Old boy Education daily-60th day-a practical Linux operation 9 kinds of shell solution Method!

2017-06-04

1. The problem is:

Known: The content of/etc/hosts is

192.168.1.11 oldboy11.etiantian.org192.168.1.21 oldboy21.etiantian.org192.168.1.31 oldboy31.etiantian.org# 192.168.1.111 oldboy111.etiantian.org

Please use shell script to implement, how can I find the corresponding unique hostname in/etc/hosts after entering IP?

2. Solution: Act 1) Script filtering method

[Email protected]_boy scripts]# 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 $} '" | | \ echo "The IP is invalid"

Tips:
1) This is a grep filter plus conditional judgment implementation syntax:
2) The conditional judgment syntax is[ -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. Here, to rule out the following repetition .

192.168.1.11 oldboy11.etiantian.org
192.168.1.111 oldboy111.etiantian.org

------------------I am the delimiter of each method----------------------

Method 2) Script exact matching method:

#!/bin/bash    #author  oldboy    #qq  31333741    #judge  input   if [ $# -ne 1 ]    then      echo  "input error!"      exit 1  fi   flag=0  exec <  /etc/hosts  while read line  do   if [  "$"   =  "' 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! ' 

Hint: This question, please learn the use of while and set the idea of flag.
Execution Result:

[Email protected]_boy scripts]# sh oldboy.sh 192.168.1.11the 192.168.1.11 ' s hostname is oldboy11.etiantian.org [[email P Rotected]_boy scripts]# sh oldboy.sh 192.168.1.21 the 192.168.1.21 ' s hostname is oldboy21.etiantian.org[[email protected ]_boy scripts]# sh oldboy.sh 192.168.1.311sorrry,not find 192.168.1.311 ' s hostname!

----------------I am the delimiter of each method---------------
Special Note: In the following method, the old boy teacher used a lot of different methods of awk to achieve the same function, to tell you that awk is very powerful, I hope students can be proficient in accordance with the teacher's teaching requirements.

Method 3) awk exact match:

Get ready:

[Email protected]_boy scripts]# tail-4/etc/hosts192.168.1.11 oldboy11.etiantian.org192.168.1.111 oldboy111.etiantian.org192.168.1.21 oldboy21.etiantian.org192.168.1.31 oldboy31.etiantian.org

Script:

[[Email Protected]_boy scripts]# cat awkhost1.sh awk ' BEGIN {a= ' ' $ '} {if ($1==a) print $;} '/etc/hosts

Execution Result:

[[Email protected]_boy scripts]# sh awkhost1.sh 192.168.1.21oldboy21.etiantian.org[[email protected]_boy scripts]# sh awkhost1.sh 192.168.1.31oldboy31.etiantian.org[[email protected]_boy scripts]# sh awkhost1.sh 192.168.1.11oldboy11.etiantian.org

Tip: Note the use of a= "' $ '" for command-line arguments. The method of calling system variables in the awk program a= "' $ '".
----------------I am the delimiter of each method---------------

Method 4) Awk exact Match method

[Email protected]_boy scripts]# cat awkhost2.sh awk ' {if ($1== "' $ '") print $ '/etc/hosts

Execution Result:

[Email protected]_boy scripts]# awkhost2.sh 192.168.1.11oldboy11.etiantian.org[[email protected]_boy scripts]# awkhost2.sh 192.168.1.21oldboy21.etiantian.org[[email protected]_boy scripts]# awkhost2.sh 192.168.1.311

----------------I am the delimiter of each method---------------

Method 5) Awk Filter method

[[Email Protected]_boy scripts]# cat awkhost4.sh awk '/' ' ${1} '/' ' {print $} '/etc/hosts

Execution Result:

[Email protected]_boy scripts]# awkhost4.sh 192.168.1.21 oldboy21.etiantian.org [[Email Protected]_boy scripts]# awkho st4.sh 192.168.1.11 oldboy11.etiantian.org [[email protected]_boy scripts]# awkhost4.sh 192.168.1.31 Oldboy31.etiantia n.org

Hint: In addition to the syntax, this problem has a knowledge, is to filter the end of the simultaneous to take a space, so as to filter the case of duplicate IP

such as:

192.168.1.11 oldboy11.etiantian.org 192.168.1.111 oldboy111.etiantian.org "---------------- I am the delimiter of each method---------------# # #法6) awk filter "' Bash[[email protected]_boy scripts]# cat awkhost5.sh awk ' {if ($1~/' $ '/) print $ '/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

Execution Result:

[Email protected]_boy scripts]# awkhost5.sh 192.168.1.31 oldboy31.etiantian.org [[Email Protected]_boy scripts]# awkho  st5.sh 192.168.1.11 oldboy11.etiantian.org oldboy111.etiantian.org------> There's a bug here. [Email protected]_boy scripts]# awkhost5.sh 192.168.1.21 oldboy21.etiantian.org

Improved to exclude bugs:

[[Email Protected]_boy scripts]# cat awkhost5-1.sh awk ' {if ($1~/' $ '/) print $ '/etc/hosts ==> the idea of adding a space above is incorrect. [[Email Protected]_boy scripts]# cat awkhost5-1.sh awk ' {if ($1~/' $ ' $/) print $ '/etc/hosts #增加一个正则表达式 $

Execution Result:

[Email protected]_boy scripts]# awkhost5-1.sh 192.168.1.21 oldboy21.etiantian.org [[Email Protected]_boy scripts]# awk host5-1.sh 192.168.1.11 oldboy11.etiantian.org [[email protected]_boy scripts]# awkhost5-1.sh 192.168.1.31 oldboy31.et iantian.org

----------------I am the delimiter of each method---------------

Method 7) Awk-v exact matching method

Command-line testing:

[Email protected]_boy scripts]# awk-v p=192.168.1.21 ' = = p{print $} '/etc/hosts oldboy21.etiantian.org [email Pro  Tected]_boy scripts]# awk-v p=192.168.1.11 ' $ = = P{print $} '/etc/hosts oldboy11.etiantian.org [[Email Protected]_boy scripts]# awk-v p=192.168.1.11 ' = = = p {print $} '/etc/hosts oldboy11.etiantian.org

Actual script:

[Email protected]_boy scripts]# cat awkhost6.sh #!/bin/bash #p =$1 #awk-v p= "$p" ' = = P{print $} '/etc/hosts a Wk-v p= "$" ' $ = = P{print '/etc/hosts

Execution Result:

[[Email protected]_boy scripts]# sh awkhost6.sh 192.168.1.11oldboy11.etiantian.org[[email protected]_boy scripts]# sh A Wkhost6.sh 192.168.1.21oldboy21.etiantian.org

Tips:
1) Pass the non-awk program, so the wording p= "$"
2) Man awk
- v Var=val
--assign Var=val
Assign The value Val to the variable Var, before execution of the program begins. Such vari-
able values is available to the BEGIN block of a AWK program.
----------------I am the delimiter of each method---------------

Method 8: Exact match simple notation

[Email protected]_boy scripts]# cat awkhost9.sh awk ' $ = ' ' $ ' "{print $} '/etc/hosts

Execution Result:

[Email protected]_boy scripts]# sh awkhost9.sh 192.168.1.11 oldboy11.etiantian.org [[Email protected]_boy scripts]# SH awkhost9.sh 192.168.1.21 oldboy21.etiantian.org [[email protected]_boy scripts]# sh awkhost9.sh 192.168.1.31 oldboy3 1.etiantian.org

Special Note: Here the old boy teacher a lot of use of awk different methods to achieve the same function, very powerful,

I hope that students can be proficient in accordance with the teacher's teaching requirements.
----------------I am the delimiter of each method---------------

Law 9: An immature realization of the students

#!/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  " &&AMp; exit 1  fi 

Tip: Let's see where the problem is. Scripts are not generic.

----------old boy teacher improved after

#!/bin/bash    #author  oldboy    #qq  31333741   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  $ip |sed  ' s/[0-9]//g"  !=  "..."  ]  && \  echo  "Plase input the correct ip address"   && exit 1   #start    result1=$ (grep  "$ip"   $hosts _file|awk   ' {print $1} ')    if [  "$ip"  ==  "$result 1"  ]    then           grep  "$iP "  $hosts _file|awk  ' {print $2} '          exit  0  else         echo   "Not find the  hostname of  $ip "         exit 1    fi

Hint: This method is not advisable, superfluous.

This article is from the "Lee blog" blog, make sure to keep this source http://lidao.blog.51cto.com/3388056/1932142

Old boy Education daily-60th day-a practical Linux operation 9 kinds of shell solution Method!