/*
 * *****************************************************************************
 *
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2018-2025 Gavin D. Howard and contributors.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
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 *   list of conditions and the following disclaimer.
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 *   this list of conditions and the following disclaimer in the documentation
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 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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 * *****************************************************************************
 *
 * The dc help text.
 *
 */

usage: %s [options] [file...]

dc is a reverse-polish notation command-line calculator which supports unlimited
precision arithmetic. For details, use `man %s` or see the online documentation
at https://github.com/gavinhoward/bc/tree/%s/manuals/dc/%s.1.md .

This dc is (mostly) compatible with the OpenBSD dc and the GNU dc. See the
OpenBSD man page (http://man.openbsd.org/OpenBSD-current/man1/dc.1) and the GNU
dc manual (https://www.gnu.org/software/bc/manual/dc-1.05/html_mono/dc.html)
for details.

This dc has a few differences from the two above:

  1) When printing a byte stream (command "P"), this bc follows what the FreeBSD
     dc does.
  2) This dc implements the GNU extensions for divmod ("~") and modular
     exponentiation ("|").
  3) This dc implements all FreeBSD extensions, except for "J" and "M".
  4) This dc does not implement the run command ("!"), for security reasons.
  5) Like the FreeBSD dc, this dc supports extended registers. However, they are
     implemented differently. When it encounters whitespace where a register
     should be, it skips the whitespace. If the character following is not
     a lowercase letter, an error is issued. Otherwise, the register name is
     parsed by the following regex:

       [a-z][a-z0-9_]*

     This generally means that register names will be surrounded by whitespace.

     Examples:

       l idx s temp L index S temp2 < do_thing

     Also note that, unlike the FreeBSD dc, extended registers are not even
     parsed unless the "-x" option is given. Instead, the space after a command
     that requires a register name is taken as the register name.

Options:

  -C  --no-digit-clamp

      Disables clamping of digits that are larger than or equal to the current
      ibase when parsing numbers.

      This means that the value added to a number from a digit is always that
      digit's value multiplied by the value of ibase raised to the power of the
      digit's position, which starts from 0 at the least significant digit.

      If multiple of this option and the -c option are given, the last is used.

  -c  --digit-clamp

      Enables clamping of digits that are larger than or equal to the current
      ibase when parsing numbers.

      This means that digits that the value added to a number from a digit that
      is greater than or equal to the ibase is the value of ibase minus 1 all
      multiplied by the value of ibase raised to the power of the digit's
      position, which starts from 0 at the least significant digit.

      If multiple of this option and the -C option are given, the last is used.
{{ A H N HN }}

  -E  seed  --seed=seed

      Sets the builtin variable seed to the given value assuming that the given
      value is in base 10. It is a fatal error if the given value is not a valid
      number.
{{ end }}

  -e  expr  --expression=expr

      Run "expr" and quit. If multiple expressions or files (see below) are
      given, they are all run. After running, dc will exit.

  -f  file  --file=file

      Run the dc code in "file" and exit. See above.

  -h  --help

      Print this usage message and exit.

  -I  ibase  --ibase=ibase

      Sets the builtin variable ibase to the given value assuming that the given
      value is in base 10. It is a fatal error if the given value is not a valid
      number.

  -i  --interactive

      Put dc into interactive mode. See the man page for more details.

  -L  --no-line-length

      Disable line length checking.

  -O  obase  --obase=obase

      Sets the builtin variable obase to the given value assuming that the given
      value is in base 10. It is a fatal error if the given value is not a valid
      number.

  -P  --no-prompt

      Disable the prompts in interactive mode.

  -R  --no-read-prompt

      Disable the read prompt in interactive mode.

  -S  scale  --scale=scale

      Sets the builtin variable scale to the given value assuming that the given
      value is in base 10. It is a fatal error if the given value is not a valid
      number.

  -V  --version

      Print version and copyright and exit.

  -x  --extended-register

      Enable extended register mode.

  -z  --leading-zeroes

      Enable leading zeroes on numbers greater than -1 and less than 1.

Environment variables:

  DC_ENV_ARGS

      Command-line arguments to use on every run.

  DC_LINE_LENGTH

      If an integer, the number of characters to print on a line before
      wrapping. Using 0 will disable line length checking.

  DC_SIGINT_RESET

      If an integer and non-zero, reset on SIGINT, rather than exit, when in
      interactive mode.

      If zero, do not reset on SIGINT in all cases, but exit instead.

      Overrides the default, which is %s.

  DC_TTY_MODE

      If an integer and non-zero, enable TTY mode when it is available.

      If zero, disable TTY mode in all cases.

      Overrides the default, which is TTY mode %s.

  DC_PROMPT

      If an integer and non-zero, enable prompt when TTY mode is possible.

      If zero, disable prompt in all cases.

      Overrides the default, which is prompt %s.

  DC_EXPR_EXIT

      If an integer and non-zero, exit when expressions or expression files are
      given on the command-line, and does not exit when an integer and zero.

      Overrides the default, which is %s.

  DC_DIGIT_CLAMP

      If an integer and non-zero, clamp digits larger than or equal to the
      current ibase when parsing numbers.

      Overrides the default, which is %s.
