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Command line arguments, the source command

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• Program scripts
  • You can write Tcl commands and store it in a file for execution

  • To run a Tcl program, use:

    ns FILENAME ARG1 ARG2 ...

  • You can provide arguments to the script.

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• Getting to the command line arguments
  • Tcl uses the (global) variables to store information on the command line:

    argc: The number of command line arguments argv0: The name of the script file argv: The rest of the command line arguments (it's a list)

  • Example: Standard way to loop through a list

    puts "There are $argc arguments to this script" puts "The name of this script is $argv0" if {$argc > 0} {puts "The other arguments are: $argv" } set k 1 foreach i $argv { puts "arg $k is $i" incr k }

    (The foreach loop was discussed in this webpage: click here )

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  • Example Program: (Demo above code)                        
    • Prog file: click here

    How to run program:

    1. Right click and save program
    2. Run with: ns arg.tcl abc def

• An easier way to get to the command line arguments
  • The argument list variable argv is indexed using numbers, starting with 0

  • Because it uses numeric indices, we can access the command line arguments using a for loop

  • Example:

    puts "There are $argc arguments to this script" puts "The name of this script is $argv0" if {$argc > 0} {puts "The other arguments are: $argv" } for {set i 0} {$i < [llength $argv]} {incr i} { puts "arg $i is [lindex $argv $i]" }

    (The for loop was discussed in this webpage: click here )

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  • Example Program: (Demo above code)                        
    • Prog file: click here

    How to run program:

    1. Right click and save program
    2. Run with: ns arg.tcl abc def

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• Source: Making your own library of commands
  • Now that you have seen how to use the proc command to creates new Tcl commands, you want to learn a Tcl command to reading a file that contain those commands (you need to make Tcl learn these commands every time you use Tcl)

  • The source command will load a file and execute it.

    Thus, if the file contains procedure definitions, Tcl will learn the new commands.

  • The source also allows you to break a program up into multiple files:

    source FILENAME

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• Further reading
  • Command line argument: click here
  • Source command click here