第18章.控制流结构

1.简单的if语句

[root@test zwc]# cat iftest

#!/bin/sh

#iftest

if [ "10" -lt "12" ]

then echo "Yes, 10 is less than 12"

fi

[root@test zwc]# ls -l iftest

-rw-r--r--  1 root root 78  9月 20 02:04 iftest

[root@test zwc]# chmod 750 iftest

[root@test zwc]# ./iftest

Yes, 10 is less than 12

2.测试变量值

[root@test zwc]# cat iftest2

#!/bin/sh

#if test2

echo -n "Enter your name :"

read NAME

if [ "$NAME" = "" ] ; then

echo "You did not enter any information"

 

[root@test zwc]# chmod 750 iftest2

[root@test zwc]# ./iftest2

Enter your name :

You did not enter any information

[root@test zwc]# ./iftest2

Enter your name :zwc

11.变量设置测试

[root@test zwc]# cat ifeditor

#!/bin/sh

#ifeditor

if [ -z $EDITOR ]; then

#the variable hao not been set

 echo "Your EDITOR envitonment is not set"

else

#let's see what it is

 echo "Using $EDITOR as the default editor"

fi

[root@test zwc]# chmod 750 ifeditor

[root@test zwc]# ./ifeditor

Your EDITOR envitonment is not set

12.检测运行脚本的用户

[root@test zwc]# cat ifroot

#!/bin/sh

#ifroot

if [ "$LOGNAME" != "root" ]

#if the user is not root

then

  echo "You need to be root to run this script"

exit 1

else

#yes it is root

  echo "Yes indeed you are $LOGNAME processed"

fi

#normal processing statements go here

[root@test zwc]# chmod 750 ifroot

[root@test zwc]# ./ifroot

Yes indeed you are root processed

[root@test zwc]# cat ifroot

#!/bin/sh

#ifroot

if [ "$LOGNAME" != "root" ]

#if the user is not root

then

  echo "You need to be root to run this script"

exit 1

else

#yes it is root

  echo "Yes indeed you are $LOGNAME processed"

fi

#normal processing statements go here

./ifeditor

 

[root@test zwc]# ./ifroot

Yes indeed you are root processed

Your EDITOR envitonment is not set

[root@test zwc]# cat ifroot

#!/bin/sh

#ifroot

if [ "$LOGNAME" != "root" ]

#if the user is not root

then

  echo "You need to be root to run this script"

exit 1

else

#yes it is root

./ifeditor

fi

[root@test zwc]# ./ifroot

Your EDITOR envitonment is not set

13.将脚本参数传递给系统命令

[root@test zwc]# cat ifdirec

#!/bin/sh

#ifdirec

#assigning $1 to DIRECTORY variable

DIRECTORY=$1

if [ "`ls -A $DIRECTORY`" = "" ] ; then

#if it'a an empty string, then it's empty

echo "$DIRECTORY is indeed empty"

else

#otherwise it is not

echo "$DIRECTORY is not empty"

fi

[root@test zwc]# chmod 750 ifdirec

[root@test zwc]# ./ifdirec

 is not empty

[root@test zwc]# cat ifdirec2

#!/bin/sh

#ifdirec2

DIRECTORY=$1

if [ -z "`ls -a $DIRECTORY`" ]

then

  echo "$DIRECTORY is indeed empty"

else

  echo "$DIRECTORY is no empty"

fi

[root@test zwc]# chmod 750 ifdirec2

[root@test zwc]# ./ifdirec2

 is no empty

14.null:命令用法

[root@test zwc]# vi ifdirectory

[root@test zwc]# cat ifdirectory

#!/bin/sh

#ifdirectory

DIRECTORY=$1

if [ "`ls -A $DIRECTORY`" = "" ]

then

 echo "$DIRECTORY is indeed empty"

 else : # do nothing

fi

[root@test zwc]# chmod 750 ifdirectory

[root@test zwc]# ./ifdirectory

15.测试目录创建结果

 

18.4case语句

18.4.1 简单的case语句

[root@test zwc]# vi caseselect

[root@test zwc]# cat caseselect

#!/bin/sh

#caseselect

echo -n "enter a number from 1 to 5 :"

read ANS

  case $ANS in

1) echo "you select 1"

  ;;

2) echo "you select 2"

  ;;

3) echo "you select 3"

  ;;

4) echo "you select 4"

  ;;

5) echo "you select 5"

  ;;

*)echo "`basename $0`: This is not between 1 and 5"

  exit 1

  ;;

esac

[root@test zwc]# chmod 750 caseselect

[root@test zwc]# ./caseselect

enter a number from 1 to 5 :2

you select 2

[root@test zwc]# ./caseselect

enter a number from 1 to 5 :abc

caseselect: This is not between 1 and 5

18.4.2 对匹配模式使用|

[root@test zwc]# vi caseterm

[root@test zwc]# cat caseterm

#!/bin/sh

#caseterm

echo "choices are.. vt100, vt102,vt220"

echo -n "enter your terminal type :"

read TERMINAL

  case $TERMINAL in

  vt100|vt102) TERM=vt100

  ;;

    vt220) TERM=vt220

  ;;

  *)echo "`basename $0` : Unknown respone"

   echo "setting it to vt100 anyway, so there"

   TERM=vt100

   ;;

esac

export TERM

echo "Your terminal is set to $TERM"

[root@test zwc]# chmod 750 caseterm

[root@test zwc]# ./caseterm

choices are.. vt100, vt102,vt220

enter your terminal type :vt102

Your terminal is set to vt100

[root@test zwc]# ./caseterm

choices are.. vt100, vt102,vt220

enter your terminal type :vt220

Your terminal is set to vt220

[root@test zwc]# ./caseterm

choices are.. vt100, vt102,vt220

enter your terminal type :vt800

caseterm : Unknown respone

setting it to vt100 anyway, so there

Your terminal is set to vt100

18.4.3 提示键入y或n

[root@test zwc]# vi caseans

[root@test zwc]# cat caseans

#!/bin/sh

#caseans

echo -n "Do you wish to proceed [y..n] :"

read ANS

  case $ANS in

  y|Y|yes|Yes) echo "yes is selected"

  ;;

  n|N) echo "no is selected"

  exit 0   #no error so only use exit 0 to terminal

  ;;

  *) echo "`basename $0` :Unknown response"

  exit 1

  ;;

esac

#if we are here then a y|Y|yes|Yes was selected only.

[root@test zwc]# chmod 750 caseans

[root@test zwc]# ./caseans

Do you wish to proceed [y..n] :Y

yes is selected

[root@test zwc]# ./caseans

Do you wish to proceed [y..n] :n

no is selected

[root@test zwc]# vi caseans

[root@test zwc]# ./caseans

Do you wish to proceed [y..n] :dfg

caseans :Unknown response

18.4.4 case与命令参数传递

 

18.5 for循环

18.5.1简单的for循环

[root@test zwc]# cat for_i

#!/bin/sh

#for_i

for loop in 1 2 3 4 5

do

  echo $loop

done

[root@test zwc]# chmod 750 for_i

[root@test zwc]# ./for_i

1

2

3

4

5

 

18.5.4 对for循环使用参数

[root@test zwc]# cat forparam2

#!/bin/sh

#forparam2

for params

do

  echo "You supplied $params as a command line option"

done

[root@test zwc]#chmod 750 forparams2

[root@test zwc]# ./forparam2 myfile myfile2 myfile3

You supplied myfile as a command line option

You supplied myfile2 as a command line option

You supplied myfile3 as a command line option

[root@test zwc]# cat forparam2

#!/bin/sh

#forparam2

for params in "$@"

do

  echo "You supplied $params as a command line option"

done

[root@test zwc]# ./forparam2 myfile myfile2 myfile3

You supplied myfile as a command line option

You supplied myfile2 as a command line option

You supplied myfile3 as a command line option

[root@test zwc]# vi forfind

[root@test zwc]# cat forfind

#!/bin/sh

#forfind

for loop

do

  find / -name $loop -print

done

[root@test zwc]# chmod 750 forfind

[root@test zwc]# ./forfind passwd

/etc/pam.d/passwd

/etc/passwd

/usr/bin/passwd

/usr/share/doc/nss_ldap-226/pam.d/passwd

18.5.5 使用for循环连接服务器

[root@test zwc]# vi forping

[root@test zwc]# cat forping

#!/bin/sh

#forping

HOSTS="itserv dnssevr acctsmain ladpd ladware"

for loop in $HOSTS

do

  ping -c 2 $loop

done

[root@test zwc]# chmod 750 forp

forparam2  forping

[root@test zwc]# chmod 750 forping

[root@test zwc]# ./forping

ping: unknown host itserv

ping: unknown host dnssevr

ping: unknown host acctsmain

ping: unknown host ladpd

ping: unknown host ladware

[root@test zwc]# ping

ping: unknown host

[root@test zwc]# route

Kernel IP routing table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

10.10.11.0      *               255.255.255.0   U     0      0        0 eth0

169.254.0.0     *               255.255.0.0     U     0      0        0 eth0

[root@test zwc]# service network restart

正在关闭接口 eth0：                                        [  确定  ]

关闭环回接口：                                             [  确定  ]

设置网络参数：                                             [  确定  ]

弹出环回接口：                                             [  确定  ]

弹出界面 eth0：                                            [  确定  ]

[root@test zwc]# route

Kernel IP routing table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

10.10.11.0      *               255.255.255.0   U     0      0        0 eth0

169.254.0.0     *               255.255.0.0     U     0      0        0 eth0

default         10.10.11.138    0.0.0.0         UG    0      0        0 eth0

[root@test zwc]# ping

PING (222.73.78.201) 56(84) bytes of data.

64 bytes from 222.73.78.201: icmp_seq=0 ttl=54 time=31.8 ms

64 bytes from 222.73.78.201: icmp_seq=1 ttl=54 time=27.4 ms

64 bytes from 222.73.78.201: icmp_seq=2 ttl=54 time=38.9 ms

 

--- ping statistics ---

3 packets transmitted, 3 received, 0% packet loss, time 2004ms

rtt min/avg/max/mdev = 27.451/32.769/38.968/4.747 ms, pipe 2

[root@test zwc]# vi forping

[root@test zwc]# cat forping

#!/bin/sh

#forping

HOSTS="itserv dnssevr acctsmain ladpd ladware"

for loop in $HOSTS

do

  ping -c 2 $loop

done

[root@test zwc]# ./forping

PING (222.73.78.201) 56(84) bytes of data.

64 bytes from 222.73.78.201: icmp_seq=0 ttl=54 time=29.4 ms

64 bytes from 222.73.78.201: icmp_seq=1 ttl=54 time=28.6 ms

 

--- ping statistics ---

2 packets transmitted, 2 received, 0% packet loss, time 1001ms

rtt min/avg/max/mdev = 28.698/29.088/29.478/0.390 ms, pipe 2

PING (220.181.28.54) 56(84) bytes of data.

64 bytes from 220.181.28.54: icmp_seq=0 ttl=53 time=40.0 ms

64 bytes from 220.181.28.54: icmp_seq=1 ttl=53 time=36.2 ms

 

--- ping statistics ---

2 packets transmitted, 2 received, 0% packet loss, time 1001ms

rtt min/avg/max/mdev = 36.218/38.148/40.079/1.940 ms, pipe 2

PING jupiter.sina.com.cn (61.172.201.194) 56(84) bytes of data.

64 bytes from 61.172.201.194: icmp_seq=0 ttl=247 time=4.93 ms

64 bytes from 61.172.201.194: icmp_seq=1 ttl=247 time=5.00 ms

 

--- jupiter.sina.com.cn ping statistics ---

2 packets transmitted, 2 received, 0% packet loss, time 1002ms

rtt min/avg/max/mdev = 4.931/4.966/5.001/0.035 ms, pipe 2

18.5.6 使用for循环备份文件

18.5.7 多文件转换

18.5.8 多sed删除操作

18.5.9 循环计数

18.5.10 for循环和本地文档

18.5.11 for循环嵌入

 

18.6 until循环

18.6.1简单的until循环

[root@test zwc]# vi until_who

[root@test zwc]# cat until_who

#!/bin/sh

#until_who

IS_ROOT=`who | grep root`

until [ "$IS_ROOT" ]

do

   sleep 5

done

echo "Watch it. root in" | mail zwc

[root@test zwc]# chmod 750 until_who

[root@test zwc]# ./until_who

[root@test /]# ls

abc.txt  dev   initrd      media  opt   sbin     swap  usr

bin      etc   lib         misc   proc  selinux  sys   var

boot     home  lost+found  mnt    root  srv      tmp   zwc

[root@test /]# cd var

[root@test var]# ls

account  crash  empty  gdm  local  log   nis  preserve  spool  tux  yp

cache    db     ftp    lib  lock   mail  opt  run       tmp    www

[root@test var]# cd spool/

[root@test spool]# ls

anacron  clientmqueue  cups  mail    repackage  squid    vbox

at       cron          lpd   mqueue  samba      up2date

[root@test spool]# cd mail

[root@test mail]# ls

oracle  root  zwc

[root@test mail]# cat zwc

From root@test  Wed Sep 24 20:52:34 2008

Return-Path:

Received: from test (localhost.localdomain [127.0.0.1])

        by test (8.13.1/8.13.1) with ESMTP id m8OCqYgw003050

        for ; Wed, 24 Sep 2008 20:52:34 +0800

Received: (from root@localhost)

        by test (8.13.1/8.13.1/Submit) id m8OCqYVg003020

        for zwc; Wed, 24 Sep 2008 20:52:34 +0800

Date: Wed, 24 Sep 2008 20:52:34 +0800

From: root

Message-Id: <200809241252.m8OCqYVg003020@test>

To: zwc@test

 

Watch it. root in

18.6.3 监视磁盘空间

[root@test zwc]# cat until_mon

#!/bin/sh

#until_mon

#get percent column and srtip off header row from df

LOOK_OUT=`df | grep /boot | awk '{print $5}' | sed 's/%//g'`

echo $LOOK_OUT

until [ "$LOOK_OUT" -gt "5" ]

do

  echo "Filesystem..logs is nearly full" | mail zwc

  exit 0

done

[root@test zwc]# chmod 750 until_mon

[root@test zwc]# ./until_mon

10

[root@test zwc]#cd /var/spool/mail

[root@test mail]#cat zwc

From root@test  Wed Sep 24 23:39:12 2008

Return-Path:

Received: from test (localhost.localdomain [127.0.0.1])

        by test (8.13.1/8.13.1) with ESMTP id m8OFdC0X029900

        for ; Wed, 24 Sep 2008 23:39:12 +0800

Received: (from root@localhost)

        by test (8.13.1/8.13.1/Submit) id m8OFdCiF029880

        for zwc; Wed, 24 Sep 2008 23:39:12 +0800

Date: Wed, 24 Sep 2008 23:39:12 +0800

From: root

Message-Id: <200809241539.m8OFdCiF029880@test>

To: zwc@test

 

Filesystem..logs is nearly full

18.7 while循环

18.7.1 简单的while循环

[root@test zwc]# cat whilecount

#!/bin/sh

#whilecount

COUNTER=0

while [ $COUNTER -lt 5 ]

do

  #add one to the counter

  COUNTER=`expr $COUNTER + 1`

  echo $COUNTER

done

[root@test zwc]# chmod 750 whilecount

[root@test zwc]# ./whilecount

1

2

3

4

5

18.7.2 使用while循环读键盘输入

18.7.3 使用while循环从文件中读取数据

[root@test zwc]# cat name.txt

a:b:c

d:e:f

h:i:j

[root@test zwc]# cat while

[root@test zwc]# cat whileread

#!/bin/sh

#whileread

while read LINE

do

  echo $LINE

done < name.txt

[root@test zwc]# chmod 750 whileread

[root@test zwc]#

[root@test zwc]# ./whileread

a:b:c

d:e:f

h:i:j

18.7.4 使用IFS读文件

[root@test zwc]# vi whilereadifs

[root@test zwc]# cat whilereadifs

#!/bin/sh

#whilereadifs

#save the setting of IFS

SAVEDIFS=$IFS

#assign new seprarator to IFS

IFS=:

while read NAME DEPT ID

do

  echo -e "$NAME\t $DEPT\t $ID"

done < name.txt

# restore the setting of IFS

IFS=$SAVEDIFS

 

[root@test zwc]# chmod 750 whilereadifs

[root@test zwc]# ./whilereadifs

a        b       c

d        e       f

h        i       j

18.7.5 带有条件测试的文本处理

root@test zwc]# cat whileread_file

#/bin/sh

#whileread_file

#initialise variables

SAVEDIFS=$IFS

IFS=:

HOLD_FILE=hold_file

NAME_MATCH="James Lenod"

INPUT_FILE=names.txt

 

#creat a new HOLD_FILE each time, in case script is continuously run >$HOLD_FILE

while read NAME DEPT ID

do

   #echo all information into holdfile with redrection

   echo $NAME $DEPT $ID >>$HOLD_FILE

   #is it a match ???

  if [ "$NAME" = "$NAME_MATCH" ]; then

     #yes then nice exit

     echo "all entries up to and including $NAME_MATCH are in $HOLD_FILE"

     exit 0

   fi

done < $INPUT_FILE

#restore IFS

IFS=$SAVEDIFS

[root@test zwc]# chmod 750 whileread_file

[root@test zwc]# ./whileread_file

[root@test zwc]# ./whileread_file

all entries up to and including James Lenod are in hold_file

 

 

18.8 使用break和continue控制循环

188.1 break

18.8.2 跳出case语句

[root@test zwc]# cat breakout

#!/bin/sh

# breakout

# while : means loop forever

while :

do

  echo -n "Enter any namber [1..5] :"

  read ANS

  case $ANS in

    1|2|3|4|5) echo "great you entered a number between 1 and 5"

    ;;

    *)echo "Wrong number..bye"

    ;;

   esac

done

[root@test zwc]# chmod 750 breakout

[root@test zwc]# ./breakout

Enter any namber [1..5] :1

great you entered a number between 1 and 5

Enter any namber [1..5] :5

great you entered a number between 1 and 5

Enter any namber [1..5] :9

Wrong number..bye

Enter any namber [1..5] :1

great you entered a number between 1 and 5

Enter any namber [1..5] :2

(陷入死循环)

 

[root@test zwc]# vi breakout

[root@test zwc]# cat breakout

#!/bin/sh

# breakout

# while : means loop forever

while :

do

  echo -n "Enter any namber [1..5] :"

  read ANS

  case $ANS in

    1|2|3|4|5) echo "great you entered a number between 1 and 5"

    ;;

    *)echo "Wrong number..bye"

    break

    ;;

   esac

done

[root@test zwc]# ./breakout

Enter any namber [1..5] :3

great you entered a number between 1 and 5

Enter any namber [1..5] :8

Wrong number..bye

[root@test zwc]#

(跳出循环,回到shell提示符下)

18.8.3 continue

continue命令不会跳出循环，只是跳过这个循环

18.8.4 浏览文件行

[root@test zwc]# cat name2.txt

------LISTING OF PERSONNAL FILE----

--- TAKEN AS AT 06/1999 ----

Louise Conrad:Accounts:ACC8987

Peter James:Payroll:RP489

Fred Terms:Customer:CUS012

James Lenod:Accounts:ACC887

Frank Pavely:Payroll:RP487

[root@test zwc]# cat whilecontinue

#!/bin/sh

#whilecontinue

SAVEDIFS=$IFS

IFS=:

INPUT_FILE=name2.txt

NAME_HOLD="Peter James"

LINE_NO=0

 

if [ -s $INPUT_FILE ]; then

  while read NAME DEPT ID

  do

    LINE_NO=`expr $LINE_NO + 1`

    if [ "$LINE_NO" -le "2" ]; then

       #skip if the count is less than 2

      continue

    fi

    if [ "$NAME" = "$NAME_HOLD" ]; then

    #skip if the name in NAME_HOLD is Peter James

    continue

    else

      echo "$NAME $DEPT $ID"

       #all the processing goes here

     fi

  done < $INPUT_FILE

 IFS=$SAVEDIFS

else

  echo "`basename $0` : Sorry file not found or there is no date in the file"

  exit1

fi

[root@test zwc]#chmod 750 whilecontinue

[root@test zwc]# ./whilecontinue

Louise Conrad Accounts ACC8987

Fred Terms Customer CUS012

James Lenod Accounts ACC887

Frank Pavely Payroll RP487

18.9菜单

[root@test zwc]# cat menu

#!/bin/sh

# menu

# set the date, user and hostname up

MYDATE=`date +%d/%m/%y`

THIS_HOST=`hostname -s`

USER=`whoami`

#loop forever!

while :

do

  # clear the screen

  tput clear

  # here documents starts here

cat <

 

--------------------------------------------------------------------

User: $USER              Host:$THIS_HOST            Date:$MYDATE

--------------------------------------------------------------------

                   1 : List files in current directory

                   2 : Use the vi editor

                   3 : See who is on the system

                   H : Help screen

                   Q : Exit Menu

----------------------------------------------------------------------

MAYDAY

 

# here document finished

echo -e -n "\tYour Choice [1,2,3,H,Q] >"

read CHOICE

  case $CHOICE in

  1)ls

  ;;

  2)vi

  ;;

  3)who

  ;;

  H|h)

# use a here document for the help screen

cat <

This is the help screen,nothing here yet to help you!

MAYDAY

  ;;

  Q|q)exit 0

  ;;

  *)echo -e "\t\007unknown user response "

  ;;

  esac

echo -e -n "\tHit the return key to continue"

read DUMMY

done

[root@test zwc]#chmod 750 menu

[root@test zwc]#./menu

 

 

--------------------------------------------------------------------

User: root              Host:test            Date:25/09/08

--------------------------------------------------------------------

                   1 : List files in current directory

                   2 : Use the vi editor

                   3 : See who is on the system

                   H : Help screen

                   Q : Exit Menu

----------------------------------------------------------------------

        Your Choice [1,2,3,H,Q] >3

root     :0           Sep 24 20:15

root     pts/1        Sep 25 00:32 (:0.0)

root     pts/2        Sep 25 03:20 (:0.0)

        Hit the return key to continue