1<!--- 2 3SPDX-License-Identifier: BSD-2-Clause 4 5Copyright (c) 2018-2021 Gavin D. Howard and contributors. 6 7Redistribution and use in source and binary forms, with or without 8modification, are permitted provided that the following conditions are met: 9 10* Redistributions of source code must retain the above copyright notice, this 11 list of conditions and the following disclaimer. 12 13* Redistributions in binary form must reproduce the above copyright notice, 14 this list of conditions and the following disclaimer in the documentation 15 and/or other materials provided with the distribution. 16 17THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 18AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 21LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 22CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 23SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 25CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 26ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 27POSSIBILITY OF SUCH DAMAGE. 28 29--> 30 31# Name 32 33dc - arbitrary-precision decimal reverse-Polish notation calculator 34 35# SYNOPSIS 36 37**dc** [**-hiPRvVx**] [**-\-version**] [**-\-help**] [**-\-interactive**] [**-\-no-prompt**] [**-\-no-read-prompt**] [**-\-extended-register**] [**-e** *expr*] [**-\-expression**=*expr*...] [**-f** *file*...] [**-\-file**=*file*...] [*file*...] 38 39# DESCRIPTION 40 41dc(1) is an arbitrary-precision calculator. It uses a stack (reverse Polish 42notation) to store numbers and results of computations. Arithmetic operations 43pop arguments off of the stack and push the results. 44 45If no files are given on the command-line, then dc(1) reads from **stdin** (see 46the **STDIN** section). Otherwise, those files are processed, and dc(1) will 47then exit. 48 49If a user wants to set up a standard environment, they can use **DC_ENV_ARGS** 50(see the **ENVIRONMENT VARIABLES** section). For example, if a user wants the 51**scale** always set to **10**, they can set **DC_ENV_ARGS** to **-e 10k**, and 52this dc(1) will always start with a **scale** of **10**. 53 54# OPTIONS 55 56The following are the options that dc(1) accepts. 57 58**-h**, **-\-help** 59 60: Prints a usage message and quits. 61 62**-v**, **-V**, **-\-version** 63 64: Print the version information (copyright header) and exit. 65 66**-i**, **-\-interactive** 67 68: Forces interactive mode. (See the **INTERACTIVE MODE** section.) 69 70 This is a **non-portable extension**. 71 72**-L**, **-\-no-line-length** 73 74: Disables line length checking and prints numbers without backslashes and 75 newlines. In other words, this option sets **BC_LINE_LENGTH** to **0** (see 76 the **ENVIRONMENT VARIABLES** section). 77 78 This is a **non-portable extension**. 79 80**-P**, **-\-no-prompt** 81 82: Disables the prompt in TTY mode. (The prompt is only enabled in TTY mode. 83 See the **TTY MODE** section.) This is mostly for those users that do not 84 want a prompt or are not used to having them in dc(1). Most of those users 85 would want to put this option in **DC_ENV_ARGS**. 86 87 These options override the **DC_PROMPT** and **DC_TTY_MODE** environment 88 variables (see the **ENVIRONMENT VARIABLES** section). 89 90 This is a **non-portable extension**. 91 92**-R**, **-\-no-read-prompt** 93 94: Disables the read prompt in TTY mode. (The read prompt is only enabled in 95 TTY mode. See the **TTY MODE** section.) This is mostly for those users that 96 do not want a read prompt or are not used to having them in dc(1). Most of 97 those users would want to put this option in **BC_ENV_ARGS** (see the 98 **ENVIRONMENT VARIABLES** section). This option is also useful in hash bang 99 lines of dc(1) scripts that prompt for user input. 100 101 This option does not disable the regular prompt because the read prompt is 102 only used when the **?** command is used. 103 104 These options *do* override the **DC_PROMPT** and **DC_TTY_MODE** 105 environment variables (see the **ENVIRONMENT VARIABLES** section), but only 106 for the read prompt. 107 108 This is a **non-portable extension**. 109 110**-x** **-\-extended-register** 111 112: Enables extended register mode. See the *Extended Register Mode* subsection 113 of the **REGISTERS** section for more information. 114 115 This is a **non-portable extension**. 116 117**-z**, **-\-leading-zeroes** 118 119: Makes bc(1) print all numbers greater than **-1** and less than **1**, and 120 not equal to **0**, with a leading zero. 121 122 This can be set for individual numbers with the **plz(x)**, plznl(x)**, 123 **pnlz(x)**, and **pnlznl(x)** functions in the extended math library (see 124 the **LIBRARY** section). 125 126 This is a **non-portable extension**. 127 128**-e** *expr*, **-\-expression**=*expr* 129 130: Evaluates *expr*. If multiple expressions are given, they are evaluated in 131 order. If files are given as well (see below), the expressions and files are 132 evaluated in the order given. This means that if a file is given before an 133 expression, the file is read in and evaluated first. 134 135 If this option is given on the command-line (i.e., not in **DC_ENV_ARGS**, 136 see the **ENVIRONMENT VARIABLES** section), then after processing all 137 expressions and files, dc(1) will exit, unless **-** (**stdin**) was given 138 as an argument at least once to **-f** or **-\-file**, whether on the 139 command-line or in **DC_ENV_ARGS**. However, if any other **-e**, 140 **-\-expression**, **-f**, or **-\-file** arguments are given after **-f-** 141 or equivalent is given, dc(1) will give a fatal error and exit. 142 143 This is a **non-portable extension**. 144 145**-f** *file*, **-\-file**=*file* 146 147: Reads in *file* and evaluates it, line by line, as though it were read 148 through **stdin**. If expressions are also given (see above), the 149 expressions are evaluated in the order given. 150 151 If this option is given on the command-line (i.e., not in **DC_ENV_ARGS**, 152 see the **ENVIRONMENT VARIABLES** section), then after processing all 153 expressions and files, dc(1) will exit, unless **-** (**stdin**) was given 154 as an argument at least once to **-f** or **-\-file**. However, if any other 155 **-e**, **-\-expression**, **-f**, or **-\-file** arguments are given after 156 **-f-** or equivalent is given, dc(1) will give a fatal error and exit. 157 158 This is a **non-portable extension**. 159 160All long options are **non-portable extensions**. 161 162# STDIN 163 164If no files are given on the command-line and no files or expressions are given 165by the **-f**, **-\-file**, **-e**, or **-\-expression** options, then dc(1) 166read from **stdin**. 167 168However, there is a caveat to this. 169 170First, **stdin** is evaluated a line at a time. The only exception to this is if 171a string has been finished, but not ended. This means that, except for escaped 172brackets, all brackets must be balanced before dc(1) parses and executes. 173 174# STDOUT 175 176Any non-error output is written to **stdout**. In addition, if history (see the 177**HISTORY** section) and the prompt (see the **TTY MODE** section) are enabled, 178both are output to **stdout**. 179 180**Note**: Unlike other dc(1) implementations, this dc(1) will issue a fatal 181error (see the **EXIT STATUS** section) if it cannot write to **stdout**, so if 182**stdout** is closed, as in **dc <file> >&-**, it will quit with an error. This 183is done so that dc(1) can report problems when **stdout** is redirected to a 184file. 185 186If there are scripts that depend on the behavior of other dc(1) implementations, 187it is recommended that those scripts be changed to redirect **stdout** to 188**/dev/null**. 189 190# STDERR 191 192Any error output is written to **stderr**. 193 194**Note**: Unlike other dc(1) implementations, this dc(1) will issue a fatal 195error (see the **EXIT STATUS** section) if it cannot write to **stderr**, so if 196**stderr** is closed, as in **dc <file> 2>&-**, it will quit with an error. This 197is done so that dc(1) can exit with an error code when **stderr** is redirected 198to a file. 199 200If there are scripts that depend on the behavior of other dc(1) implementations, 201it is recommended that those scripts be changed to redirect **stderr** to 202**/dev/null**. 203 204# SYNTAX 205 206Each item in the input source code, either a number (see the **NUMBERS** 207section) or a command (see the **COMMANDS** section), is processed and executed, 208in order. Input is processed immediately when entered. 209 210**ibase** is a register (see the **REGISTERS** section) that determines how to 211interpret constant numbers. It is the "input" base, or the number base used for 212interpreting input numbers. **ibase** is initially **10**. The max allowable 213value for **ibase** is **16**. The min allowable value for **ibase** is **2**. 214The max allowable value for **ibase** can be queried in dc(1) programs with the 215**T** command. 216 217**obase** is a register (see the **REGISTERS** section) that determines how to 218output results. It is the "output" base, or the number base used for outputting 219numbers. **obase** is initially **10**. The max allowable value for **obase** is 220**DC_BASE_MAX** and can be queried with the **U** command. The min allowable 221value for **obase** is **0**. If **obase** is **0**, values are output in 222scientific notation, and if **obase** is **1**, values are output in engineering 223notation. Otherwise, values are output in the specified base. 224 225Outputting in scientific and engineering notations are **non-portable 226extensions**. 227 228The *scale* of an expression is the number of digits in the result of the 229expression right of the decimal point, and **scale** is a register (see the 230**REGISTERS** section) that sets the precision of any operations (with 231exceptions). **scale** is initially **0**. **scale** cannot be negative. The max 232allowable value for **scale** can be queried in dc(1) programs with the **V** 233command. 234 235**seed** is a register containing the current seed for the pseudo-random number 236generator. If the current value of **seed** is queried and stored, then if it is 237assigned to **seed** later, the pseudo-random number generator is guaranteed to 238produce the same sequence of pseudo-random numbers that were generated after the 239value of **seed** was first queried. 240 241Multiple values assigned to **seed** can produce the same sequence of 242pseudo-random numbers. Likewise, when a value is assigned to **seed**, it is not 243guaranteed that querying **seed** immediately after will return the same value. 244In addition, the value of **seed** will change after any call to the **'** 245command or the **"** command that does not get receive a value of **0** or 246**1**. The maximum integer returned by the **'** command can be queried with the 247**W** command. 248 249**Note**: The values returned by the pseudo-random number generator with the 250**'** and **"** commands are guaranteed to **NOT** be cryptographically secure. 251This is a consequence of using a seeded pseudo-random number generator. However, 252they *are* guaranteed to be reproducible with identical **seed** values. This 253means that the pseudo-random values from dc(1) should only be used where a 254reproducible stream of pseudo-random numbers is *ESSENTIAL*. In any other case, 255use a non-seeded pseudo-random number generator. 256 257The pseudo-random number generator, **seed**, and all associated operations are 258**non-portable extensions**. 259 260## Comments 261 262Comments go from **#** until, and not including, the next newline. This is a 263**non-portable extension**. 264 265# NUMBERS 266 267Numbers are strings made up of digits, uppercase letters up to **F**, and at 268most **1** period for a radix. Numbers can have up to **DC_NUM_MAX** digits. 269Uppercase letters are equal to **9** + their position in the alphabet (i.e., 270**A** equals **10**, or **9+1**). If a digit or letter makes no sense with the 271current value of **ibase**, they are set to the value of the highest valid digit 272in **ibase**. 273 274Single-character numbers (i.e., **A** alone) take the value that they would have 275if they were valid digits, regardless of the value of **ibase**. This means that 276**A** alone always equals decimal **10** and **F** alone always equals decimal 277**15**. 278 279In addition, dc(1) accepts numbers in scientific notation. These have the form 280**\<number\>e\<integer\>**. The exponent (the portion after the **e**) must be 281an integer. An example is **1.89237e9**, which is equal to **1892370000**. 282Negative exponents are also allowed, so **4.2890e_3** is equal to **0.0042890**. 283 284**WARNING**: Both the number and the exponent in scientific notation are 285interpreted according to the current **ibase**, but the number is still 286multiplied by **10\^exponent** regardless of the current **ibase**. For example, 287if **ibase** is **16** and dc(1) is given the number string **FFeA**, the 288resulting decimal number will be **2550000000000**, and if dc(1) is given the 289number string **10e_4**, the resulting decimal number will be **0.0016**. 290 291Accepting input as scientific notation is a **non-portable extension**. 292 293# COMMANDS 294 295The valid commands are listed below. 296 297## Printing 298 299These commands are used for printing. 300 301Note that both scientific notation and engineering notation are available for 302printing numbers. Scientific notation is activated by assigning **0** to 303**obase** using **0o**, and engineering notation is activated by assigning **1** 304to **obase** using **1o**. To deactivate them, just assign a different value to 305**obase**. 306 307Printing numbers in scientific notation and/or engineering notation is a 308**non-portable extension**. 309 310**p** 311 312: Prints the value on top of the stack, whether number or string, and prints a 313 newline after. 314 315 This does not alter the stack. 316 317**n** 318 319: Prints the value on top of the stack, whether number or string, and pops it 320 off of the stack. 321 322**P** 323 324: Pops a value off the stack. 325 326 If the value is a number, it is truncated and the absolute value of the 327 result is printed as though **obase** is **256** and each digit is 328 interpreted as an 8-bit ASCII character, making it a byte stream. 329 330 If the value is a string, it is printed without a trailing newline. 331 332 This is a **non-portable extension**. 333 334**f** 335 336: Prints the entire contents of the stack, in order from newest to oldest, 337 without altering anything. 338 339 Users should use this command when they get lost. 340 341## Arithmetic 342 343These are the commands used for arithmetic. 344 345**+** 346 347: The top two values are popped off the stack, added, and the result is pushed 348 onto the stack. The *scale* of the result is equal to the max *scale* of 349 both operands. 350 351**-** 352 353: The top two values are popped off the stack, subtracted, and the result is 354 pushed onto the stack. The *scale* of the result is equal to the max 355 *scale* of both operands. 356 357**\*** 358 359: The top two values are popped off the stack, multiplied, and the result is 360 pushed onto the stack. If **a** is the *scale* of the first expression and 361 **b** is the *scale* of the second expression, the *scale* of the result 362 is equal to **min(a+b,max(scale,a,b))** where **min()** and **max()** return 363 the obvious values. 364 365**/** 366 367: The top two values are popped off the stack, divided, and the result is 368 pushed onto the stack. The *scale* of the result is equal to **scale**. 369 370 The first value popped off of the stack must be non-zero. 371 372**%** 373 374: The top two values are popped off the stack, remaindered, and the result is 375 pushed onto the stack. 376 377 Remaindering is equivalent to 1) Computing **a/b** to current **scale**, and 378 2) Using the result of step 1 to calculate **a-(a/b)\*b** to *scale* 379 **max(scale+scale(b),scale(a))**. 380 381 The first value popped off of the stack must be non-zero. 382 383**~** 384 385: The top two values are popped off the stack, divided and remaindered, and 386 the results (divided first, remainder second) are pushed onto the stack. 387 This is equivalent to **x y / x y %** except that **x** and **y** are only 388 evaluated once. 389 390 The first value popped off of the stack must be non-zero. 391 392 This is a **non-portable extension**. 393 394**\^** 395 396: The top two values are popped off the stack, the second is raised to the 397 power of the first, and the result is pushed onto the stack. The *scale* of 398 the result is equal to **scale**. 399 400 The first value popped off of the stack must be an integer, and if that 401 value is negative, the second value popped off of the stack must be 402 non-zero. 403 404**v** 405 406: The top value is popped off the stack, its square root is computed, and the 407 result is pushed onto the stack. The *scale* of the result is equal to 408 **scale**. 409 410 The value popped off of the stack must be non-negative. 411 412**\_** 413 414: If this command *immediately* precedes a number (i.e., no spaces or other 415 commands), then that number is input as a negative number. 416 417 Otherwise, the top value on the stack is popped and copied, and the copy is 418 negated and pushed onto the stack. This behavior without a number is a 419 **non-portable extension**. 420 421**b** 422 423: The top value is popped off the stack, and if it is zero, it is pushed back 424 onto the stack. Otherwise, its absolute value is pushed onto the stack. 425 426 This is a **non-portable extension**. 427 428**|** 429 430: The top three values are popped off the stack, a modular exponentiation is 431 computed, and the result is pushed onto the stack. 432 433 The first value popped is used as the reduction modulus and must be an 434 integer and non-zero. The second value popped is used as the exponent and 435 must be an integer and non-negative. The third value popped is the base and 436 must be an integer. 437 438 This is a **non-portable extension**. 439 440**\$** 441 442: The top value is popped off the stack and copied, and the copy is truncated 443 and pushed onto the stack. 444 445 This is a **non-portable extension**. 446 447**\@** 448 449: The top two values are popped off the stack, and the precision of the second 450 is set to the value of the first, whether by truncation or extension. 451 452 The first value popped off of the stack must be an integer and non-negative. 453 454 This is a **non-portable extension**. 455 456**H** 457 458: The top two values are popped off the stack, and the second is shifted left 459 (radix shifted right) to the value of the first. 460 461 The first value popped off of the stack must be an integer and non-negative. 462 463 This is a **non-portable extension**. 464 465**h** 466 467: The top two values are popped off the stack, and the second is shifted right 468 (radix shifted left) to the value of the first. 469 470 The first value popped off of the stack must be an integer and non-negative. 471 472 This is a **non-portable extension**. 473 474**G** 475 476: The top two values are popped off of the stack, they are compared, and a 477 **1** is pushed if they are equal, or **0** otherwise. 478 479 This is a **non-portable extension**. 480 481**N** 482 483: The top value is popped off of the stack, and if it a **0**, a **1** is 484 pushed; otherwise, a **0** is pushed. 485 486 This is a **non-portable extension**. 487 488**(** 489 490: The top two values are popped off of the stack, they are compared, and a 491 **1** is pushed if the first is less than the second, or **0** otherwise. 492 493 This is a **non-portable extension**. 494 495**{** 496 497: The top two values are popped off of the stack, they are compared, and a 498 **1** is pushed if the first is less than or equal to the second, or **0** 499 otherwise. 500 501 This is a **non-portable extension**. 502 503**)** 504 505: The top two values are popped off of the stack, they are compared, and a 506 **1** is pushed if the first is greater than the second, or **0** otherwise. 507 508 This is a **non-portable extension**. 509 510**}** 511 512: The top two values are popped off of the stack, they are compared, and a 513 **1** is pushed if the first is greater than or equal to the second, or 514 **0** otherwise. 515 516 This is a **non-portable extension**. 517 518**M** 519 520: The top two values are popped off of the stack. If they are both non-zero, a 521 **1** is pushed onto the stack. If either of them is zero, or both of them 522 are, then a **0** is pushed onto the stack. 523 524 This is like the **&&** operator in bc(1), and it is *not* a short-circuit 525 operator. 526 527 This is a **non-portable extension**. 528 529**m** 530 531: The top two values are popped off of the stack. If at least one of them is 532 non-zero, a **1** is pushed onto the stack. If both of them are zero, then a 533 **0** is pushed onto the stack. 534 535 This is like the **||** operator in bc(1), and it is *not* a short-circuit 536 operator. 537 538 This is a **non-portable extension**. 539 540## Pseudo-Random Number Generator 541 542dc(1) has a built-in pseudo-random number generator. These commands query the 543pseudo-random number generator. (See Parameters for more information about the 544**seed** value that controls the pseudo-random number generator.) 545 546The pseudo-random number generator is guaranteed to **NOT** be 547cryptographically secure. 548 549**'** 550 551: Generates an integer between 0 and **DC_RAND_MAX**, inclusive (see the 552 **LIMITS** section). 553 554 The generated integer is made as unbiased as possible, subject to the 555 limitations of the pseudo-random number generator. 556 557 This is a **non-portable extension**. 558 559**"** 560 561: Pops a value off of the stack, which is used as an **exclusive** upper bound 562 on the integer that will be generated. If the bound is negative or is a 563 non-integer, an error is raised, and dc(1) resets (see the **RESET** 564 section) while **seed** remains unchanged. If the bound is larger than 565 **DC_RAND_MAX**, the higher bound is honored by generating several 566 pseudo-random integers, multiplying them by appropriate powers of 567 **DC_RAND_MAX+1**, and adding them together. Thus, the size of integer that 568 can be generated with this command is unbounded. Using this command will 569 change the value of **seed**, unless the operand is **0** or **1**. In that 570 case, **0** is pushed onto the stack, and **seed** is *not* changed. 571 572 The generated integer is made as unbiased as possible, subject to the 573 limitations of the pseudo-random number generator. 574 575 This is a **non-portable extension**. 576 577## Stack Control 578 579These commands control the stack. 580 581**c** 582 583: Removes all items from ("clears") the stack. 584 585**d** 586 587: Copies the item on top of the stack ("duplicates") and pushes the copy onto 588 the stack. 589 590**r** 591 592: Swaps ("reverses") the two top items on the stack. 593 594**R** 595 596: Pops ("removes") the top value from the stack. 597 598## Register Control 599 600These commands control registers (see the **REGISTERS** section). 601 602**s**_r_ 603 604: Pops the value off the top of the stack and stores it into register *r*. 605 606**l**_r_ 607 608: Copies the value in register *r* and pushes it onto the stack. This does not 609 alter the contents of *r*. 610 611**S**_r_ 612 613: Pops the value off the top of the (main) stack and pushes it onto the stack 614 of register *r*. The previous value of the register becomes inaccessible. 615 616**L**_r_ 617 618: Pops the value off the top of the stack for register *r* and push it onto 619 the main stack. The previous value in the stack for register *r*, if any, is 620 now accessible via the **l**_r_ command. 621 622## Parameters 623 624These commands control the values of **ibase**, **obase**, **scale**, and 625**seed**. Also see the **SYNTAX** section. 626 627**i** 628 629: Pops the value off of the top of the stack and uses it to set **ibase**, 630 which must be between **2** and **16**, inclusive. 631 632 If the value on top of the stack has any *scale*, the *scale* is ignored. 633 634**o** 635 636: Pops the value off of the top of the stack and uses it to set **obase**, 637 which must be between **0** and **DC_BASE_MAX**, inclusive (see the 638 **LIMITS** section and the **NUMBERS** section). 639 640 If the value on top of the stack has any *scale*, the *scale* is ignored. 641 642**k** 643 644: Pops the value off of the top of the stack and uses it to set **scale**, 645 which must be non-negative. 646 647 If the value on top of the stack has any *scale*, the *scale* is ignored. 648 649**j** 650 651: Pops the value off of the top of the stack and uses it to set **seed**. The 652 meaning of **seed** is dependent on the current pseudo-random number 653 generator but is guaranteed to not change except for new major versions. 654 655 The *scale* and sign of the value may be significant. 656 657 If a previously used **seed** value is used again, the pseudo-random number 658 generator is guaranteed to produce the same sequence of pseudo-random 659 numbers as it did when the **seed** value was previously used. 660 661 The exact value assigned to **seed** is not guaranteed to be returned if the 662 **J** command is used. However, if **seed** *does* return a different value, 663 both values, when assigned to **seed**, are guaranteed to produce the same 664 sequence of pseudo-random numbers. This means that certain values assigned 665 to **seed** will not produce unique sequences of pseudo-random numbers. 666 667 There is no limit to the length (number of significant decimal digits) or 668 *scale* of the value that can be assigned to **seed**. 669 670 This is a **non-portable extension**. 671 672**I** 673 674: Pushes the current value of **ibase** onto the main stack. 675 676**O** 677 678: Pushes the current value of **obase** onto the main stack. 679 680**K** 681 682: Pushes the current value of **scale** onto the main stack. 683 684**J** 685 686: Pushes the current value of **seed** onto the main stack. 687 688 This is a **non-portable extension**. 689 690**T** 691 692: Pushes the maximum allowable value of **ibase** onto the main stack. 693 694 This is a **non-portable extension**. 695 696**U** 697 698: Pushes the maximum allowable value of **obase** onto the main stack. 699 700 This is a **non-portable extension**. 701 702**V** 703 704: Pushes the maximum allowable value of **scale** onto the main stack. 705 706 This is a **non-portable extension**. 707 708**W** 709 710: Pushes the maximum (inclusive) integer that can be generated with the **'** 711 pseudo-random number generator command. 712 713 This is a **non-portable extension**. 714 715## Strings 716 717The following commands control strings. 718 719dc(1) can work with both numbers and strings, and registers (see the 720**REGISTERS** section) can hold both strings and numbers. dc(1) always knows 721whether the contents of a register are a string or a number. 722 723While arithmetic operations have to have numbers, and will print an error if 724given a string, other commands accept strings. 725 726Strings can also be executed as macros. For example, if the string **[1pR]** is 727executed as a macro, then the code **1pR** is executed, meaning that the **1** 728will be printed with a newline after and then popped from the stack. 729 730**\[**_characters_**\]** 731 732: Makes a string containing *characters* and pushes it onto the stack. 733 734 If there are brackets (**\[** and **\]**) in the string, then they must be 735 balanced. Unbalanced brackets can be escaped using a backslash (**\\**) 736 character. 737 738 If there is a backslash character in the string, the character after it 739 (even another backslash) is put into the string verbatim, but the (first) 740 backslash is not. 741 742**a** 743 744: The value on top of the stack is popped. 745 746 If it is a number, it is truncated and its absolute value is taken. The 747 result mod **256** is calculated. If that result is **0**, push an empty 748 string; otherwise, push a one-character string where the character is the 749 result of the mod interpreted as an ASCII character. 750 751 If it is a string, then a new string is made. If the original string is 752 empty, the new string is empty. If it is not, then the first character of 753 the original string is used to create the new string as a one-character 754 string. The new string is then pushed onto the stack. 755 756 This is a **non-portable extension**. 757 758**x** 759 760: Pops a value off of the top of the stack. 761 762 If it is a number, it is pushed back onto the stack. 763 764 If it is a string, it is executed as a macro. 765 766 This behavior is the norm whenever a macro is executed, whether by this 767 command or by the conditional execution commands below. 768 769**\>**_r_ 770 771: Pops two values off of the stack that must be numbers and compares them. If 772 the first value is greater than the second, then the contents of register 773 *r* are executed. 774 775 For example, **0 1>a** will execute the contents of register **a**, and 776 **1 0>a** will not. 777 778 If either or both of the values are not numbers, dc(1) will raise an error 779 and reset (see the **RESET** section). 780 781**>**_r_**e**_s_ 782 783: Like the above, but will execute register *s* if the comparison fails. 784 785 If either or both of the values are not numbers, dc(1) will raise an error 786 and reset (see the **RESET** section). 787 788 This is a **non-portable extension**. 789 790**!\>**_r_ 791 792: Pops two values off of the stack that must be numbers and compares them. If 793 the first value is not greater than the second (less than or equal to), then 794 the contents of register *r* are executed. 795 796 If either or both of the values are not numbers, dc(1) will raise an error 797 and reset (see the **RESET** section). 798 799**!\>**_r_**e**_s_ 800 801: Like the above, but will execute register *s* if the comparison fails. 802 803 If either or both of the values are not numbers, dc(1) will raise an error 804 and reset (see the **RESET** section). 805 806 This is a **non-portable extension**. 807 808**\<**_r_ 809 810: Pops two values off of the stack that must be numbers and compares them. If 811 the first value is less than the second, then the contents of register *r* 812 are executed. 813 814 If either or both of the values are not numbers, dc(1) will raise an error 815 and reset (see the **RESET** section). 816 817**\<**_r_**e**_s_ 818 819: Like the above, but will execute register *s* if the comparison fails. 820 821 If either or both of the values are not numbers, dc(1) will raise an error 822 and reset (see the **RESET** section). 823 824 This is a **non-portable extension**. 825 826**!\<**_r_ 827 828: Pops two values off of the stack that must be numbers and compares them. If 829 the first value is not less than the second (greater than or equal to), then 830 the contents of register *r* are executed. 831 832 If either or both of the values are not numbers, dc(1) will raise an error 833 and reset (see the **RESET** section). 834 835**!\<**_r_**e**_s_ 836 837: Like the above, but will execute register *s* if the comparison fails. 838 839 If either or both of the values are not numbers, dc(1) will raise an error 840 and reset (see the **RESET** section). 841 842 This is a **non-portable extension**. 843 844**=**_r_ 845 846: Pops two values off of the stack that must be numbers and compares them. If 847 the first value is equal to the second, then the contents of register *r* 848 are executed. 849 850 If either or both of the values are not numbers, dc(1) will raise an error 851 and reset (see the **RESET** section). 852 853**=**_r_**e**_s_ 854 855: Like the above, but will execute register *s* if the comparison fails. 856 857 If either or both of the values are not numbers, dc(1) will raise an error 858 and reset (see the **RESET** section). 859 860 This is a **non-portable extension**. 861 862**!=**_r_ 863 864: Pops two values off of the stack that must be numbers and compares them. If 865 the first value is not equal to the second, then the contents of register 866 *r* are executed. 867 868 If either or both of the values are not numbers, dc(1) will raise an error 869 and reset (see the **RESET** section). 870 871**!=**_r_**e**_s_ 872 873: Like the above, but will execute register *s* if the comparison fails. 874 875 If either or both of the values are not numbers, dc(1) will raise an error 876 and reset (see the **RESET** section). 877 878 This is a **non-portable extension**. 879 880**?** 881 882: Reads a line from the **stdin** and executes it. This is to allow macros to 883 request input from users. 884 885**q** 886 887: During execution of a macro, this exits the execution of that macro and the 888 execution of the macro that executed it. If there are no macros, or only one 889 macro executing, dc(1) exits. 890 891**Q** 892 893: Pops a value from the stack which must be non-negative and is used the 894 number of macro executions to pop off of the execution stack. If the number 895 of levels to pop is greater than the number of executing macros, dc(1) 896 exits. 897 898**,** 899 900: Pushes the depth of the execution stack onto the stack. The execution stack 901 is the stack of string executions. The number that is pushed onto the stack 902 is exactly as many as is needed to make dc(1) exit with the **Q** command, 903 so the sequence **,Q** will make dc(1) exit. 904 905## Status 906 907These commands query status of the stack or its top value. 908 909**Z** 910 911: Pops a value off of the stack. 912 913 If it is a number, calculates the number of significant decimal digits it 914 has and pushes the result. It will push **1** if the argument is **0** with 915 no decimal places. 916 917 If it is a string, pushes the number of characters the string has. 918 919**X** 920 921: Pops a value off of the stack. 922 923 If it is a number, pushes the *scale* of the value onto the stack. 924 925 If it is a string, pushes **0**. 926 927**z** 928 929: Pushes the current depth of the stack (before execution of this command) 930 onto the stack. 931 932**y**_r_ 933 934: Pushes the current stack depth of the register *r* onto the main stack. 935 936 Because each register has a depth of **1** (with the value **0** in the top 937 item) when dc(1) starts, dc(1) requires that each register's stack must 938 always have at least one item; dc(1) will give an error and reset otherwise 939 (see the **RESET** section). This means that this command will never push 940 **0**. 941 942 This is a **non-portable extension**. 943 944## Arrays 945 946These commands manipulate arrays. 947 948**:**_r_ 949 950: Pops the top two values off of the stack. The second value will be stored in 951 the array *r* (see the **REGISTERS** section), indexed by the first value. 952 953**;**_r_ 954 955: Pops the value on top of the stack and uses it as an index into the array 956 *r*. The selected value is then pushed onto the stack. 957 958**Y**_r_ 959 960: Pushes the length of the array *r* onto the stack. 961 962 This is a **non-portable extension**. 963 964## Global Settings 965 966These commands retrieve global settings. These are the only commands that 967require multiple specific characters, and all of them begin with the letter 968**g**. Only the characters below are allowed after the character **g**; any 969other character produces a parse error (see the **ERRORS** section). 970 971**gl** 972 973: Pushes the line length set by **DC_LINE_LENGTH** (see the **ENVIRONMENT 974 VARIABLES** section) onto the stack. 975 976**gz** 977 978: Pushes **0** onto the stack if the leading zero setting has not been enabled 979 with the **-z** or **-\-leading-zeroes** options (see the **OPTIONS** 980 section), non-zero otherwise. 981 982# REGISTERS 983 984Registers are names that can store strings, numbers, and arrays. (Number/string 985registers do not interfere with array registers.) 986 987Each register is also its own stack, so the current register value is the top of 988the stack for the register. All registers, when first referenced, have one value 989(**0**) in their stack, and it is a runtime error to attempt to pop that item 990off of the register stack. 991 992In non-extended register mode, a register name is just the single character that 993follows any command that needs a register name. The only exceptions are: a 994newline (**'\\n'**) and a left bracket (**'['**); it is a parse error for a 995newline or a left bracket to be used as a register name. 996 997## Extended Register Mode 998 999Unlike most other dc(1) implentations, this dc(1) provides nearly unlimited 1000amounts of registers, if extended register mode is enabled. 1001 1002If extended register mode is enabled (**-x** or **-\-extended-register** 1003command-line arguments are given), then normal single character registers are 1004used *unless* the character immediately following a command that needs a 1005register name is a space (according to **isspace()**) and not a newline 1006(**'\\n'**). 1007 1008In that case, the register name is found according to the regex 1009**\[a-z\]\[a-z0-9\_\]\*** (like bc(1) identifiers), and it is a parse error if 1010the next non-space characters do not match that regex. 1011 1012# RESET 1013 1014When dc(1) encounters an error or a signal that it has a non-default handler 1015for, it resets. This means that several things happen. 1016 1017First, any macros that are executing are stopped and popped off the stack. 1018The behavior is not unlike that of exceptions in programming languages. Then 1019the execution point is set so that any code waiting to execute (after all 1020macros returned) is skipped. 1021 1022Thus, when dc(1) resets, it skips any remaining code waiting to be executed. 1023Then, if it is interactive mode, and the error was not a fatal error (see the 1024**EXIT STATUS** section), it asks for more input; otherwise, it exits with the 1025appropriate return code. 1026 1027# PERFORMANCE 1028 1029Most dc(1) implementations use **char** types to calculate the value of **1** 1030decimal digit at a time, but that can be slow. This dc(1) does something 1031different. 1032 1033It uses large integers to calculate more than **1** decimal digit at a time. If 1034built in a environment where **DC_LONG_BIT** (see the **LIMITS** section) is 1035**64**, then each integer has **9** decimal digits. If built in an environment 1036where **DC_LONG_BIT** is **32** then each integer has **4** decimal digits. This 1037value (the number of decimal digits per large integer) is called 1038**DC_BASE_DIGS**. 1039 1040In addition, this dc(1) uses an even larger integer for overflow checking. This 1041integer type depends on the value of **DC_LONG_BIT**, but is always at least 1042twice as large as the integer type used to store digits. 1043 1044# LIMITS 1045 1046The following are the limits on dc(1): 1047 1048**DC_LONG_BIT** 1049 1050: The number of bits in the **long** type in the environment where dc(1) was 1051 built. This determines how many decimal digits can be stored in a single 1052 large integer (see the **PERFORMANCE** section). 1053 1054**DC_BASE_DIGS** 1055 1056: The number of decimal digits per large integer (see the **PERFORMANCE** 1057 section). Depends on **DC_LONG_BIT**. 1058 1059**DC_BASE_POW** 1060 1061: The max decimal number that each large integer can store (see 1062 **DC_BASE_DIGS**) plus **1**. Depends on **DC_BASE_DIGS**. 1063 1064**DC_OVERFLOW_MAX** 1065 1066: The max number that the overflow type (see the **PERFORMANCE** section) can 1067 hold. Depends on **DC_LONG_BIT**. 1068 1069**DC_BASE_MAX** 1070 1071: The maximum output base. Set at **DC_BASE_POW**. 1072 1073**DC_DIM_MAX** 1074 1075: The maximum size of arrays. Set at **SIZE_MAX-1**. 1076 1077**DC_SCALE_MAX** 1078 1079: The maximum **scale**. Set at **DC_OVERFLOW_MAX-1**. 1080 1081**DC_STRING_MAX** 1082 1083: The maximum length of strings. Set at **DC_OVERFLOW_MAX-1**. 1084 1085**DC_NAME_MAX** 1086 1087: The maximum length of identifiers. Set at **DC_OVERFLOW_MAX-1**. 1088 1089**DC_NUM_MAX** 1090 1091: The maximum length of a number (in decimal digits), which includes digits 1092 after the decimal point. Set at **DC_OVERFLOW_MAX-1**. 1093 1094**DC_RAND_MAX** 1095 1096: The maximum integer (inclusive) returned by the **'** command, if dc(1). Set 1097 at **2\^DC_LONG_BIT-1**. 1098 1099Exponent 1100 1101: The maximum allowable exponent (positive or negative). Set at 1102 **DC_OVERFLOW_MAX**. 1103 1104Number of vars 1105 1106: The maximum number of vars/arrays. Set at **SIZE_MAX-1**. 1107 1108These limits are meant to be effectively non-existent; the limits are so large 1109(at least on 64-bit machines) that there should not be any point at which they 1110become a problem. In fact, memory should be exhausted before these limits should 1111be hit. 1112 1113# ENVIRONMENT VARIABLES 1114 1115dc(1) recognizes the following environment variables: 1116 1117**DC_ENV_ARGS** 1118 1119: This is another way to give command-line arguments to dc(1). They should be 1120 in the same format as all other command-line arguments. These are always 1121 processed first, so any files given in **DC_ENV_ARGS** will be processed 1122 before arguments and files given on the command-line. This gives the user 1123 the ability to set up "standard" options and files to be used at every 1124 invocation. The most useful thing for such files to contain would be useful 1125 functions that the user might want every time dc(1) runs. Another use would 1126 be to use the **-e** option to set **scale** to a value other than **0**. 1127 1128 The code that parses **DC_ENV_ARGS** will correctly handle quoted arguments, 1129 but it does not understand escape sequences. For example, the string 1130 **"/home/gavin/some dc file.dc"** will be correctly parsed, but the string 1131 **"/home/gavin/some \"dc\" file.dc"** will include the backslashes. 1132 1133 The quote parsing will handle either kind of quotes, **'** or **"**. Thus, 1134 if you have a file with any number of single quotes in the name, you can use 1135 double quotes as the outside quotes, as in **"some 'dc' file.dc"**, and vice 1136 versa if you have a file with double quotes. However, handling a file with 1137 both kinds of quotes in **DC_ENV_ARGS** is not supported due to the 1138 complexity of the parsing, though such files are still supported on the 1139 command-line where the parsing is done by the shell. 1140 1141**DC_LINE_LENGTH** 1142 1143: If this environment variable exists and contains an integer that is greater 1144 than **1** and is less than **UINT16_MAX** (**2\^16-1**), dc(1) will output 1145 lines to that length, including the backslash newline combo. The default 1146 line length is **70**. 1147 1148 The special value of **0** will disable line length checking and print 1149 numbers without regard to line length and without backslashes and newlines. 1150 1151**DC_SIGINT_RESET** 1152 1153: If dc(1) is not in interactive mode (see the **INTERACTIVE MODE** section), 1154 then this environment variable has no effect because dc(1) exits on 1155 **SIGINT** when not in interactive mode. 1156 1157 However, when dc(1) is in interactive mode, then if this environment 1158 variable exists and contains an integer, a non-zero value makes dc(1) reset 1159 on **SIGINT**, rather than exit, and zero makes dc(1) exit. If this 1160 environment variable exists and is *not* an integer, then dc(1) will exit on 1161 **SIGINT**. 1162 1163 This environment variable overrides the default, which can be queried with 1164 the **-h** or **-\-help** options. 1165 1166**DC_TTY_MODE** 1167 1168: If TTY mode is *not* available (see the **TTY MODE** section), then this 1169 environment variable has no effect. 1170 1171 However, when TTY mode is available, then if this environment variable 1172 exists and contains an integer, then a non-zero value makes dc(1) use TTY 1173 mode, and zero makes dc(1) not use TTY mode. 1174 1175 This environment variable overrides the default, which can be queried with 1176 the **-h** or **-\-help** options. 1177 1178**DC_PROMPT** 1179 1180: If TTY mode is *not* available (see the **TTY MODE** section), then this 1181 environment variable has no effect. 1182 1183 However, when TTY mode is available, then if this environment variable 1184 exists and contains an integer, a non-zero value makes dc(1) use a prompt, 1185 and zero or a non-integer makes dc(1) not use a prompt. If this environment 1186 variable does not exist and **DC_TTY_MODE** does, then the value of the 1187 **DC_TTY_MODE** environment variable is used. 1188 1189 This environment variable and the **DC_TTY_MODE** environment variable 1190 override the default, which can be queried with the **-h** or **-\-help** 1191 options. 1192 1193# EXIT STATUS 1194 1195dc(1) returns the following exit statuses: 1196 1197**0** 1198 1199: No error. 1200 1201**1** 1202 1203: A math error occurred. This follows standard practice of using **1** for 1204 expected errors, since math errors will happen in the process of normal 1205 execution. 1206 1207 Math errors include divide by **0**, taking the square root of a negative 1208 number, using a negative number as a bound for the pseudo-random number 1209 generator, attempting to convert a negative number to a hardware integer, 1210 overflow when converting a number to a hardware integer, overflow when 1211 calculating the size of a number, and attempting to use a non-integer where 1212 an integer is required. 1213 1214 Converting to a hardware integer happens for the second operand of the power 1215 (**\^**), places (**\@**), left shift (**H**), and right shift (**h**) 1216 operators. 1217 1218**2** 1219 1220: A parse error occurred. 1221 1222 Parse errors include unexpected **EOF**, using an invalid character, failing 1223 to find the end of a string or comment, and using a token where it is 1224 invalid. 1225 1226**3** 1227 1228: A runtime error occurred. 1229 1230 Runtime errors include assigning an invalid number to any global (**ibase**, 1231 **obase**, or **scale**), giving a bad expression to a **read()** call, 1232 calling **read()** inside of a **read()** call, type errors (including 1233 attempting to execute a number), and attempting an operation when the stack 1234 has too few elements. 1235 1236**4** 1237 1238: A fatal error occurred. 1239 1240 Fatal errors include memory allocation errors, I/O errors, failing to open 1241 files, attempting to use files that do not have only ASCII characters (dc(1) 1242 only accepts ASCII characters), attempting to open a directory as a file, 1243 and giving invalid command-line options. 1244 1245The exit status **4** is special; when a fatal error occurs, dc(1) always exits 1246and returns **4**, no matter what mode dc(1) is in. 1247 1248The other statuses will only be returned when dc(1) is not in interactive mode 1249(see the **INTERACTIVE MODE** section), since dc(1) resets its state (see the 1250**RESET** section) and accepts more input when one of those errors occurs in 1251interactive mode. This is also the case when interactive mode is forced by the 1252**-i** flag or **-\-interactive** option. 1253 1254These exit statuses allow dc(1) to be used in shell scripting with error 1255checking, and its normal behavior can be forced by using the **-i** flag or 1256**-\-interactive** option. 1257 1258# INTERACTIVE MODE 1259 1260Like bc(1), dc(1) has an interactive mode and a non-interactive mode. 1261Interactive mode is turned on automatically when both **stdin** and **stdout** 1262are hooked to a terminal, but the **-i** flag and **-\-interactive** option can 1263turn it on in other situations. 1264 1265In interactive mode, dc(1) attempts to recover from errors (see the **RESET** 1266section), and in normal execution, flushes **stdout** as soon as execution is 1267done for the current input. dc(1) may also reset on **SIGINT** instead of exit, 1268depending on the contents of, or default for, the **DC_SIGINT_RESET** 1269environment variable (see the **ENVIRONMENT VARIABLES** section). 1270 1271# TTY MODE 1272 1273If **stdin**, **stdout**, and **stderr** are all connected to a TTY, then "TTY 1274mode" is considered to be available, and thus, dc(1) can turn on TTY mode, 1275subject to some settings. 1276 1277If there is the environment variable **DC_TTY_MODE** in the environment (see the 1278**ENVIRONMENT VARIABLES** section), then if that environment variable contains a 1279non-zero integer, dc(1) will turn on TTY mode when **stdin**, **stdout**, and 1280**stderr** are all connected to a TTY. If the **DC_TTY_MODE** environment 1281variable exists but is *not* a non-zero integer, then dc(1) will not turn TTY 1282mode on. 1283 1284If the environment variable **DC_TTY_MODE** does *not* exist, the default 1285setting is used. The default setting can be queried with the **-h** or 1286**-\-help** options. 1287 1288TTY mode is different from interactive mode because interactive mode is required 1289in the [bc(1) specification][1], and interactive mode requires only **stdin** 1290and **stdout** to be connected to a terminal. 1291 1292## Command-Line History 1293 1294Command-line history is only enabled if TTY mode is, i.e., that **stdin**, 1295**stdout**, and **stderr** are connected to a TTY and the **DC_TTY_MODE** 1296environment variable (see the **ENVIRONMENT VARIABLES** section) and its default 1297do not disable TTY mode. See the **COMMAND LINE HISTORY** section for more 1298information. 1299 1300## Prompt 1301 1302If TTY mode is available, then a prompt can be enabled. Like TTY mode itself, it 1303can be turned on or off with an environment variable: **DC_PROMPT** (see the 1304**ENVIRONMENT VARIABLES** section). 1305 1306If the environment variable **DC_PROMPT** exists and is a non-zero integer, then 1307the prompt is turned on when **stdin**, **stdout**, and **stderr** are connected 1308to a TTY and the **-P** and **-\-no-prompt** options were not used. The read 1309prompt will be turned on under the same conditions, except that the **-R** and 1310**-\-no-read-prompt** options must also not be used. 1311 1312However, if **DC_PROMPT** does not exist, the prompt can be enabled or disabled 1313with the **DC_TTY_MODE** environment variable, the **-P** and **-\-no-prompt** 1314options, and the **-R** and **-\-no-read-prompt** options. See the **ENVIRONMENT 1315VARIABLES** and **OPTIONS** sections for more details. 1316 1317# SIGNAL HANDLING 1318 1319Sending a **SIGINT** will cause dc(1) to do one of two things. 1320 1321If dc(1) is not in interactive mode (see the **INTERACTIVE MODE** section), or 1322the **DC_SIGINT_RESET** environment variable (see the **ENVIRONMENT VARIABLES** 1323section), or its default, is either not an integer or it is zero, dc(1) will 1324exit. 1325 1326However, if dc(1) is in interactive mode, and the **DC_SIGINT_RESET** or its 1327default is an integer and non-zero, then dc(1) will stop executing the current 1328input and reset (see the **RESET** section) upon receiving a **SIGINT**. 1329 1330Note that "current input" can mean one of two things. If dc(1) is processing 1331input from **stdin** in interactive mode, it will ask for more input. If dc(1) 1332is processing input from a file in interactive mode, it will stop processing the 1333file and start processing the next file, if one exists, or ask for input from 1334**stdin** if no other file exists. 1335 1336This means that if a **SIGINT** is sent to dc(1) as it is executing a file, it 1337can seem as though dc(1) did not respond to the signal since it will immediately 1338start executing the next file. This is by design; most files that users execute 1339when interacting with dc(1) have function definitions, which are quick to parse. 1340If a file takes a long time to execute, there may be a bug in that file. The 1341rest of the files could still be executed without problem, allowing the user to 1342continue. 1343 1344**SIGTERM** and **SIGQUIT** cause dc(1) to clean up and exit, and it uses the 1345default handler for all other signals. The one exception is **SIGHUP**; in that 1346case, and only when dc(1) is in TTY mode (see the **TTY MODE** section), a 1347**SIGHUP** will cause dc(1) to clean up and exit. 1348 1349# COMMAND LINE HISTORY 1350 1351dc(1) supports interactive command-line editing. 1352 1353If dc(1) can be in TTY mode (see the **TTY MODE** section), history can be 1354enabled. This means that command-line history can only be enabled when 1355**stdin**, **stdout**, and **stderr** are all connected to a TTY. 1356 1357Like TTY mode itself, it can be turned on or off with the environment variable 1358**DC_TTY_MODE** (see the **ENVIRONMENT VARIABLES** section). 1359 1360**Note**: tabs are converted to 8 spaces. 1361 1362# SEE ALSO 1363 1364bc(1) 1365 1366# STANDARDS 1367 1368The dc(1) utility operators are compliant with the operators in the bc(1) 1369[IEEE Std 1003.1-2017 (“POSIX.1-2017”)][1] specification. 1370 1371# BUGS 1372 1373None are known. Report bugs at https://git.yzena.com/gavin/bc. 1374 1375# AUTHOR 1376 1377Gavin D. Howard <gavin@yzena.com> and contributors. 1378 1379[1]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html 1380