Updated 2013-11-28 18:23:21 by pooryorick

$argv is a global variable provided by tclsh and wish mainline code (and NOT the tcl or tk libraries).

See Also  edit

command options

Description  edit

$argv contains the arguments the app was called with as a list, similar to C's argv, but without the app name itself, which is stored in $::argv0. While argc exists, we don't really need it since 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. Also, new child interpreters don't get argc and argv set by default - set them if they need them.

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

tclsh man page: wish man page:

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

This means that you should not design your application to require flags of these names or even abbreviations of these! Otherwise, The argvinfo function in Tk grabs them before your application finds them.

RS 2013-10-08 - If you don't need the Tk options, but want to preserve your argv (where maybe -n xx would be consumed as matching -name), in scripts with the tclsh executable it helps to do
 set argv [linsert $argv 0 --]
 package require Tk

When wish is the executable, you can only write the "--" flag explicitly, or define a shell alias:
 $ alias wish='wish --'

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:

 Where: ftp://ftp.Lehigh.EDU/pub/evap/evap-2.x/evap-2.2.tar.Z
 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:[email protected] (Stephen O. Lidie)

 Where: From the contact
 Description: Preprocess arguments before calling RecordAndEval or Eval,
        surrounding the arguments with braces so they won't be sub-evaluated.
 Contact: mailto:[email protected] (Matt DiMeo)

  • SNTL[5]
 Where: http://www.csua.berkeley.edu/%7Esls/woa/distrib/
 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:[email protected] (Sam Shen)
        mailto:[email protected] (Sam Shen)

Schelte Bron wrote in comp.lang.tcl 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.