argc is a global [namespace] [Tcl] variable set by [tclsh], [wish] and other code doing similar setup.

It contains a count of the number of arguments passed to the command upon invocation.

The count begins at 1, and the count does not include the name of the script itself (which in [tclsh] can be found in [argv0]) 
(both of which is different from C's argc).

======
# program usage requires at least one argument
if { $::argc eq 0 } {
   puts "USAGE: $::argv0 argument"
   exit 1
}

======

See also: [argv]

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[Tcl syntax]
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