Simple shell Script Programming example (looping)

For loop

For variable name in list;

Loop body

Done

Implementation mechanism:

Assigns the element in the list to the "variable name" in turn; The loop body is executed once each assignment; Until the elements in the list are exhausted, the loop ends

List Generation Method:

(1) Give the list directly

(2) List of integers:

(a) {start: End

(b) $ (seq[start [step]] end)

(3) command to return a list

$ (COMMAND)

(4) using glob, such as: *.sh

(5) variable reference;

[email protected], $*

1. Determine the type of all files in the/var/directory

①

#!/bin/bashfor filename in /var/* ;d o    if [ -l  "$ FileName " ] ;then        echo " $filename  is  Link file "    elif [ -f " $filename " ];then         echo  "$filename  is common file"     elif  [ -b  "$filename"  ];then        echo  "$ Filename is block file "    elif [ -c " $filename " ];then         echo  "$filename  is char file"      elif [ -S  "$filename"  ] ;then         echo  "$filename  is socket file "     elif [ -d   "$filename"  ] ;then        echo  "$filename  is directory"      else        echo  "Unknow"      Fidone

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Ii

#!/bin/bashfor f1 in /var/* ; do    ff= ' ls -ld  $f 1  | cut -c1 '     case  $ff  in    l)          echo  "$f 1 is link file"     ;;     B)         echo  "$f 1 is blcok  file  "    ;;     c)         echo  "$f 1 is char  file "    ;;     s)         echo  "$f 1 is socket  file "    ;;     -)         echo  "$f 1 is file"     ;;     d)         echo  "$f 1  is diR "    ;;     *)         echo  "$f 1  is  other  "    esacdone

2, add 10 user user1-user10, password with user name

#!/bin/bash# Add 10 user user1-user10, password with user name for I in {1..10};d o ID user$i &>/dev/null if [$?-eq 0];then Echo "User$i is exist" else Useradd user$i echo "User$i" | passwd--stdin user$i &>/dev/null echo "Add user$i finished" fi done

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Ii

Delete the above user

#!/bin/bashfor i in {1..10};        Doid user$i &>/dev/null if [$?-eq 0];then userdel-r user$i echo "user$i is delete" Else echo "user$i isn't exist" fi done

3. The/ETC/RC.D/RC3.D directory has several files starting with K and beginning with S, respectively reading each file, the output of the file starting with K is the file plus stop, and the file output with s begins with the filename plus start;

The #!/bin/bash#/etc/rc.d/rc3.d directory has a number of files starting with K and beginning with S, respectively reading each file, the output of a file starting with K is a file plus stop, the file output with s begins with the filename plus start;for filename in/ etc/rc.d/rc3.d/*;d o ff= ' basename "$filename" |      Cut-c1 ' Case $ff in [Kk]) echo "$filename stop";;        [Ss])      echo "$filename start";; *) echo "other" Esacdone

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4, write a script, prompt to enter the value of positive integer n, calculate the sum of 1+2+3+...N

#!/bin/bashread-p "Please a number:" N1if [[$n 1 =~ ^-?[ [:d Igit:]]            +$]];then If [$n 1-gt 0];then sum=0 for i on ' seq $n 1 ';d o sum=$[$sum + $i] Done echo "Sum is $sum" Else echo "$n 1 was not positive integer" fi else echo "need a number" fi

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5, write a script, prompt please enter the network address, such as 192.168.0.0, determine the input network segment host online status

#!/bin/bashread-p "Please input a IP:" Ipi= ' echo $ip |cut-d.-f1-3 '. if [[$ip =~ ^ ([1-9]|[ 1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) \. ([0-9]| [1-9] [0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) \.) {2} ([0-9]| [1-9] [0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) $]]; then for j in {1..255};d o ping-c1-w1 $i $j &>/dev/null && Amp echo "$i $j is on" | | echo "$i $j is Off" doneelse echo "This is not IP" fi~

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6. Print 99 multiplication table

#!/bin/bashi=1for i in {1..9};d o to J in ' seq $i ';d o echo-ne "$j * $i =$[$i * $j]\t" Done Echodone

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While loop

While CONDITION; Do

Loop body

Done

CONDITION: cyclic control conditions; Before entering the cycle, make a judgment; once each loop is judged again; the condition is "true", then a loop is executed until the condition test state is "false" to terminate the loop

Therefore: Condtion generally should have a cyclic control variable, and the value of this variable will be continuously corrected in the loop body

Entry condition: condition is true;

Exit Condition: Condition is false

1. The sum of all positive integers within 100

#!/bin/bashi=1sum=0while [$i-le];d o sum=$[$sum + $i] Let i++ do echo "Sum is $sum"

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2, through the ping command to detect the 172.16.250.1-254 range of all the host's online status, statistics online host and the number of offline host.

#!/bin/bashread-p "Please input IP" ipi= ' echo $ip | cut-d.-f1-3 '. j=0if echo $ip | Egrep "^ ([1-9]|[ 1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) \. ([0-9]| [1-9] [0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) \.) {2} ([0-9]| [1-9] [0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) $ "; then while [$j-le 255];d o ping-c1-w1 $i $j &>/dev/null &     amp;& echo "$i $j is on" | | echo "$i $j is Off" let J + + do else echo "This isn ' t IP" fi

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3. Print 99 multiplication table

#!/bin/bashi=1while [$i-lt];d o j=1 while [$j-le $i];d o echo-ne "$i * $j =$[$i * $j]\t" let J + + Do echo let i++ do

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4. Generate 10 random numbers using variable random, output this 10 number, and show the largest and smallest of them

#!/bin/bashi=1a= $RANDOMmax = $amin = $awhile [$i-le];d o [$max-le $a] && max= $a [$min-ge $a] &&am P Min= $a echo "$a" a= $RANDOM let i++ doneecho "max number was $max" echo "min number is $min" ~

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5. Print Chess board

#!/bin/bashi=1while [  $i  -le 8 ];d o      j=1     while [  $j  -le 8 ];d o         sum=$[$i + $j]      n=$[$sum%2]         if [  $n  -eq 0 ];then             echo -ne  "\033[41;1m  \033[0m"          else             echo -ne  "\033[43;1m  \033[0m"         fi        let j++     done     let i++     echodone 

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Until cycle

Until CONDITION; Do

Loop body

Done

Entry condition: CONDITION is False

Exit Condition: CONDITION is True

1, every 3 seconds to the system to obtain the information of the user who has logged on, if the user hacker logon, the logon time and the host record in the log/var/log/login.log, and prompts the user to exit the system.

#!/bin/bashuntil who | Grep-q "^hacker\>"; Dosleep 3donewho| grep "^hacker\>" | Tr-s "" | Cut-d ""-f3-5 >>/var/log/login.logecho "You should logout" | Mail Hackerecho "Hacker is login"

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2, randomly generated within 10 of the number, to achieve the word guessing game, the hint is relatively large or small, equal to exit.

#!/bin/bashread -p  "guess number! please enter a numer{0-10}: "   nif [[  $n  =~ ^[[:d igit:]]+$ ]] ;then    i=$[$RANDOM%11]     until [  $n  -eq  $i  ] ; do         if [  $n  -gt  $i  ] ; then             echo  "It ' s too large "          else              echo  "It ' s too small "         fi           read -p  "Try again:"  n     done    echo  "You are right!!!" else    echo  "please input a number !!! " Fi

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1, write a script: print isosceles triangle

#!/bin/bashread -p  "please input a line number "  nif [[  "$n"  =~ ^[[:d igit:]]+$ ]] ;then     for i in  ' seq   $n '  ;d o           for j in  ' seq $[$n-$i] ';d o            echo -n   " "         done         for k in  ' seq $[$i *2-1] ';d o             echo -n  "*"         done         echo        let i++      doneelse    echo  "need a number!"     exit 2fi

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2, using until cycle to achieve the chess board

#!/bin/bashi=1red= "\033[41;1m  \033[0m" yellow= "\033[43;1m   \033[0m "until [  $i  -gt 8 ] ;d o    j=1      until [  $j  -gt 8 ] ;d o         sum=$[$i + $j]        z=$[$sum%2]         if [  $z  -eq 0 ] ;then             echo -ne  "$red"          else             echo -ne   "$yellow"         fi           let j++     done    let i++      echodone 

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This article is from the "I ' m Groot" blog, so be sure to keep this source http://groot.blog.51cto.com/11448219/1840068

Simple shell Script Programming example (looping)