3 SPDX-License-Identifier: BSD-2-Clause
5 Copyright (c) 2018-2021 Gavin D. Howard and contributors.
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8 modification, are permitted provided that the following conditions are met:
10 * Redistributions of source code must retain the above copyright notice, this
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33 dc - arbitrary-precision decimal reverse-Polish notation calculator
37 **dc** [**-hiPvVx**] [**--version**] [**--help**] [**--interactive**] [**--no-prompt**] [**--extended-register**] [**-e** *expr*] [**--expression**=*expr*...] [**-f** *file*...] [**-file**=*file*...] [*file*...]
41 dc(1) is an arbitrary-precision calculator. It uses a stack (reverse Polish
42 notation) to store numbers and results of computations. Arithmetic operations
43 pop arguments off of the stack and push the results.
45 If no files are given on the command-line as extra arguments (i.e., not as
46 **-f** or **--file** arguments), then dc(1) reads from **stdin**. Otherwise,
47 those files are processed, and dc(1) will then exit.
49 This is different from the dc(1) on OpenBSD and possibly other dc(1)
50 implementations, where **-e** (**--expression**) and **-f** (**--file**)
51 arguments cause dc(1) to execute them and exit. The reason for this is that this
52 dc(1) allows users to set arguments in the environment variable **DC_ENV_ARGS**
53 (see the **ENVIRONMENT VARIABLES** section). Any expressions given on the
54 command-line should be used to set up a standard environment. For example, if a
55 user wants the **scale** always set to **10**, they can set **DC_ENV_ARGS** to
56 **-e 10k**, and this dc(1) will always start with a **scale** of **10**.
58 If users want to have dc(1) exit after processing all input from **-e** and
59 **-f** arguments (and their equivalents), then they can just simply add **-e q**
60 as the last command-line argument or define the environment variable
65 The following are the options that dc(1) accepts.
69 : Prints a usage message and quits.
71 **-v**, **-V**, **--version**
73 : Print the version information (copyright header) and exit.
75 **-i**, **--interactive**
77 : Forces interactive mode. (See the **INTERACTIVE MODE** section.)
79 This is a **non-portable extension**.
81 **-P**, **--no-prompt**
83 {{ A E H N EH EN HN EHN }}
84 : Disables the prompt in TTY mode. (The prompt is only enabled in TTY mode.
85 See the **TTY MODE** section) This is mostly for those users that do not
86 want a prompt or are not used to having them in dc(1). Most of those users
87 would want to put this option in **DC_ENV_ARGS**.
89 {{ P EP HP NP EHP ENP HNP EHNP }}
90 : This option is a no-op.
93 This is a **non-portable extension**.
95 **-x** **--extended-register**
97 : Enables extended register mode. See the *Extended Register Mode* subsection
98 of the **REGISTERS** section for more information.
100 This is a **non-portable extension**.
102 **-e** *expr*, **--expression**=*expr*
104 : Evaluates *expr*. If multiple expressions are given, they are evaluated in
105 order. If files are given as well (see below), the expressions and files are
106 evaluated in the order given. This means that if a file is given before an
107 expression, the file is read in and evaluated first.
109 After processing all expressions and files, dc(1) will exit, unless **-**
110 (**stdin**) was given as an argument at least once to **-f** or **--file**.
112 This is a **non-portable extension**.
114 **-f** *file*, **--file**=*file*
116 : Reads in *file* and evaluates it, line by line, as though it were read
117 through **stdin**. If expressions are also given (see above), the
118 expressions are evaluated in the order given.
120 After processing all expressions and files, dc(1) will exit, unless **-**
121 (**stdin**) was given as an argument at least once to **-f** or **--file**.
122 However, if any other **-e**, **--expression**, **-f**, or **--file**
123 arguments are given after that, bc(1) will give a fatal error and exit.
125 This is a **non-portable extension**.
127 All long options are **non-portable extensions**.
131 Any non-error output is written to **stdout**.
133 **Note**: Unlike other dc(1) implementations, this dc(1) will issue a fatal
134 error (see the **EXIT STATUS** section) if it cannot write to **stdout**, so if
135 **stdout** is closed, as in **dc <file> >&-**, it will quit with an error. This
136 is done so that dc(1) can report problems when **stdout** is redirected to a
139 If there are scripts that depend on the behavior of other dc(1) implementations,
140 it is recommended that those scripts be changed to redirect **stdout** to
145 Any error output is written to **stderr**.
147 **Note**: Unlike other dc(1) implementations, this dc(1) will issue a fatal
148 error (see the **EXIT STATUS** section) if it cannot write to **stderr**, so if
149 **stderr** is closed, as in **dc <file> 2>&-**, it will quit with an error. This
150 is done so that dc(1) can exit with an error code when **stderr** is redirected
153 If there are scripts that depend on the behavior of other dc(1) implementations,
154 it is recommended that those scripts be changed to redirect **stderr** to
159 Each item in the input source code, either a number (see the **NUMBERS**
160 section) or a command (see the **COMMANDS** section), is processed and executed,
161 in order. Input is processed immediately when entered.
163 **ibase** is a register (see the **REGISTERS** section) that determines how to
164 interpret constant numbers. It is the "input" base, or the number base used for
165 interpreting input numbers. **ibase** is initially **10**. The max allowable
166 value for **ibase** is **16**. The min allowable value for **ibase** is **2**.
167 The max allowable value for **ibase** can be queried in dc(1) programs with the
170 **obase** is a register (see the **REGISTERS** section) that determines how to
171 output results. It is the "output" base, or the number base used for outputting
172 numbers. **obase** is initially **10**. The max allowable value for **obase** is
173 **DC_BASE_MAX** and can be queried with the **U** command. The min allowable
174 {{ A H N P HN HP NP HNP }}
175 value for **obase** is **0**. If **obase** is **0**, values are output in
176 scientific notation, and if **obase** is **1**, values are output in engineering
177 notation. Otherwise, values are output in the specified base.
179 Outputting in scientific and engineering notations are **non-portable
182 {{ E EH EN EP EHN EHP ENP EHNP }}
183 value for **obase** is **2**. Values are output in the specified base.
186 The *scale* of an expression is the number of digits in the result of the
187 expression right of the decimal point, and **scale** is a register (see the
188 **REGISTERS** section) that sets the precision of any operations (with
189 exceptions). **scale** is initially **0**. **scale** cannot be negative. The max
190 allowable value for **scale** can be queried in dc(1) programs with the **V**
193 {{ A H N P HN HP NP HNP }}
194 **seed** is a register containing the current seed for the pseudo-random number
195 generator. If the current value of **seed** is queried and stored, then if it is
196 assigned to **seed** later, the pseudo-random number generator is guaranteed to
197 produce the same sequence of pseudo-random numbers that were generated after the
198 value of **seed** was first queried.
200 Multiple values assigned to **seed** can produce the same sequence of
201 pseudo-random numbers. Likewise, when a value is assigned to **seed**, it is not
202 guaranteed that querying **seed** immediately after will return the same value.
203 In addition, the value of **seed** will change after any call to the **'**
204 command or the **"** command that does not get receive a value of **0** or
205 **1**. The maximum integer returned by the **'** command can be queried with the
208 **Note**: The values returned by the pseudo-random number generator with the
209 **'** and **"** commands are guaranteed to **NOT** be cryptographically secure.
210 This is a consequence of using a seeded pseudo-random number generator. However,
211 they *are* guaranteed to be reproducible with identical **seed** values. This
212 means that the pseudo-random values from bc(1) should only be used where a
213 reproducible stream of pseudo-random numbers is *ESSENTIAL*. In any other case,
214 use a non-seeded pseudo-random number generator.
216 The pseudo-random number generator, **seed**, and all associated operations are
217 **non-portable extensions**.
222 Comments go from **#** until, and not including, the next newline. This is a
223 **non-portable extension**.
227 Numbers are strings made up of digits, uppercase letters up to **F**, and at
228 most **1** period for a radix. Numbers can have up to **DC_NUM_MAX** digits.
229 Uppercase letters are equal to **9** + their position in the alphabet (i.e.,
230 **A** equals **10**, or **9+1**). If a digit or letter makes no sense with the
231 current value of **ibase**, they are set to the value of the highest valid digit
234 Single-character numbers (i.e., **A** alone) take the value that they would have
235 if they were valid digits, regardless of the value of **ibase**. This means that
236 **A** alone always equals decimal **10** and **F** alone always equals decimal
239 {{ A H N P HN HP NP HNP }}
240 In addition, dc(1) accepts numbers in scientific notation. These have the form
241 **\<number\>e\<integer\>**. The exponent (the portion after the **e**) must be
242 an integer. An example is **1.89237e9**, which is equal to **1892370000**.
243 Negative exponents are also allowed, so **4.2890e_3** is equal to **0.0042890**.
245 **WARNING**: Both the number and the exponent in scientific notation are
246 interpreted according to the current **ibase**, but the number is still
247 multiplied by **10\^exponent** regardless of the current **ibase**. For example,
248 if **ibase** is **16** and dc(1) is given the number string **FFeA**, the
249 resulting decimal number will be **2550000000000**, and if dc(1) is given the
250 number string **10e_4**, the resulting decimal number will be **0.0016**.
252 Accepting input as scientific notation is a **non-portable extension**.
257 The valid commands are listed below.
261 These commands are used for printing.
263 {{ A H N P HN HP NP HNP }}
264 Note that both scientific notation and engineering notation are available for
265 printing numbers. Scientific notation is activated by assigning **0** to
266 **obase** using **0o**, and engineering notation is activated by assigning **1**
267 to **obase** using **1o**. To deactivate them, just assign a different value to
270 Printing numbers in scientific notation and/or engineering notation is a
271 **non-portable extension**.
276 : Prints the value on top of the stack, whether number or string, and prints a
279 This does not alter the stack.
283 : Prints the value on top of the stack, whether number or string, and pops it
288 : Pops a value off the stack.
290 If the value is a number, it is truncated and the absolute value of the
291 result is printed as though **obase** is **UCHAR_MAX+1** and each digit is
292 interpreted as an ASCII character, making it a byte stream.
294 If the value is a string, it is printed without a trailing newline.
296 This is a **non-portable extension**.
300 : Prints the entire contents of the stack, in order from newest to oldest,
301 without altering anything.
303 Users should use this command when they get lost.
307 These are the commands used for arithmetic.
311 : The top two values are popped off the stack, added, and the result is pushed
312 onto the stack. The *scale* of the result is equal to the max *scale* of
317 : The top two values are popped off the stack, subtracted, and the result is
318 pushed onto the stack. The *scale* of the result is equal to the max
319 *scale* of both operands.
323 : The top two values are popped off the stack, multiplied, and the result is
324 pushed onto the stack. If **a** is the *scale* of the first expression and
325 **b** is the *scale* of the second expression, the *scale* of the result
326 is equal to **min(a+b,max(scale,a,b))** where **min()** and **max()** return
331 : The top two values are popped off the stack, divided, and the result is
332 pushed onto the stack. The *scale* of the result is equal to **scale**.
334 The first value popped off of the stack must be non-zero.
338 : The top two values are popped off the stack, remaindered, and the result is
339 pushed onto the stack.
341 Remaindering is equivalent to 1) Computing **a/b** to current **scale**, and
342 2) Using the result of step 1 to calculate **a-(a/b)\*b** to *scale*
343 **max(scale+scale(b),scale(a))**.
345 The first value popped off of the stack must be non-zero.
349 : The top two values are popped off the stack, divided and remaindered, and
350 the results (divided first, remainder second) are pushed onto the stack.
351 This is equivalent to **x y / x y %** except that **x** and **y** are only
354 The first value popped off of the stack must be non-zero.
356 This is a **non-portable extension**.
360 : The top two values are popped off the stack, the second is raised to the
361 power of the first, and the result is pushed onto the stack. The *scale* of
362 the result is equal to **scale**.
364 The first value popped off of the stack must be an integer, and if that
365 value is negative, the second value popped off of the stack must be
370 : The top value is popped off the stack, its square root is computed, and the
371 result is pushed onto the stack. The *scale* of the result is equal to
374 The value popped off of the stack must be non-negative.
378 : If this command *immediately* precedes a number (i.e., no spaces or other
379 commands), then that number is input as a negative number.
381 Otherwise, the top value on the stack is popped and copied, and the copy is
382 negated and pushed onto the stack. This behavior without a number is a
383 **non-portable extension**.
387 : The top value is popped off the stack, and if it is zero, it is pushed back
388 onto the stack. Otherwise, its absolute value is pushed onto the stack.
390 This is a **non-portable extension**.
394 : The top three values are popped off the stack, a modular exponentiation is
395 computed, and the result is pushed onto the stack.
397 The first value popped is used as the reduction modulus and must be an
398 integer and non-zero. The second value popped is used as the exponent and
399 must be an integer and non-negative. The third value popped is the base and
402 This is a **non-portable extension**.
404 {{ A H N P HN HP NP HNP }}
407 : The top value is popped off the stack and copied, and the copy is truncated
408 and pushed onto the stack.
410 This is a **non-portable extension**.
414 : The top two values are popped off the stack, and the precision of the second
415 is set to the value of the first, whether by truncation or extension.
417 The first value popped off of the stack must be an integer and non-negative.
419 This is a **non-portable extension**.
423 : The top two values are popped off the stack, and the second is shifted left
424 (radix shifted right) to the value of the first.
426 The first value popped off of the stack must be an integer and non-negative.
428 This is a **non-portable extension**.
432 : The top two values are popped off the stack, and the second is shifted right
433 (radix shifted left) to the value of the first.
435 The first value popped off of the stack must be an integer and non-negative.
437 This is a **non-portable extension**.
442 : The top two values are popped off of the stack, they are compared, and a
443 **1** is pushed if they are equal, or **0** otherwise.
445 This is a **non-portable extension**.
449 : The top value is popped off of the stack, and if it a **0**, a **1** is
450 pushed; otherwise, a **0** is pushed.
452 This is a **non-portable extension**.
456 : The top two values are popped off of the stack, they are compared, and a
457 **1** is pushed if the first is less than the second, or **0** otherwise.
459 This is a **non-portable extension**.
463 : The top two values are popped off of the stack, they are compared, and a
464 **1** is pushed if the first is less than or equal to the second, or **0**
467 This is a **non-portable extension**.
471 : The top two values are popped off of the stack, they are compared, and a
472 **1** is pushed if the first is greater than the second, or **0** otherwise.
474 This is a **non-portable extension**.
478 : The top two values are popped off of the stack, they are compared, and a
479 **1** is pushed if the first is greater than or equal to the second, or
482 This is a **non-portable extension**.
486 : The top two values are popped off of the stack. If they are both non-zero, a
487 **1** is pushed onto the stack. If either of them is zero, or both of them
488 are, then a **0** is pushed onto the stack.
490 This is like the **&&** operator in bc(1), and it is *not* a short-circuit
493 This is a **non-portable extension**.
497 : The top two values are popped off of the stack. If at least one of them is
498 non-zero, a **1** is pushed onto the stack. If both of them are zero, then a
499 **0** is pushed onto the stack.
501 This is like the **||** operator in bc(1), and it is *not* a short-circuit
504 This is a **non-portable extension**.
506 {{ A H N P HN HP NP HNP }}
507 ## Pseudo-Random Number Generator
509 dc(1) has a built-in pseudo-random number generator. These commands query the
510 pseudo-random number generator. (See Parameters for more information about the
511 **seed** value that controls the pseudo-random number generator.)
513 The pseudo-random number generator is guaranteed to **NOT** be
514 cryptographically secure.
518 : Generates an integer between 0 and **DC_RAND_MAX**, inclusive (see the
521 The generated integer is made as unbiased as possible, subject to the
522 limitations of the pseudo-random number generator.
524 This is a **non-portable extension**.
528 : Pops a value off of the stack, which is used as an **exclusive** upper bound
529 on the integer that will be generated. If the bound is negative or is a
530 non-integer, an error is raised, and dc(1) resets (see the **RESET**
531 section) while **seed** remains unchanged. If the bound is larger than
532 **DC_RAND_MAX**, the higher bound is honored by generating several
533 pseudo-random integers, multiplying them by appropriate powers of
534 **DC_RAND_MAX+1**, and adding them together. Thus, the size of integer that
535 can be generated with this command is unbounded. Using this command will
536 change the value of **seed**, unless the operand is **0** or **1**. In that
537 case, **0** is pushed onto the stack, and **seed** is *not* changed.
539 The generated integer is made as unbiased as possible, subject to the
540 limitations of the pseudo-random number generator.
542 This is a **non-portable extension**.
547 These commands control the stack.
551 : Removes all items from ("clears") the stack.
555 : Copies the item on top of the stack ("duplicates") and pushes the copy onto
560 : Swaps ("reverses") the two top items on the stack.
564 : Pops ("removes") the top value from the stack.
568 These commands control registers (see the **REGISTERS** section).
572 : Pops the value off the top of the stack and stores it into register *r*.
576 : Copies the value in register *r* and pushes it onto the stack. This does not
577 alter the contents of *r*.
581 : Pops the value off the top of the (main) stack and pushes it onto the stack
582 of register *r*. The previous value of the register becomes inaccessible.
586 : Pops the value off the top of the stack for register *r* and push it onto
587 the main stack. The previous value in the stack for register *r*, if any, is
588 now accessible via the **l***r* command.
592 {{ A H N P HN HP NP HNP }}
593 These commands control the values of **ibase**, **obase**, **scale**, and
594 **seed**. Also see the **SYNTAX** section.
596 {{ E EH EN EP EHN EHP ENP EHNP }}
597 These commands control the values of **ibase**, **obase**, and **scale**. Also
598 see the **SYNTAX** section.
603 : Pops the value off of the top of the stack and uses it to set **ibase**,
604 which must be between **2** and **16**, inclusive.
606 If the value on top of the stack has any *scale*, the *scale* is ignored.
610 : Pops the value off of the top of the stack and uses it to set **obase**,
611 {{ A H N P HN HP NP HNP }}
612 which must be between **0** and **DC_BASE_MAX**, inclusive (see the
613 **LIMITS** section and the **NUMBERS** section).
615 {{ E EH EN EP EHN EHP ENP EHNP }}
616 which must be between **2** and **DC_BASE_MAX**, inclusive (see the
620 If the value on top of the stack has any *scale*, the *scale* is ignored.
624 : Pops the value off of the top of the stack and uses it to set **scale**,
625 which must be non-negative.
627 If the value on top of the stack has any *scale*, the *scale* is ignored.
629 {{ A H N P HN HP NP HNP }}
632 : Pops the value off of the top of the stack and uses it to set **seed**. The
633 meaning of **seed** is dependent on the current pseudo-random number
634 generator but is guaranteed to not change except for new major versions.
636 The *scale* and sign of the value may be significant.
638 If a previously used **seed** value is used again, the pseudo-random number
639 generator is guaranteed to produce the same sequence of pseudo-random
640 numbers as it did when the **seed** value was previously used.
642 The exact value assigned to **seed** is not guaranteed to be returned if the
643 **J** command is used. However, if **seed** *does* return a different value,
644 both values, when assigned to **seed**, are guaranteed to produce the same
645 sequence of pseudo-random numbers. This means that certain values assigned
646 to **seed** will not produce unique sequences of pseudo-random numbers.
648 There is no limit to the length (number of significant decimal digits) or
649 *scale* of the value that can be assigned to **seed**.
651 This is a **non-portable extension**.
656 : Pushes the current value of **ibase** onto the main stack.
660 : Pushes the current value of **obase** onto the main stack.
664 : Pushes the current value of **scale** onto the main stack.
666 {{ A H N P HN HP NP HNP }}
669 : Pushes the current value of **seed** onto the main stack.
671 This is a **non-portable extension**.
676 : Pushes the maximum allowable value of **ibase** onto the main stack.
678 This is a **non-portable extension**.
682 : Pushes the maximum allowable value of **obase** onto the main stack.
684 This is a **non-portable extension**.
688 : Pushes the maximum allowable value of **scale** onto the main stack.
690 This is a **non-portable extension**.
692 {{ A H N P HN HP NP HNP }}
695 : Pushes the maximum (inclusive) integer that can be generated with the **'**
696 pseudo-random number generator command.
698 This is a **non-portable extension**.
703 The following commands control strings.
705 dc(1) can work with both numbers and strings, and registers (see the
706 **REGISTERS** section) can hold both strings and numbers. dc(1) always knows
707 whether the contents of a register are a string or a number.
709 While arithmetic operations have to have numbers, and will print an error if
710 given a string, other commands accept strings.
712 Strings can also be executed as macros. For example, if the string **[1pR]** is
713 executed as a macro, then the code **1pR** is executed, meaning that the **1**
714 will be printed with a newline after and then popped from the stack.
716 **\[**_characters_**\]**
718 : Makes a string containing *characters* and pushes it onto the stack.
720 If there are brackets (**\[** and **\]**) in the string, then they must be
721 balanced. Unbalanced brackets can be escaped using a backslash (**\\**)
724 If there is a backslash character in the string, the character after it
725 (even another backslash) is put into the string verbatim, but the (first)
730 : The value on top of the stack is popped.
732 If it is a number, it is truncated and its absolute value is taken. The
733 result mod **UCHAR_MAX+1** is calculated. If that result is **0**, push an
734 empty string; otherwise, push a one-character string where the character is
735 the result of the mod interpreted as an ASCII character.
737 If it is a string, then a new string is made. If the original string is
738 empty, the new string is empty. If it is not, then the first character of
739 the original string is used to create the new string as a one-character
740 string. The new string is then pushed onto the stack.
742 This is a **non-portable extension**.
746 : Pops a value off of the top of the stack.
748 If it is a number, it is pushed back onto the stack.
750 If it is a string, it is executed as a macro.
752 This behavior is the norm whenever a macro is executed, whether by this
753 command or by the conditional execution commands below.
757 : Pops two values off of the stack that must be numbers and compares them. If
758 the first value is greater than the second, then the contents of register
761 For example, **0 1>a** will execute the contents of register **a**, and
764 If either or both of the values are not numbers, dc(1) will raise an error
765 and reset (see the **RESET** section).
769 : Like the above, but will execute register *s* if the comparison fails.
771 If either or both of the values are not numbers, dc(1) will raise an error
772 and reset (see the **RESET** section).
774 This is a **non-portable extension**.
778 : Pops two values off of the stack that must be numbers and compares them. If
779 the first value is not greater than the second (less than or equal to), then
780 the contents of register *r* are executed.
782 If either or both of the values are not numbers, dc(1) will raise an error
783 and reset (see the **RESET** section).
787 : Like the above, but will execute register *s* if the comparison fails.
789 If either or both of the values are not numbers, dc(1) will raise an error
790 and reset (see the **RESET** section).
792 This is a **non-portable extension**.
796 : Pops two values off of the stack that must be numbers and compares them. If
797 the first value is less than the second, then the contents of register *r*
800 If either or both of the values are not numbers, dc(1) will raise an error
801 and reset (see the **RESET** section).
805 : Like the above, but will execute register *s* if the comparison fails.
807 If either or both of the values are not numbers, dc(1) will raise an error
808 and reset (see the **RESET** section).
810 This is a **non-portable extension**.
814 : Pops two values off of the stack that must be numbers and compares them. If
815 the first value is not less than the second (greater than or equal to), then
816 the contents of register *r* are executed.
818 If either or both of the values are not numbers, dc(1) will raise an error
819 and reset (see the **RESET** section).
823 : Like the above, but will execute register *s* if the comparison fails.
825 If either or both of the values are not numbers, dc(1) will raise an error
826 and reset (see the **RESET** section).
828 This is a **non-portable extension**.
832 : Pops two values off of the stack that must be numbers and compares them. If
833 the first value is equal to the second, then the contents of register *r*
836 If either or both of the values are not numbers, dc(1) will raise an error
837 and reset (see the **RESET** section).
841 : Like the above, but will execute register *s* if the comparison fails.
843 If either or both of the values are not numbers, dc(1) will raise an error
844 and reset (see the **RESET** section).
846 This is a **non-portable extension**.
850 : Pops two values off of the stack that must be numbers and compares them. If
851 the first value is not equal to the second, then the contents of register
854 If either or both of the values are not numbers, dc(1) will raise an error
855 and reset (see the **RESET** section).
859 : Like the above, but will execute register *s* if the comparison fails.
861 If either or both of the values are not numbers, dc(1) will raise an error
862 and reset (see the **RESET** section).
864 This is a **non-portable extension**.
868 : Reads a line from the **stdin** and executes it. This is to allow macros to
869 request input from users.
873 : During execution of a macro, this exits the execution of that macro and the
874 execution of the macro that executed it. If there are no macros, or only one
875 macro executing, dc(1) exits.
879 : Pops a value from the stack which must be non-negative and is used the
880 number of macro executions to pop off of the execution stack. If the number
881 of levels to pop is greater than the number of executing macros, dc(1)
886 These commands query status of the stack or its top value.
890 : Pops a value off of the stack.
892 If it is a number, calculates the number of significant decimal digits it
893 has and pushes the result.
895 If it is a string, pushes the number of characters the string has.
899 : Pops a value off of the stack.
901 If it is a number, pushes the *scale* of the value onto the stack.
903 If it is a string, pushes **0**.
907 : Pushes the current stack depth (before execution of this command).
911 These commands manipulate arrays.
915 : Pops the top two values off of the stack. The second value will be stored in
916 the array *r* (see the **REGISTERS** section), indexed by the first value.
920 : Pops the value on top of the stack and uses it as an index into the array
921 *r*. The selected value is then pushed onto the stack.
925 Registers are names that can store strings, numbers, and arrays. (Number/string
926 registers do not interfere with array registers.)
928 Each register is also its own stack, so the current register value is the top of
929 the stack for the register. All registers, when first referenced, have one value
930 (**0**) in their stack.
932 In non-extended register mode, a register name is just the single character that
933 follows any command that needs a register name. The only exception is a newline
934 (**'\\n'**); it is a parse error for a newline to be used as a register name.
936 ## Extended Register Mode
938 Unlike most other dc(1) implentations, this dc(1) provides nearly unlimited
939 amounts of registers, if extended register mode is enabled.
941 If extended register mode is enabled (**-x** or **--extended-register**
942 command-line arguments are given), then normal single character registers are
943 used *unless* the character immediately following a command that needs a
944 register name is a space (according to **isspace()**) and not a newline
947 In that case, the register name is found according to the regex
948 **\[a-z\]\[a-z0-9\_\]\*** (like bc(1) identifiers), and it is a parse error if
949 the next non-space characters do not match that regex.
953 When dc(1) encounters an error or a signal that it has a non-default handler
954 for, it resets. This means that several things happen.
956 First, any macros that are executing are stopped and popped off the stack.
957 The behavior is not unlike that of exceptions in programming languages. Then
958 the execution point is set so that any code waiting to execute (after all
959 macros returned) is skipped.
961 Thus, when dc(1) resets, it skips any remaining code waiting to be executed.
962 Then, if it is interactive mode, and the error was not a fatal error (see the
963 **EXIT STATUS** section), it asks for more input; otherwise, it exits with the
964 appropriate return code.
968 Most dc(1) implementations use **char** types to calculate the value of **1**
969 decimal digit at a time, but that can be slow. This dc(1) does something
972 It uses large integers to calculate more than **1** decimal digit at a time. If
973 built in a environment where **DC_LONG_BIT** (see the **LIMITS** section) is
974 **64**, then each integer has **9** decimal digits. If built in an environment
975 where **DC_LONG_BIT** is **32** then each integer has **4** decimal digits. This
976 value (the number of decimal digits per large integer) is called
979 In addition, this dc(1) uses an even larger integer for overflow checking. This
980 integer type depends on the value of **DC_LONG_BIT**, but is always at least
981 twice as large as the integer type used to store digits.
985 The following are the limits on dc(1):
989 : The number of bits in the **long** type in the environment where dc(1) was
990 built. This determines how many decimal digits can be stored in a single
991 large integer (see the **PERFORMANCE** section).
995 : The number of decimal digits per large integer (see the **PERFORMANCE**
996 section). Depends on **DC_LONG_BIT**.
1000 : The max decimal number that each large integer can store (see
1001 **DC_BASE_DIGS**) plus **1**. Depends on **DC_BASE_DIGS**.
1005 : The max number that the overflow type (see the **PERFORMANCE** section) can
1006 hold. Depends on **DC_LONG_BIT**.
1010 : The maximum output base. Set at **DC_BASE_POW**.
1014 : The maximum size of arrays. Set at **SIZE_MAX-1**.
1018 : The maximum **scale**. Set at **DC_OVERFLOW_MAX-1**.
1022 : The maximum length of strings. Set at **DC_OVERFLOW_MAX-1**.
1026 : The maximum length of identifiers. Set at **DC_OVERFLOW_MAX-1**.
1030 : The maximum length of a number (in decimal digits), which includes digits
1031 after the decimal point. Set at **DC_OVERFLOW_MAX-1**.
1033 {{ A H N P HN HP NP HNP }}
1036 : The maximum integer (inclusive) returned by the **'** command, if dc(1). Set
1037 at **2\^DC_LONG_BIT-1**.
1042 : The maximum allowable exponent (positive or negative). Set at
1043 **DC_OVERFLOW_MAX**.
1047 : The maximum number of vars/arrays. Set at **SIZE_MAX-1**.
1049 These limits are meant to be effectively non-existent; the limits are so large
1050 (at least on 64-bit machines) that there should not be any point at which they
1051 become a problem. In fact, memory should be exhausted before these limits should
1054 # ENVIRONMENT VARIABLES
1056 dc(1) recognizes the following environment variables:
1060 : This is another way to give command-line arguments to dc(1). They should be
1061 in the same format as all other command-line arguments. These are always
1062 processed first, so any files given in **DC_ENV_ARGS** will be processed
1063 before arguments and files given on the command-line. This gives the user
1064 the ability to set up "standard" options and files to be used at every
1065 invocation. The most useful thing for such files to contain would be useful
1066 functions that the user might want every time dc(1) runs. Another use would
1067 be to use the **-e** option to set **scale** to a value other than **0**.
1069 The code that parses **DC_ENV_ARGS** will correctly handle quoted arguments,
1070 but it does not understand escape sequences. For example, the string
1071 **"/home/gavin/some dc file.dc"** will be correctly parsed, but the string
1072 **"/home/gavin/some \"dc\" file.dc"** will include the backslashes.
1074 The quote parsing will handle either kind of quotes, **'** or **"**. Thus,
1075 if you have a file with any number of single quotes in the name, you can use
1076 double quotes as the outside quotes, as in **"some 'bc' file.bc"**, and vice
1077 versa if you have a file with double quotes. However, handling a file with
1078 both kinds of quotes in **DC_ENV_ARGS** is not supported due to the
1079 complexity of the parsing, though such files are still supported on the
1080 command-line where the parsing is done by the shell.
1084 : If this environment variable exists and contains an integer that is greater
1085 than **1** and is less than **UINT16_MAX** (**2\^16-1**), dc(1) will output
1086 lines to that length, including the backslash newline combo. The default
1087 line length is **70**.
1091 : If this variable exists (no matter the contents), dc(1) will exit
1092 immediately after executing expressions and files given by the **-e** and/or
1093 **-f** command-line options (and any equivalents).
1097 dc(1) returns the following exit statuses:
1105 : A math error occurred. This follows standard practice of using **1** for
1106 expected errors, since math errors will happen in the process of normal
1109 Math errors include divide by **0**, taking the square root of a negative
1110 {{ A H N P HN HP NP HNP }}
1111 number, using a negative number as a bound for the pseudo-random number
1112 generator, attempting to convert a negative number to a hardware integer,
1113 overflow when converting a number to a hardware integer, and attempting to
1114 use a non-integer where an integer is required.
1116 Converting to a hardware integer happens for the second operand of the power
1117 (**\^**), places (**\@**), left shift (**H**), and right shift (**h**)
1120 {{ E EH EN EP EHN EHP ENP EHNP }}
1121 number, attempting to convert a negative number to a hardware integer,
1122 overflow when converting a number to a hardware integer, and attempting to
1123 use a non-integer where an integer is required.
1125 Converting to a hardware integer happens for the second operand of the power
1131 : A parse error occurred.
1133 Parse errors include unexpected **EOF**, using an invalid character, failing
1134 to find the end of a string or comment, and using a token where it is
1139 : A runtime error occurred.
1141 Runtime errors include assigning an invalid number to **ibase**, **obase**,
1142 or **scale**; give a bad expression to a **read()** call, calling **read()**
1143 inside of a **read()** call, type errors, and attempting an operation when
1144 the stack has too few elements.
1148 : A fatal error occurred.
1150 Fatal errors include memory allocation errors, I/O errors, failing to open
1151 files, attempting to use files that do not have only ASCII characters (dc(1)
1152 only accepts ASCII characters), attempting to open a directory as a file,
1153 and giving invalid command-line options.
1155 The exit status **4** is special; when a fatal error occurs, dc(1) always exits
1156 and returns **4**, no matter what mode dc(1) is in.
1158 The other statuses will only be returned when dc(1) is not in interactive mode
1159 (see the **INTERACTIVE MODE** section), since dc(1) resets its state (see the
1160 **RESET** section) and accepts more input when one of those errors occurs in
1161 interactive mode. This is also the case when interactive mode is forced by the
1162 **-i** flag or **--interactive** option.
1164 These exit statuses allow dc(1) to be used in shell scripting with error
1165 checking, and its normal behavior can be forced by using the **-i** flag or
1166 **--interactive** option.
1170 Like bc(1), dc(1) has an interactive mode and a non-interactive mode.
1171 Interactive mode is turned on automatically when both **stdin** and **stdout**
1172 are hooked to a terminal, but the **-i** flag and **--interactive** option can
1173 turn it on in other cases.
1175 In interactive mode, dc(1) attempts to recover from errors (see the **RESET**
1176 section), and in normal execution, flushes **stdout** as soon as execution is
1177 done for the current input.
1181 If **stdin**, **stdout**, and **stderr** are all connected to a TTY, dc(1) turns
1184 {{ A E N P EN EP NP ENP }}
1185 TTY mode is required for history to be enabled (see the **COMMAND LINE HISTORY**
1186 section). It is also required to enable special handling for **SIGINT** signals.
1189 {{ A E H N EH EN HN EHN }}
1190 The prompt is enabled in TTY mode.
1193 TTY mode is different from interactive mode because interactive mode is required
1194 in the [bc(1) specification][1], and interactive mode requires only **stdin**
1195 and **stdout** to be connected to a terminal.
1199 Sending a **SIGINT** will cause dc(1) to stop execution of the current input. If
1200 dc(1) is in TTY mode (see the **TTY MODE** section), it will reset (see the
1201 **RESET** section). Otherwise, it will clean up and exit.
1203 Note that "current input" can mean one of two things. If dc(1) is processing
1204 input from **stdin** in TTY mode, it will ask for more input. If dc(1) is
1205 processing input from a file in TTY mode, it will stop processing the file and
1206 start processing the next file, if one exists, or ask for input from **stdin**
1207 if no other file exists.
1209 This means that if a **SIGINT** is sent to dc(1) as it is executing a file, it
1210 can seem as though dc(1) did not respond to the signal since it will immediately
1211 start executing the next file. This is by design; most files that users execute
1212 when interacting with dc(1) have function definitions, which are quick to parse.
1213 If a file takes a long time to execute, there may be a bug in that file. The
1214 rest of the files could still be executed without problem, allowing the user to
1217 **SIGTERM** and **SIGQUIT** cause dc(1) to clean up and exit, and it uses the
1218 {{ A E N P EN EP NP ENP }}
1219 default handler for all other signals. The one exception is **SIGHUP**; in that
1220 case, when dc(1) is in TTY mode, a **SIGHUP** will cause dc(1) to clean up and
1223 {{ H EH HN HP EHN EHP HNP EHNP }}
1224 default handler for all other signals.
1227 {{ A E N P EN EP NP ENP }}
1228 # COMMAND LINE HISTORY
1230 dc(1) supports interactive command-line editing. If dc(1) is in TTY mode (see
1231 the **TTY MODE** section), history is enabled. Previous lines can be recalled
1232 and edited with the arrow keys.
1234 **Note**: tabs are converted to 8 spaces.
1237 {{ A E H P EH EP HP EHP }}
1240 This dc(1) ships with support for adding error messages for different locales
1241 and thus, supports **LC_MESSAGS**.
1250 The dc(1) utility operators are compliant with the operators in the bc(1)
1251 [IEEE Std 1003.1-2017 (“POSIX.1-2017”)][1] specification.
1255 None are known. Report bugs at https://git.yzena.com/gavin/bc.
1259 Gavin D. Howard <gavin@yzena.com> and contributors.
1261 [1]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html