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Scripts


Index


Introduction

Scripts are programs which are built of commands. Those commands can be Shell commands which you can find in the C: directory or any other AROS application which can be started from Shell. Example:

CD ram:
DIR
sys:tools/editor

You can create the scripts with any text editor, e.g. sys:tools/Editor.

The default storage location for scripts is S:, but you can use any directory. The search path of the Shell is used to find the script.

Execution

Scripts can be executed from Shell with the Execute command, e.g.:

execute myscript

Alternatively, you can set the s bit. This allows to execute the script by just entering the name, e.g.:

protect myscript s add
myscript

You can start scripts from Wanderer if you add an icon to it and set the default tool to c:iconx.

Special script characters

;

Comments; anything following the ; is ignored, e.g.:

ASSIGN foo: sys:c ; Create an assign
$
  1. Expand environment variables, e.g.:

    ECHO "Current language is $LANGUAGE"
    
  2. Within brackets: set default value for parameters. The brackets can be changed with the dot commands .BRA and .KET:

    <param$default>
    

The $ can be changed with the .DOLLAR command. To specify parameters, there must be a .KEY command in the script.

$$
<$$> is replaced by the current process number.

Dot commands

Dot commands are keywords which start with a dot. Their usage will be explained in the chapter about parameter substitution. Dot commands are case insensitive.

.KEY <template>

Argument template. The arguments must be separated by comma, no space is allowed. You can add /A and /K to the arguments.

/A
required argument.
/K
argument name must be written.

Example:

.KEY FILENAME/A,TO/K
.DOT <char>
Changes the dot character to the given argument.
.BRA <char>
Changes the character for the opening bracket. Default is <.
.KET <char>
Changes the character for the closing bracket. Default is >.
.DOLLAR <char>
Changes the character for the dollar sign.
.DEF <parameter> <default value>
Sets default value for a parameter.
.<space><comment>
Comment line, better use ;.
.
Empty comment line.

Parameter substitution

Scripts can be called with parameters. To be able to handle the parameters the script must start with a dot command (preferable .KEY):

.KEY text/A
.BRA {
.KET }
ECHO "{text}"

Opmerking

Because of a bug in the Shell you always have to overwrite the angle brackets <, > with .BRA and .KEY (a good choice would be curly brackets {, }).

Another reason for always overwriting the angle brackets is to avoid confusion with input/output redirection.

Hint

Enclose parameters in double quotes to avoid troubles when the parameter contains white-space, as white-space is used for parameter separation, e.g.: use TYPE "{FILE}" rather than TYPE {FILE}.

Condition flags

Commands are returning a number which indicates condition of execution.

0...4
Success.
5...9
Warn.
10...19
Error.
20...
Failure.

Shell commands return only the values 0, 5, 10 and 20. In the Shell a limit indicates for what returned value a script should stop executing. By default this limit is 10, but it can be changed with the FailAt command.

Some query commands use the flag to tell about the result, e.g.:

ASK "Continue?"
IF WARN              ; A WARN means a Yes.
    COPY a.dat b.dat
ENDIF

Conditional blocks

The If command allows to define blocks which are only executed if the given conditions are met. Some examples:

IF WARN
IF ERROR
IF FAILURE
IF NOT EXISTS "ram:abc"
IF $var EG "FOOBAR"
    ...
ENDIF

Example with Else specifying an alternative block:

IF EXISTS "ram:file.txt"
    TYPE "ram:file.txt"
ELSE
    ECHO "File doesn't exist"
ENDIF

Skipping

With the Skip command, you can jump to labels which you have defined with Lab:

IF EXISTS "ram:file.txt"
    SKIP message
ELSE
    ECHO "File doesn't exist."
    QUIT
ENDIF
LAB message
ECHO "File exists."

Interactivity

Some commands interrupt the script execution until the user has given some input.

The Ask commands prints a message and sets the condition flag to WARN if the input was "y(es)".

RequestChoice, RequestFile and RequestString print their results to the standard output. To be able to process it you have to redirect their output to a file, e.g.:

REQUESTSTRING >ENV:reqstrres "Enter a string"

Storing in ENV: has the advantage that the file can be handled as an environment variable, as explained below.

Environment variables

Variables can be set with Set and SetEnv.

Set creates local variables which exist only in the current Shell and all Shells created from the current Shell.

SetEnv creates global variables that are available in all Shells. The content is stored in files in the ENV: directory with the variable name as filename.

To use the variable's contend you have to prefix it with a $ sign, e.g.:

ECHO "Contend $reqstrres"

This isn't limited to scripts. You can use environment variables directly in the Shell.

Hint

Enclose expanded variables in double quotes to avoid troubles when the variable may contain white-space, as white-space is used for parameter separation, e.g.: better use TYPE "$FILE" than TYPE $FILE.

Some variables are handled by the Shell:

ECHO
Setting it to ON (SET ECHO ON) enables command echoing, i.e. all commands are printed before they are executed. This can be used for debugging.

Quitting

You can use the Quit command if you want to exit the script before it has reached the last line.

Automatic script creation

The LFORMAT option of the List command makes it possible to format the output in such a way that it can be executed as a script:

LIST #? TO T:typeall LFORMAT="TYPE *"%P%N*""
EXECUTE T:typeall

The reason for *" is to ensure that the paths in the generated file are enclosed in double quotes.

Special scripts

During booting, AROS executes the script s:startup-sequence. That file is supposed to be read-only. If you have your own commands that you want to be called during start-up, add them to the file s:user-startup. The script s:shell-startup is executed every time you open a new Shell.


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