Lab 2 Shell Script Operating System Lab NCHU

Lab #2 Shell Script Operating System Lab NCHU System & Network Lab

What is Shell Script? • It is often considered a simple domain-specific programming language. • Typical operations performed by shell scripts include file manipulation, program execution, and printing text. NCHU System & Network Lab

Example #1 #!/bin/bash #use to print out “Hello ! How are you? ” #2007/09 hello=Hello! How are you? echo $hello Output: [root@localhost~ ]#sh eample 1. sh Hello! How are you? NCHU System & Network Lab

Example #2: echo #!/bin/bash #use to differentiate “ and ‘ #2007/09 name=“oslab” name 1=“test is $name” name 2=‘test is $name’ echo $name 1 echo $name 2 Output: [root@localhost~ ]#sh eample 2. sh oslab test is $name NCHU System & Network Lab

Example #3: declare(1/2) • declare –afir – – a for array f for function i for integer r for read only NCHU System & Network Lab

Example #3: declare(2/2) #!/bin/bash #use to learn “declare” #2007/09 number 1=2*3+5*13 -32+25 declare –i number 2=2*3+5*13 -32+25 echo ”answer is $number 1” echo ”answer is $number 2” Output: [root@localhost~ ]#sh eample 3. sh answer is 2*3+5*13 -32+25 answer is 64 NCHU System & Network Lab

Example #4: read #!/bin/bash #use to learn “read” #2007/09 echo “keyin your name and Enter to start” read name echo “This is the data you keyin=>$name” Output: [root@localhost~ ]#sh eample 4. sh keyin your name and Enter to start oslab This is the data you keyin=>oslab NCHU System & Network Lab

Example #5: If…then…elseif…then…endif(1/3) Syntax: If[ … ] &&(||) [ … ]; then …… elif[ … ] &&(||) [ … ]; then …… else …… fi #!/bin/bash #use to learn “if …then…fi” #2007/09 echo “press y to continue” read yy if[ “$yy”=“y” ]; then echo “continue…” else echo”stop…” fi Output: [root@localhost~ ]#sh eample 5. sh press y to continue y continue… NCHU System & Network Lab

Example #5: Exercise(2/3) • When we keyin “y”, the script will continue. – But when we keyin ”Y”, the script will stop. • How to improve the script that let this script print “continue…” when we keyin “Y” or “y”. NCHU System & Network Lab

Example #6: parameter(1/3) #!/bin/bash #use to define parameter #2007/09 echo “This script’s name => $0” echo “parameters $1 $2 $3” Output: [root@localhost~ ]#sh example 6. sh num 1 num 2 num 3 This script’s name => example 6 arameters num 1 num 2 num 3 NCHU System & Network Lab

Example #6: Exercise(2/3) • Use example #5 and example #6 – Keyin “hello” then print “Hello! how are you? ” – If keyin “null”, print “please input parameters” – If keyin any words except “hello”, print “only accept parameter is hello” NCHU System & Network Lab

Example #7: case(1/5) • Direction and interaction • Direction uses parameters that are written in a script. • Interaction lets user keyin the parameters. NCHU System & Network Lab

Example #7: case(2/5) • Syntax: case (type) in type 1) …. . . ; ; type 2) …. . . ; ; type 3) …. . . ; ; . . . *) esca #!/bin/bash #using case mode: direction #2007/09 echo “this script will print your selection” case $1 in one) echo “your choice is one” ; ; two) echo “your choice is two” ; ; three) echo “your choice is three” ; ; *) echo “keyin parameters: one | two | three” esac NCHU System & Network Lab

Example #7: case(3/5) Output: [root@localhost~ ]#sh example 7. sh this script will print your selection keyin parameters: one | two | three [root@localhost~ ]#sh example 7. sh three this script will print your selection your choice is three NCHU System & Network Lab

Example #7: Exercise(4/5) • How to use interaction? • This script will ask you enter a selection form keyboard • Example: press your selection one, two, or three. two your choice is two NCHU System & Network Lab

Example #8: for and loop #!/bin/bash #using for and loop 1+2+3+…+100 #2007/09 declare –i i declare –i s Output: [root@localhost~ ]#sh example 8. sh The count is 5050 for ((i=1; i<=100; i++)) do s=s+i done while [ “$i” != “ 101”] do s=s+i i=i+1 done until [“$i” = “ 101”] do s=s+i i=i+1 done echo “the count is $s” NCHU System & Network Lab

Final Exercise • User management – “adduser” command allows us to create a new user – Please write a shell script to accomplish the user creation task interactively. – Let’s say that the executable file is named myadduser. NCHU System & Network Lab

myadduser • The user adding procedure includes – (i) a user adding prompt (such as “adding a new user…. ” ), – (ii) user’s login, group, password, home directory, and login shell for establishing the necessary attributes for the new user, and – (iii) a message of whether continue to add more users or not (such as “adding more users (y/n)? ”). • Note that the password has to be typed twice and be verified for its coincidence. • Running myadduser should produce the following interactive outcome: NCHU System & Network Lab

Reference • Wikipedia – http: //en. wikipedia. org/wiki/Shell_script • 鳥哥的 Linux 私房菜 – http: //linux. vbird. org/ • Neil Matthew, Richard Stones, “Beginning Linux Programming, 2 nd Edition ”, Wrox, 2002 NCHU System & Network Lab