/usr/share/calc/custhelp/argv is in apcalc-common 2.12.4.4-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 | NAME
    argv - displays information about its args
SYNOPSIS
    custom("argv" [, arg ...])
TYPES
    arg		any
    return	int
DESCRIPTION
    This custom function will, for each arg given print:
	arg number
	arg type
	number of elements (size())
	memory size (sizeof())
    The number of args passed, not counting the initial "argv" name
    arg is returned.
EXAMPLE
    > foo=5^713; bar=17; baz=list(2,3,4);
    > custom("argv", foo, bar, baz, 3+4.5i, pi())
	    arg[0]  rational_value	    size=1  sizeof=272
	    arg[1]  rational_value	    size=1  sizeof=68
	    arg[2]  list		    size=3  sizeof=256
	    arg[3]  complex_value	    size=1  sizeof=140
	    arg[4]  rational_value	    size=1  sizeof=84
	    5
LIMITS
    calc must be built with ALLOW_CUSTOM= -DCUSTOM
    calc must be executed with a -C arg.
LIBRARY
    none
SEE ALSO
    custom
## Copyright (C) 1999  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
##
## @(#) $Revision: 30.1 $
## @(#) $Id: argv,v 30.1 2007/03/16 11:10:04 chongo Exp $
## @(#) $Source: /usr/local/src/cmd/calc/custom/RCS/argv,v $
##
## Under source code control:	1997/03/09 20:28:01
## File existed as early as:	1997
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/
 |