003 scripting

003 scripting

• 1.
  SHATRIX Scripting A  Creating and Running Scripts  Basic Script Architecture G  echo E  Variables N read   Conditional statements D  Loops A  Examples
• 2.
  Creating and RunningScripts  Scripts are normal text files with x permission  touch  script­name  chmod  777  script­name  chmod  u+x  script­name  To run a script:  full path  ./script­name  sh  script­name  bash  script­name
• 3.
  Basic Script Architecure  #!(shell-path) #!/bin/bash  variables definition  echo ”Welcome”  read var1  read variables from user  echo $var1  loops  conditional statements  print output to terminal  pipe & redirection to other files
• 4.
  echo  echo displays a line of text  echo  ”string”  echo  $variable­name  echo  ”string  $var­name”  echo  ”string  $var­name  another­string”  echo $(command) echo ”Welcome Linux users”
• 5.
  Variables  Define a variable  variable­name=VALUE  Print a variable to screen  echo  $variable­name  System variables:  Normal: has to be changed with each user  HOME     PWD    SHELL  Environmental: changes with the login shell only  login shell with (su ­)  PATH  env
• 6.
  read  read take a value from the user to a variable  read  variable­name  read  ­p  ”string”  variable­name read  ­p  ”Enter your name”  name echo  ”Your name is $name”
• 7.
  Conditional Statements  if statement #!/bin/bash if [ condition ] x=5 if [ $x = 5 ]  then then    things to do echo ”right”  elif [ another­cond. ] else echo ”wrong”  then fi    things to do  else    things to do fi
• 8.
  Conditional Statements  case statement #!/bin/bash case $variable­name in x=5    value_1) case $x in       things to do;; 4) echo ”x=4”;;    value_2) 5)       things to do;; echo ”x=5” echo ”ok”;;    *) *)       default action;; echo ”I don't know”;; esac esac
• 9.
  Loops  for loop for  VARIABLE  in  ARRAY do     things on each value done #!/bin/bash for i in 1 2 3 4 5 do echo ”current value is $i” done
• 10.
  Loops  while loop while  [ condition ] do #!/bin/bash     things to do VAR=0 done while [ $VAR ­lt 3 ]; do    echo $VAR    VAR=$[$VAR+1]  equal (=) done  not equal (!=)  Less than (­lt)  Greater than (­gt)
• 11.
  Examples (User Login) #!/bin/bash user_name="shatrix" password="13" read ­p "User Name: " login_name stty ­echo read ­p "Password: " login_pass stty echo echo "" if [ $login_name = $user_name ];  then if [ $login_pass = $password ];  then echo "Now you are logged in....." else echo "Error, wrong password, try again" fi else echo "Error, user name doesn't exist" fi
• 12.
  Examples (Calculator) #!/bin/bash read ­p "Enter First Number: " f_num read ­p "Enter Second Number: " s_num read ­p "Enter Operation: " op case $op in +)     echo "$f_num + $s_num = $[$f_num+$s_num]";; ­)     echo "$f_num ­ $s_num = $[$f_num­$s_num]";; x)     echo "$f_num x $s_num = $[$f_num*$s_num]";; /)     echo "$f_num / $s_num = $[$f_num/$s_num]";; esac
• 13.
  Examples (Modified Calculator) #!/bin/bash read ­p "Enter First Number: " f_num read ­p "Enter Second Number: " s_num read ­p "Enter Operation: " op case $op in +)     echo "$f_num + $s_num = $[$f_num+$s_num]";; ­)     echo "$f_num ­ $s_num = $[$f_num­$s_num]";; x)     echo "$f_num x $s_num = $[$f_num*$s_num]";; /)     if [ $s_num != 0 ];  then       echo "$f_num / $s_num = $[$f_num/$s_num]"     else       echo "Error, division by zero"     fi;; *)     echo "Wrong operation, please try again !!!" esac
• 14.
  Examples (PhoneBook)