Реферат: Scripts Essay Research Paper 30
Название: Scripts Essay Research Paper 30 Раздел: Топики по английскому языку Тип: реферат |
Scripts Essay, Research Paper 3.0 Variables Scripts may contain variables. Variable names must begin with a letter or an underscore (’_'), and may contain any sequence of upper- or lower-case letters, digits, and underscores. You cannot use a reserved word as a variable name. For more information, see the list of reserved words at the end of this document. You must declare variables before you use them. When you declare a variable, you must also define its type. A variable of a certain type may only contain values of that same type. The following three types of variables are supported: Type Description integer A negative or positive number, such as 7, -12, or 5698. string A series of characters enclosed in double-quotes; for example, “Hello world!” or “Enter password:”. boolean A logical boolean value of TRUE or FALSE. Variables are assigned values using the following assignment statement: variable = expression The variable gets the evaluated expression. Examples: integer count = 5 integer timeout = (4 * 3) integer i boolean bDone = FALSE string szIP = (getip 2) set ipaddr szIP 3.1 System Variables System variables are set by scripting commands or are determined by the information your enter when you set up a Dial-Up Networking connection. System variables are read-only, which means they cannot be changed within the script. The system variables are: Name Type Description $USERID String The user identification for the current connection. This variable is the value of the user name specified in the Dial-Up Networking Connect To dialog box. $PASSWORD String The password for the current connection. This variable is the value of the user name specified in the Dial-Up Networking Connect To dialog box. $SUCCESS Boolean This variable is set by certain commands to indicate whether or not the command succeeded. A script can make decisions based upon the value of this variable. $FAILURE Boolean This variable is set by certain commands to indicate whether or not the command failed. A script can make decisions based upon the value of this variable. These variables may be used wherever an expression of a similar type is used. For example, transmit $USERID is a valid command because $USERID is a variable of type string. 4.0 String Literals Scripting for Dial-Up Networking supports escape sequences and caret translations, as described below. String Literal Description ^char Caret translation If char is a value between ‘@’ and ‘_’, the character sequence is translated into a single-byte value between 0 and 31. For example, ^M is converted to a carriage return. If char is a value between a and z, the character sequence is translated into a single-byte value between 1 and 26. If char is any other value, the character sequence is not specially treated. Carriage return Linefeed \” Double-quote \^ Single caret \< Single ' = Relational Integers == != Equality Integers, strings, booleans and Logical AND Booleans or Logical OR Booleans Examples: count = 3 + 5 * 40 transmit “Hello” + ” there” delay 24 / (7 – 1) |