  法5)awk过滤法

[*]  # cat awkhost4.sh
[*]  awk '/'"${1} "'/''{print $2}' /etc/hosts
[*]  执行结果:
[*]  # awkhost4.sh 192.168.1.21
[*]  oldboy21.etiantian.org
[*]  # awkhost4.sh 192.168.1.11
[*]  oldboy11.etiantian.org
[*]  # awkhost4.sh 192.168.1.31
[*]  oldboy31.etiantian.org
[*]  提示:除了语法外,这道题有个学问,就是过滤时传参结尾要带个空格,这样才能过滤重复IP的情况
[*]  如:
[*]  192.168.1.11oldboy11.etiantian.org
[*]  192.168.1.111oldboy111.etiantian.org
  ----------------我是每种方法分隔符---------------
  法6)awk过滤法

[*]  # cat awkhost5.sh
[*]  awk '{if($1~/'$1'/) print $2}'/etc/hosts ##如果文件第一列包含命令行第一个参数字符则打印第二列
[*]  执行结果:
[*]  # awkhost5.sh 192.168.1.31
[*]  oldboy31.etiantian.org
[*]  # awkhost5.sh 192.168.1.11
[*]  oldboy11.etiantian.org
[*]  oldboy111.etiantian.org ------>这里有bug了。
[*]  # awkhost5.sh 192.168.1.21
[*]  oldboy21.etiantian.org
[*]  改进下来排除bug:
[*]  # cat awkhost5-1.sh
[*]  awk '{if($1~/'$1' /) print $2}'/etc/hosts ==>用上面加空格的思路不对。
[*]  # cat awkhost5-1.sh
[*]  awk '{if($1~/'$1'$/) print $2}'/etc/hosts #增加一个正则表达式$
[*]  执行结果:
[*]  # awkhost5-1.sh 192.168.1.21
[*]  oldboy21.etiantian.org
[*]  # awkhost5-1.sh 192.168.1.11
[*]  oldboy11.etiantian.org
[*]  # awkhost5-1.sh 192.168.1.31
[*]  oldboy31.etiantian.org
  ----------------我是每种方法分隔符---------------
  法7)awk -v精确匹配法

[*]  命令行测试:
[*]  # awk -v p=192.168.1.21 '$1 == p{print $2}' /etc/hosts
[*]  oldboy21.etiantian.org
[*]  # awk -v p=192.168.1.11 '$1 == p{print $2}' /etc/hosts
[*]  oldboy11.etiantian.org
[*]  # awk -v p=192.168.1.11 '$1 == p {print $2}' /etc/hosts
[*]  oldboy11.etiantian.org
[*]  实际脚本:
[*]  # cat awkhost6.sh
[*]  #!/bin/bash
[*]  #p=$1
[*]  #awk -v p="$p"'$1 == p{print $2}' /etc/hosts
[*]  awk -v p="$1"'$1 == p{print $2}' /etc/hosts
  执行结果:
  # shawkhost6.sh192.168.1.11
  oldboy11.etiantian.org
  # shawkhost6.sh192.168.1.21
  oldboy21.etiantian.org
  提示:
  1)传参非awk程序,因此写法p="$1"
  2)man awk
  -v var=val
  --assign var=val
  Assign the value val to the variable var, before execution of the program begins.   Suchvari-
  able values are available to the BEGIN block of an AWK program.
  ----------------我是每种方法分隔符---------------
  法8:精确匹配简单的写法

[*]  # cat awkhost9.sh
[*]  awk'$1 == "'$1'" {print $2}' /etc/hosts
[*]  执行结果:
[*]  # sh awkhost9.sh192.168.1.11
[*]  oldboy11.etiantian.org
[*]  # sh awkhost9.sh192.168.1.21
[*]  oldbo.org
[*]  # sh awkhost9.sh192.168.1.31
[*]  oldboy31.etiantian.org
[*]  特别提示:这里大量的使用了awk的不同方法来实现同样的功能,很强大吧。
  ----------------我是每种方法分隔符---------------
  法9:一个不成熟的实现法

[*]  #!/bin/bash
[*]  b=/$PWD/wang.txt
[*]  echo -n "plase input ip : "
[*]  read a
[*]  if [ $a == "192.168.1.11" ]
[*]  then
[*]  cat $b | grep $a | awk -F ' ''{print $2}'
[*]
[*]  elif [ $a== "192.168.1.21" ]
[*]  then
[*]  cat $b | grep $a | awk -F ' ''{print $2}'
[*]
[*]  elif [ $a== "192.168.1.31" ]
[*]  then
[*]  cat $b | grep $a | awk -F ' ''{print $2}'
[*]  else
[*]  echo "plase input the correct IP address " && exit 1
[*]  fi
[*]  提示:大家看看问题在哪?脚本不通用。
[*]
  ----------改进后

[*]  #!/bin/bash
[*]  #author oldboy
[*]  #qq 541376442
[*]  hosts_file="$PWD/oldboy.txt"
[*]  #judge file
[*]  [ ! -f $hosts_file ] && echo "no test file!" && exit 1
[*]  echo -n "plase input ip : "
[*]  read ip
[*]  #judge ip format
[*]  [ "${#a}" -lt 8 ] && [ "`echo $ip|sed 's///g'`" != "..." ] && \
[*]  echo "Plase input the correct IP address" && exit 1
[*]
[*]  #start
[*]  result1=$(grep "$ip" $hosts_file|awk '{print $1}')
[*]  if [ "$ip" == "$result1" ]
[*]  then
[*]  grep "$ip" $hosts_file|awk '{print $2}'
[*]  exit 0
[*]  else
[*]  echo"Not find the hostname of $ip"
[*]  exit 1
[*]  fi
[*]  提示:此法不可取,画蛇添足了。


页: [1]
查看完整版本: shell多种方法解决一道实用linux运维问题!