NAME
    errno - return or set a stored error-number

SYNOPSIS
    errno([errnum])

TYPES
    errnum	integer

    return	integer

DESCRIPTION
    Whenever an operation or evaluation of function returns an error-value,
    the numerical code for that value is stored as "global calc_errno value".

    The term "global calc_errno value" is an internal calc state.
    This is NOT a calc variable called calc_errno.

    NOTE:

	The errno() builtin should not be confused with the errno
	used by libc in C.  The range of errnum extend beyond the
	C's libc errno.  See help error for information on the mean
	of various errnum ranges.

    Unlike error() calling errno() does NOT increment the global
    calc error count (see help errcount).

    errno() returns the current value of "global calc_errno value".
    Unlike error() calling errno() does NOT increment the global
    calc error count (see help errcount).

    errno(errnum) sets "global calc_errno value" to the value errnum
    and returns its previous value.  Unlike error(errnum) calling
    errno(errnum) does NOT increment the global calc error count
    (see help errcount).

    To detect whether an error occurs during some sequence of operations,
    one may immediately before that sequence set the stored error-number
    to zero by errno(0), and then after the operations, whether or not
    an error has occurred will be indicated by errno() being nonzero or
    zero.  If a non-zero value is returned, that value will be the code
    for the most recent error encountered.

    The default argument for the functions error() and strerror() is the
    currently stored error-number; in particular, if no error-value has
    been returned after the last errno(0), strerror() will return
    "No error".

EXAMPLE
    ; ## Assuming there is no file with name "not_a_file"

    ; errcount(0),; errmax(20),;
    ; print errcount(), errmax()
    0 20

    ; badfile = fopen("not_a_file", "r")
    ; print errcount(), errno(), strerror()
    1 2 No such file or directory

    ; a = 1/0
    ; print errcount(), errno(), strerror()
    2 10001 Division by zero

LIMITS
    0 <= errnum <= 32767

LINK LIBRARY
    int calc_errno;	/* global calc_errno value */

SEE ALSO
    errmax, errcount, error, strerror, iserror, newerror, errorcodes,
    stoponerror

## Copyright (C) 1999-2006,2021,2023  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.
##
## Under source code control:	1994/10/27 03:05:08
## File existed as early as:	1994
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/