This global variable is provided by tclsh and wish mainline code (and '''NOT''' the tcl or tk libraries). It gives you the arguments the app was called with as a list, similar to C's argv, but without the app name itself (you get that in ''::[argv0]''). We don't need ''[argc]'' as we can always determine [[llength $argv]]. 

An example of making use of this variable is:

 #! /usr/local/bin/tclsh
 if { $::argc > 0 } {
        set i 1
        foreach arg $::argv {
                puts "argument $i is $arg"
                incr i
        }
  } else {
        puts "no command line argument passed"
  }


'''DGP''' -- It is true that we do not need ''::argc'', but
'''tclsh''' and '''wish''' and any application embedding Tcl
that calls ''Tcl_Main()'' provide it anyway.

[argv0] describes the name of the top-level script that was invoked via tclsh or wish.

http://purl.org/tcl/home/man/tcl8.3.2/UserCmd/tclsh.htm

http://purl.org/tcl/home/man/tcl8.3.2/UserCmd/wish.htm

Tk's Tk_ArgVInfo function makes a pass over the argv items, and handles some more arguments before placing the remainder in the argv list..

 
The arguments that these functions look for include:

   * -help      print out a usage statment
   * -colormap  specifies that the window should have a new private colormap
   * -display   specify the display and screen to use
   * -file      Ignored
   * -geometry  specify the location and size of the window
   * -name      used as title of the window and name of the interpreter
   * -sync      synchronous X server commands
   * -use       the main window of this app is to be embedded in another window
   * -visual    specify which visual to use for the window.


This seems to mean that you should not design your application to require flags of these names -
and even abbreviations of these!

----

See [command options] for a discussion of various options one has
in parsing the argv (and argv-like) information.

Also, note that [[[info script]]] describes the name of the currently executing script and this name even gets set by [source].
''Technically, it is set by Tcl_FSEvalFile(), for those using Tcl's C API.''

The command [[[info nameofexecutable]]] describes the name of the executing binary, and might be thought more like the C level argv[[0]].



Some code available that helps process the argv arguments include:

   * [clig (Kirsch)]
   * [CmdLine]

   * [evaluate_parameters]
 Where: ftp://ftp.Lehigh.EDU/pub/evap/evap-2.x/evap-2.2.tar.Z
        ftp://ftp.procplace.com/pub/tcl/sorted/packages-7.6/devel/evap-2.1.tar.gz
 Description: evaluate_parameters is a Perl program that
        processes command line arguments in a simple consistent manner
        performing type-checking, multi-levels of help, etc.
        generate_tk_program is an auxiliary program which generates
        a Tcl/Tk GUI wrapper around one's Perl or C program to gather
        the command line arguments interactively.
 Updated: 10/1999
 Contact: mailto:lusol@lehigh.edu (Stephen O. Lidie)

   * [ParseArgs]
   * [argp]
   * [argument parsing with defaults (Wagner)]
   * [argument processing for Tcl (Lehenbauer)]
   * [argument processing (Zimmer)]

   * [The Simple Library] [http://simplelib.bobsville.com] includes both a package for command arguments handling including typed arguments (with optional run-time checking) and options (SimpleProc, [http://simplelib.bobsville.com/packages/SimpleProc.txt]) and a very powerful command line options parser with too many features to list here  (SimpleOptions, [http://simplelib.bobsville.com/packages/SimpleOptions.txt]).

   * [sneaky_eval]
 Where: From the contact
 Description: Preprocess arguments before calling RecordAndEval or Eval,
        surrounding the arguments with braces so they won't be sub-evaluated.
 Updated:
 Contact: mailto:mdimeo@brooktree.com (Matt DiMeo)

   * [SNTL]
 Where: http://www.csua.berkeley.edu/%7Esls/woa/distrib/
        ftp://ftp.procplace.com/pub/tcl/sorted/packages-7.6/devel/sntl-0.4.2.tar.gz
        ftp://ftp.procplace.com/pub/tcl/sorted/packages-7.6/devel/sntl-0.4.2p1.patch.tar.gz
 Description: A general Tcl library of procedures.  Contains code to
        produce man pages from Tcl source, conversions from Tcl to C,
        HTML rendering, generating HTML, handling CGI forms, command line
        argument processing, a debugging message system, an object system,
        and various Tk widgets built with the object system.
 Updated: 10/1998
 Contact: mailto:slshen@lbl.gov (Sam Shen)
        mailto:sls@aero.org (Sam Shen)

   * [variable argument process]
   * [yaap - Yet Another Argument Parsing utility]
   * [command options]

----
Schelte Bron wrote in [the comp.lang.tcl newsgroup] on 2004-02-19: ''I sometimes use numbers as variable names for a list of arguments like argv in the main script or args inside a proc.''

 set i 0; foreach n $argv {set [incr i] $n}

''I can then refer to the arguments as $1, $2, etc. just like in sh/ksh/bash.''

[rdt] Uhh, can't you just have the proc use those name?  i.e.
 proc xyz {1 2 3} {
   # use the args as:
   puts "1=$1, 2=$2, 3=$3"
 }
What's wrong with that if that is what you want?

[sbron] There's nothing wrong with that, in a different situation. The point was having easy access to an unknown number of arguments.

[rdt] I see.  Yes that is additional capability, thanks.

[MG] adds that (especially when you're doing it outside a proc, and so the variables are all persistant) you should add an 'unset i n' to the end of the code above, just to clean up properly.
----
[Tcl syntax help] -
[Arts and Crafts of Tcl-Tk Programming] -
[Category Argument Processing]