shell编程面试必会30题

来源说明：《跟老男孩学Linux运维》Shell编程实战

说明:对于每个脚本，用shell编程的同时，我再用python实现，达到同时熟悉两种脚本语言的目的。由于初学python，有问题还请大家斧正。

面试题1：批量生产随机字符文件名

用shell实现

代码：

root@vmUbu:/home/dell/shell# vim creat_ten_htmlfile.sh 
#!/bin/bash

#Date: 2017-8-25
#Author: XianWei

Path=/tmp/shelltmp
[ -d "$Path" ] || mkdir -p $Path                #如果测试结果为假，就执行mkdir语句
cd $Path
for((i=0;i<10;i++))                             #循环执行10次
do
        namepre=`date +%s|md5sum|tr -dc "a-z"`  #生成随机的10个字母
        namepost='_oldboy.html'                 #文件名的后缀
        filename=${namepre}${namepost}          #字符串连接
        touch $filename
        echo "$filename have been created."
        sleep 1

done &
wait

测试

root@vmUbu:/home/dell/shell# ./creat_ten_htmlfile.sh 
adcaeeafbc_oldboy.html have been created.
ecbdeabdaedceb_oldboy.html have been created.
edffdbddee_oldboy.html have been created.
beadcabbbdcbdb_oldboy.html have been created.
fcaadeaedafbc_oldboy.html have been created.
adddadbc_oldboy.html have been created.
bcadafebdabe_oldboy.html have been created.
deffebcd_oldboy.html have been created.
fafbbcdcfcfecef_oldboy.html have been created.
fbfdedccbcc_oldboy.html have been created.
root@vmUbu:/home/dell/shell# 
root@vmUbu:/home/dell/shell# ll /tmp/shelltmp/
total 8
drwxr-xr-x  2 root root 4096 Aug 25 07:53 ./
drwxrwxrwt 15 root root 4096 Aug 25 08:05 ../
-rw-r--r--  1 root root    0 Aug 25 07:53 adcaeeafbc_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 07:53 adddadbc_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 07:53 bcadafebdabe_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 07:53 beadcabbbdcbdb_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 07:53 deffebcd_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 07:53 ecbdeabdaedceb_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 07:53 edffdbddee_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 07:53 fafbbcdcfcfecef_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 07:53 fbfdedccbcc_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 07:53 fcaadeaedafbc_oldboy.html

总结：

考察知识点：

1）生成随机数的方法

2）字符串连接的方法

使用Python实现

代码

#encoding:utf-8

import random
import os

def get10char():                                        #create 10 random charactors
  seed = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
  sa = []
  for i in xrange(10):
    sa.append(random.choice(seed))
  salt = ''.join(sa)

  return salt

def createfile(name):
  path="/tmp/shelltmp/"                                 #check whether the dir is exists,if not create it
  if os.path.exists(path) != True:
    os.mkdir(path)

  pathAndName=path+name
  with open(pathAndName,"wb") as f:                     #create file
    pass
  if os.path.exists(pathAndName):
    print "%s have been created" %name                  #print the result
  else:
    print "create file failed,Please check it."


def main():
  for i in xrange(10):                                  #loop 10 times to create 10 file
    filename=get10char()+"_oldboy.html"
    createfile(filename)


if __name__ == "__main__":
        main()

面试题2：将面试题1中的字符串oldboy全部改为oldgirl

方法一:使用awk生成所需命令，再用bash执行

代码和测试：

root@vmUbu:/tmp/shelltmp# for i in `ls /tmp/shelltmp`;do echo $i|awk -F "_" '{print "mv " $0 " " $1"_oldgirl.html" }' |bash ;done

root@vmUbu:/tmp/shelltmp# ls
adcaeeafbc_oldgirl.html    beadcabbbdcbdb_oldgirl.html  edffdbddee_oldgirl.html       fcaadeaedafbc_oldgirl.html
adddadbc_oldgirl.html      deffebcd_oldgirl.html        fafbbcdcfcfecef_oldgirl.html
bcadafebdabe_oldgirl.html  ecbdeabdaedceb_oldgirl.html  fbfdedccbcc_oldgirl.html
root@vmUbu:/tmp/shelltmp#

方法2：使用sed替换文件名，再用mv修改文件名

代码

#!/bin/bash

#Date: 2017-8-25
#Author: XianWei

Path=/tmp/shelltmp
[ -d "$Path" ] || exit 0                #如果测试结果为假，就执行mkdir语句
cd $Path

for oldfile in `ls $Path/ |grep oldboy`
do
        newfile=`echo $oldfile | sed s/oldboy/oldgirl/g` #生成新的文件名
        mv $oldfile $newfile

done &
wait

测试

root@vmUbu:/home/dell/shell# python 1_creat_ten_htmlfile.py 
WKfqYfUprf_oldboy.html have been created
QplbhAZVZA_oldboy.html have been created
jmkkmepTfD_oldboy.html have been created
IAeFZLHzOj_oldboy.html have been created
DwWbMsCqtN_oldboy.html have been created
ZgAVXNCyLQ_oldboy.html have been created
DBENsfnZpv_oldboy.html have been created
PveegnMyBo_oldboy.html have been created
MpReSrwXJr_oldboy.html have been created
SWWFrkYhdi_oldboy.html have been created
root@vmUbu:/home/dell/shell# 
root@vmUbu:/home/dell/shell# ll /tmp/shelltmp/              
total 8
drwxr-xr-x  2 root root 4096 Aug 25 11:32 ./
drwxrwxrwt 16 root root 4096 Aug 25 11:32 ../
-rw-r--r--  1 root root    0 Aug 25 11:32 DBENsfnZpv_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 11:32 DwWbMsCqtN_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 11:32 IAeFZLHzOj_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 11:32 jmkkmepTfD_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 11:32 MpReSrwXJr_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 11:32 PveegnMyBo_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 11:32 QplbhAZVZA_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 11:32 SWWFrkYhdi_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 11:32 WKfqYfUprf_oldboy.html
-rw-r--r--  1 root root    0 Aug 25 11:32 ZgAVXNCyLQ_oldboy.html
root@vmUbu:/home/dell/shell#

python实现

代码

#encoding:utf-8

import random
import os
import sys


def main():
  path="/tmp/shelltmp/"
  if os.path.exists(path) !=True:                               #check the dir whether exists
    print "%s not exists,check it." %path
    sys.exit(1)

  for root,dir,file in os.walk(path):                           #put the dest file into a list
    pass
  for oldfilename in file:
    if oldfilename.split("_")[1] == "oldboy.html":              #if filename include strings "oldboy",change its name
      newfilename = oldfilename.split("_")[0]+"_oldgirl.html"   
      os.rename(path+oldfilename,path+newfilename)              #change name
      if os.path.exists(path+newfilename):                      #print the result 
        print "%s have been change name to %s" %(oldfilename,newfilename)
      else:
        print "%s changed name failed." %(oldfilename)


if __name__ == "__main__":
        main()

测试

root@vmUbu:/home/dell/shell# ls /tmp/shelltmp/
COFoqgRped_oldboy.html  FnlInKOFDD_oldboy.html  KraoAAesrC_oldboy.html  LFCkswpeJc_oldboy.html  RXwWPTAYTF_oldboy.html
dxTHbQyYyZ_oldboy.html  ickDGJUVgD_oldboy.html  LBbLaTnuRW_oldboy.html  ReFkjxYZjO_oldboy.html  tKwmVefsCP_oldboy.html
root@vmUbu:/home/dell/shell# python 2_change_name.py        
LFCkswpeJc_oldboy.html have been change name to LFCkswpeJc_oldgirl.html
dxTHbQyYyZ_oldboy.html have been change name to dxTHbQyYyZ_oldgirl.html
FnlInKOFDD_oldboy.html have been change name to FnlInKOFDD_oldgirl.html
RXwWPTAYTF_oldboy.html have been change name to RXwWPTAYTF_oldgirl.html
COFoqgRped_oldboy.html have been change name to COFoqgRped_oldgirl.html
ReFkjxYZjO_oldboy.html have been change name to ReFkjxYZjO_oldgirl.html
LBbLaTnuRW_oldboy.html have been change name to LBbLaTnuRW_oldgirl.html
tKwmVefsCP_oldboy.html have been change name to tKwmVefsCP_oldgirl.html
KraoAAesrC_oldboy.html have been change name to KraoAAesrC_oldgirl.html
ickDGJUVgD_oldboy.html have been change name to ickDGJUVgD_oldgirl.html
root@vmUbu:/home/dell/shell# ls /tmp/shelltmp/       
COFoqgRped_oldgirl.html  FnlInKOFDD_oldgirl.html  KraoAAesrC_oldgirl.html  LFCkswpeJc_oldgirl.html  RXwWPTAYTF_oldgirl.html
dxTHbQyYyZ_oldgirl.html  ickDGJUVgD_oldgirl.html  LBbLaTnuRW_oldgirl.html  ReFkjxYZjO_oldgirl.html  tKwmVefsCP_oldgirl.html
root@vmUbu:/home/dell/shell#

面试题3：批量创建用户和密码

代码

root@vmUbu:/home/dell/shell# vim 3_create_user.sh 
 
#!/bin/bash

#Date: 2017-8-25
#Author: XianWei
#create ten users in bulk


for((i=0;i<=10;i++))
do
        username="oldboy${i}"                           #cannot use symbol ''
        password=`tr -dc "a-zA-Z0-9" > passwd.txt    #record the username and it's password
done

测试

root@vmUbu:/home/dell/shell# ./3_create_user.sh 
root@vmUbu:/home/dell/shell# cat /etc/passwd
......
hello:x:1001:1001::/home/hello:
oldboy0:x:1002:1002::/home/oldboy0:
oldboy1:x:1003:1003::/home/oldboy1:
oldboy2:x:1004:1004::/home/oldboy2:
oldboy3:x:1005:1005::/home/oldboy3:
oldboy4:x:1006:1006::/home/oldboy4:
oldboy5:x:1007:1007::/home/oldboy5:
oldboy6:x:1008:1008::/home/oldboy6:
oldboy7:x:1009:1009::/home/oldboy7:
oldboy8:x:1010:1010::/home/oldboy8:
oldboy9:x:1011:1011::/home/oldboy9:
oldboy10:x:1012:1012::/home/oldboy10:
root@vmUbu:/home/dell/shell# 

#查看密码文件
root@vmUbu:/home/dell/shell# cat passwd.txt 
oldboy0 Je28ZqTi
oldboy1 LcA5AX3u
oldboy2 QF36POh2
oldboy3 5BMoklFp
oldboy4 18slv8fB
oldboy5 8eIVWck3
oldboy6 ZuWQcqjT
oldboy7 lSeahDHM
oldboy8 XvqBiFPA
oldboy9 VNc8fLZC
oldboy10 zdbruc2S

python实现

代码

#encoding:utf-8

'''
#date: 2017-8-26
#Author: XianWei from ChengDu
#scripte Function: create users and set its password in bulk
'''
import random
import os
import sys
import subprocess
import random

def get_passwd(n):
    passwdlist=[]
    seed="abcdefghijkmnopqrstuvwxyz"
    for j in xrange(n):
        passwdlist.append(random.choice(seed))
    passwd = "".join(passwdlist)
    return passwd

def create_user(user):
        create_user_cmd = 'useradd %s ' %user
        p = subprocess.Popen(args=create_user_cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, close_fds=True)
        returncode = p.wait()
        if returncode == 0:
            print "useradd %s succussful" %user
            password=get_passwd(8)
            set_passwd_cmd = 'echo %s:%s |chpasswd' %(user,password)
            p2 = subprocess.Popen(args=set_passwd_cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, close_fds=True)
            returncode_p2 = p2.wait()
            if returncode_p2 == 0:
                print "%s set password succussful.its password : %s" %(user,password)
            else:
                print "sorry,set password failed!"
        else:
            print "useradd failed."
            sys.exit(1)

def main():
    userlist = []
    for i in xrange(1,11):
        userlist.append("oldgirl"+str(i))
    for user in userlist:
        create_user(user)


if __name__ == "__main__":
        main()

测试

root@vmUbu:/home/dell/shell# python 3_create_user.py                                     useradd oldgirl1 succussful
oldgirl1 set password succussful.its password : qtcvheyq
useradd oldgirl2 succussful
oldgirl2 set password succussful.its password : wnaecfxu
useradd oldgirl3 succussful
oldgirl3 set password succussful.its password : wpxwtcvv
useradd oldgirl4 succussful
oldgirl4 set password succussful.its password : cpquxwzd
useradd oldgirl5 succussful
  dgirl5 set password succussful.its password : gdtmttug
useradd oldgirl6 succussful
oldgirl6 set password succussful.its password : eznjdjow
useradd oldgirl7 succussful
oldgirl7 set password succussful.its password : eysxegpu
useradd oldgirl8 succussful
oldgirl8 set password succussful.its password : yhdkrdyb
useradd oldgirl9 succussful
oldgirl9 set password succussful.its password : omytwhdh
useradd oldgirl10 succussful
oldgirl10 set password succussful.its password : zpenokqg
root@vmUbu:/home/dell/shell# 
root@vmUbu:/home/dell/shell#  cat /etc/passwd |grep oldgirl
oldgirl1:x:1013:1013::/home/oldgirl1:
oldgirl2:x:1014:1014::/home/oldgirl2:
oldgirl3:x:1015:1015::/home/oldgirl3:
oldgirl4:x:1016:1016::/home/oldgirl4:
oldgirl5:x:1017:1017::/home/oldgirl5:
oldgirl6:x:1018:1018::/home/oldgirl6:
oldgirl7:x:1019:1019::/home/oldgirl7:
oldgirl8:x:1020:1020::/home/oldgirl8:
oldgirl9:x:1021:1021::/home/oldgirl9:
oldgirl10:x:1022:1022::/home/oldgirl10:
root@vmUbu:/home/dell/shell#

面试题4：扫描网络内存活主机

代码

#!/bin/bash

#Date: 2017-8-26
#Author: XianWei
#check the server whether is alive

ippre='192.168.142.'
cmd='ping -c2 '

for((i=0;i<=20;i++))
do
{
        $cmd $ippre$i > /dev/null 2&>1
        if [ $? -eq 0 ]
        then
                echo "$ippre$i  is ok"
        else
                echo "$ippre$i  is down"
        fi
}&                                              #parallel progress
done
wait                                            #let parent progress wait all child progress

测试

root@vmUbu:/home/dell/shell# time ./4_ping_host.sh 
192.168.142.0  is down
192.168.142.2   is ok
192.168.142.11  is down
192.168.142.20  is down
192.168.142.4  is down
192.168.142.12  is down
192.168.142.3  is down
192.168.142.9  is down
192.168.142.18  is down
192.168.142.5  is down
192.168.142.15  is down
192.168.142.13  is down
192.168.142.16  is down
192.168.142.17  is down
192.168.142.10  is down
192.168.142.14  is down
192.168.142.6  is down
192.168.142.19  is down
192.168.142.1  is down
192.168.142.7  is down
192.168.142.8  is down

real    0m11.229s
user    0m0.024s
sys     0m0.720s

python实现

代码

# encoding:utf-8

'''
#date: 2017-8-26
#Author: XianWei from ChengDu
#scripte Function: check ip whether is alived in bulk
'''
import random
import os
import sys
import subprocess
import random
import platform
import re
from threading import Thread
from Queue import Queue
import time


def check_ip(ipaddr):
    #函数用于检测IP地址合法性。来源：http://blog.csdn.net/jbxue123/article/details/23156011
    addr=ipaddr.strip().split('.') #切割IP地址为一个列表
    #print addr
    if len(addr) != 4:              #切割后列表必须有4个参数
        print "%s,ip address is illegal!" %ipaddr
        return False
    for i in range(4):
        try:
            addr[i]=int(addr[i]) #每个参数必须为数字，否则校验失败
        except:
            print "%s,ip address is illegal!" % ipaddr
            return False
        if addr[i]<=255 and addr[i]>=0: #每个参数值必须在0-255之间
            pass
        else:
            print "%s,ip address is illegal!" % ipaddr
            return False
    #print "check ip address success!"
    return True


def ping_host(ip):
    if check_ip(ip) == False:               #检测IP合法性
        sys.exit(1)
    platformOfSystem = platform.system()    #根据平台，设置ping命令
    if (platformOfSystem == "Windows"):
        cmd = "ping -n 2 %s" % (ip)
    if (platformOfSystem == "Linux"):
        cmd = "ping -c 2 %s" % (ip)

    res = os.popen(cmd)


    if (platform.system() == "Windows"):
        if (re.findall("Lost = 2", res.read()).__len__() != 0):
            print "%s  is down." % ip
        else:
            print "%s  is OK." % ip

    if (platform.system() == "Linux"):
        pingResult = re.findall("Destination Host Unreachable", res.read())
        if (pingResult.__len__() != 0):
            print "%s  is down." % ip
        else:
            print "%s  is OK." % ip

def main():

    print "main threading waiting......"
    ip_prefix = "192.168.142."                          #设置ip列表
    iplist = []
    n = 10
    for i in xrange(1,n + 1):
        iplist.append(ip_prefix + str(i))

    tlist = []
    for i in xrange(len(iplist)):                       #使用多线程ping
        t = Thread(target=ping_host, args=(iplist[i],)) #将线程加入list
        tlist.append(t)

    for thread in tlist:                                #启动所有线程
        thread.setDaemon(True)
        thread.start()

    for thread in tlist:                                #等待所有线程结束
        thread.join()

    print "main threading Done"


if __name__ == "__main__":
    main()

linux平台测试

root@vmUbu:/home/dell/shell# time python 4_ping_host.py 
main threading waiting......
192.168.142.1  is OK.
192.168.142.2  is OK.
192.168.142.3  is down.
192.168.142.6  is down.
192.168.142.4  is down.
192.168.142.5  is down.
192.168.142.7  is down.
 192.168.142.8  is down.
192.168.142.9  is down.
192.168.142.10  is down.
main threading Done

real    0m3.166s
user    0m0.100s
sys     0m0.296s
root@vmUbu:/home/dell/shell#

windows平台测试

C:\Users\Administrator\PycharmProjects\shell_to_python\0826>python changename.py

main threading waiting......
192.168.142.1  is OK.
192.168.142.3  is down.
192.168.142.6  is down.
192.168.142.9  is down.
 192.168.142.4  is down.
192.168.142.7  is down.
192.168.142.8  is down.
 192.168.142.5  is down.
192.168.142.2  is OK.192.168.142.10  is down.

main threading Done

面试题10：比较两个数大小

要求：输入两个数，比较大小并输出结果

代码

#!/bin/bash

#Date: 2017-8-27
#Author: XianWei
#作用:输入两个数，比较大小并输出结果


#判断输入的是否为数字
function judgenum()
{
	if [ $1 -gt -99999999 ] > /dev/null 2>&1	#与一个很小的数比较
	then
		echo -n
	else
		echo "Error,Please input a number"
		exit
	fi
}

read -p "Please input the first number:" num1
judgenum $num1
read -p "Please input the second number:" num2
judgenum $num2

let res=$num1-$num2
echo $res

[ $res -gt 0 ] && echo "$num1 > $num2"	
[ $res -lt 0 ] && echo "$num1 < $num2"	
[ $res -eq 0 ] && echo "$num1 = $num2"	

测试

dell@vmUbu:~/shell$ bash judgenum.sh 
Please input the first number:1
Please input the second number:b
Error,Please input a number
dell@vmUbu:~/shell$ bash judgenum.sh  
Please input the first number:a
Error,Please input a number
dell@vmUbu:~/shell$ 
dell@vmUbu:~/shell$ 
dell@vmUbu:~/shell$ 
dell@vmUbu:~/shell$ bash judgenum.sh  
Please input the first number:2
Please input the second number:2
2 = 2
dell@vmUbu:~/shell$ bash judgenum.sh 
Please input the first number:2
Please input the second number:3
2 < 3
dell@vmUbu:~/shell$ bash judgenum.sh 
Please input the first number:2
Please input the second number:1
2 > 1
dell@vmUbu:~/shell$

知识点

    1）如何判断输入的是一个整数。除了本例中的方法还可以使用expr,比如expr num + 1,如果返回值$?为0表示输入的是一个数。否则不是一个数，返回错误并退出

使用Python实现

代码

# encoding:utf-8

import sys

num1 = raw_input()
try:
    num1 = int(num1)
except:
    print "Error ,please input a number."
    sys.exit(2)


num2 = raw_input()
try:
    num2 = int(num2)
except:
    print "Error ,please input a number."
    sys.exit(2)


if(num1>num2):
    print "%d>%d" %(num1,num2)
else:
    if(num1 
  

 
  
未完待续.......