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10 .TH BC 1 "Oct 25, 2017"
11 .SH NAME
12 bc \- arbitrary precision arithmetic language
13 .SH SYNOPSIS
14 .LP
15 .nf
16 \fB/usr/bin/bc\fR [\fB-c\fR] [\fB-l\fR] [\fIfile\fR]...
17 .fi
19 .SH DESCRIPTION
20 .sp
21 .LP
22 The \fBbc\fR utility implements an arbitrary precision calculator. It takes
23 input from any files given, then reads from the standard input. If the standard
24 input and standard output to \fBbc\fR are attached to a terminal, the
25 invocation of \fBbc\fR is \fIinteractive\fR, causing behavioral constraints
26 described in the following sections. \fBbc\fR processes a language that
27 resembles C and is a preprocessor for the desk calculator program \fBdc\fR,
28 which it invokes automatically unless the \fB-c\fR option is specified. In this
29 case the \fBdc\fR input is sent to the standard output instead.
30 .SH USAGE
31 .sp
32 .LP
33 The syntax for \fBbc\fR programs is as follows:
34 .sp
35 .ne 2
36 .na
37 \fB\fIL\fR\fR
38 .ad
39 .RS 5n
40 Means a letter \fBa\fR\(mi\fBz\fR,
41 .RE
43 .sp
44 .ne 2
45 .na
46 \fB\fIE\fR\fR
47 .ad
48 .RS 5n
49 Means an expression: a (mathematical or logical) value, an operand that takes
50 a value, or a combination of operands and operators that evaluates to a value,
51 .RE
53 .sp
54 .ne 2
55 .na
56 \fB\fIS\fR\fR
57 .ad
58 .RS 5n
59 Means a statement.
60 .RE
62 .SS "Comments"
63 .sp
64 .LP
65 Enclosed in \fB/*\fR and \fB*/\fR.
66 .SS "Names (Operands)"
67 .br
68 .in +2
69 Simple variables: \fIL\fR.
70 .in -2
71 .br
72 .in +2
73 Array elements: \fIL\fR [ \fIE\fR ] (up to \fBBC_DIM_MAX\fR dimensions).
74 .in -2
75 .br
76 .in +2
77 The words \fBibase\fR, \fBobase\fR (limited to \fBBC_BASE_MAX\fR), and
78 \fBscale\fR (limited to \fBBC_SCALE_MAX\fR).
79 .in -2
80 .SS "Other Operands"
81 .sp
82 .LP
83 Arbitrarily long numbers with optional sign and decimal point. Strings of fewer
84 than \fBBC_STRING_MAX\fR characters, between double quotes ("). \fB(\fR \fIE\fR
85 \fB)\fR
86 .sp
87 .ne 2
88 .na
89 \fB\fBsqrt ( \fR\fIE\fR\fB )\fR\fR
90 .ad
91 .RS 21n
92 Square root
93 .RE
95 .sp
96 .ne 2
97 .na
98 \fB\fBlength ( \fR\fIE\fR\fB )\fR\fR
99 .ad
100 .RS 21n
101 Number of significant decimal digits.
102 .RE
104 .sp
105 .ne 2
106 .na
107 \fB\fBscale ( \fR\fIE\fR\fB )\fR\fR
108 .ad
109 .RS 21n
110 Number of digits right of decimal point.
111 .RE
113 .sp
114 .ne 2
115 .na
116 \fB\fIL \fR\fB( \fR\fIE\fR , ... , \fIE\fR\fB )\fR\fR
117 .ad
118 .RS 21n
120 .RE
122 .SS "Operators"
123 .sp
124 .ne 2
125 .na
126 \fB\fB+ \(mi * / % ^\fR\fR
127 .ad
128 .sp .6
129 .RS 4n
130 (\fB%\fR is remainder; \fB^\fR is power)
131 .RE
133 .sp
134 .ne 2
135 .na
136 \fB\fB++ \(mi\(mi \fR\fR
137 .ad
138 .sp .6
139 .RS 4n
140 (prefix and postfix; apply to names)
141 .RE
143 .sp
144 .ne 2
145 .na
146 \fB\fB== <= >= != < >\fR\fR
147 .ad
148 .sp .6
149 .RS 4n
151 .RE
153 .sp
154 .ne 2
155 .na
156 \fB\fB= =+ =\(mi =* =/ =% =^\fR\fR
157 .ad
158 .sp .6
159 .RS 4n
161 .RE
163 .SS "Statements"
164 .br
165 .in +2
166 \fIE\fR
167 .in -2
168 .br
169 .in +2
170 \fB{\fR \fIS\fR \fB;\fR.\|.\|. \fB;\fR \fIS\fR \fB}\fR
171 .in -2
172 .br
173 .in +2
174 \fBif (\fR \fIE\fR \fB)\fR \fIS\fR
175 .in -2
176 .br
177 .in +2
178 \fBwhile (\fR \fIE\fR \fB)\fR \fIS\fR
179 .in -2
180 .br
181 .in +2
182 \fBfor (\fR \fIE\fR \fB;\fR \fIE\fR \fB;\fR \fIE\fR \fB)\fR \fIS\fR
183 .in -2
184 .br
185 .in +2
186 null statement
187 .in -2
188 .br
189 .in +2
190 \fBbreak\fR
191 .in -2
192 .br
193 .in +2
194 \fBquit\fR
195 .in -2
196 .sp
197 .LP
198 \&.string
199 .SS "Function Definitions"
200 .br
201 .in +2
202 \fBdefine\fR \fIL\fR \fB(\fR \fIL\fR \fB,\fR.\|.\|.\|\fB,\fR \fIL\fR \fB) {\fR
203 .in -2
204 .br
205 .in +2
206 \fBauto\fR \fIL\fR \fB,\fR.\|.\|.\|\fB,\fR \fIL\fR
207 .in -2
208 .br
209 .in +2
210 \fIS\fR \fB;\fR.\|.\|.\| \fIS\fR
211 .in -2
212 .br
213 .in +2
214 \fBreturn (\fR \fIE\fR \fB)\fR
215 .in -2
216 .br
217 .in +2
218 \fB}\fR
219 .in -2
220 .SS "Functions in \fB-l\fR Math Library"
221 .sp
222 .ne 2
223 .na
224 \fB\fBs(\fR\fIx\fR\fB)\fR\fR
225 .ad
226 .RS 10n
227 sine
228 .RE
230 .sp
231 .ne 2
232 .na
233 \fB\fBc(\fR\fIx\fR\fB)\fR\fR
234 .ad
235 .RS 10n
236 cosine
237 .RE
239 .sp
240 .ne 2
241 .na
242 \fB\fBe(\fR\fIx\fR\fB)\fR\fR
243 .ad
244 .RS 10n
245 exponential
246 .RE
248 .sp
249 .ne 2
250 .na
251 \fB\fBl(\fR\fIx\fR\fB)\fR\fR
252 .ad
253 .RS 10n
254 log
255 .RE
257 .sp
258 .ne 2
259 .na
260 \fB\fBa(\fR\fIx\fR\fB)\fR\fR
261 .ad
262 .RS 10n
263 arctangent
264 .RE
266 .sp
267 .ne 2
268 .na
269 \fB\fBj(\fR\fIn\fR\fB,\fR\fIx)\fR\fR
270 .ad
271 .RS 10n
272 Bessel function
273 .RE
275 .sp
276 .LP
277 All function arguments are passed by value.
278 .sp
279 .LP
280 The value of a statement that is an expression is printed unless the main
281 operator is an assignment. Either semicolons or new-lines may separate
282 statements. Assignment to \fBscale\fR influences the number of digits to be
283 retained on arithmetic operations in the manner of \fBdc\fR. Assignments to
284 \fBibase\fR or \fBobase\fR set the input and output number radix respectively.
285 .sp
286 .LP
287 The same letter may be used as an array, a function, and a simple variable
288 simultaneously. All variables are global to the program. \fBauto\fR variables
289 are stacked during function calls. When using arrays as function arguments or
290 defining them as automatic variables, empty square brackets must follow the
291 array name.
292 .SH OPTIONS
293 .sp
294 .LP
295 The following operands are supported:
296 .sp
297 .ne 2
298 .na
299 \fB\fB-c\fR\fR
300 .ad
301 .RS 6n
302 Compiles only. The output is \fBdc\fR commands that are sent to the standard
303 output.
304 .RE
306 .sp
307 .ne 2
308 .na
309 \fB\fB-l\fR\fR
310 .ad
311 .RS 6n
312 Defines the math functions and initializes \fBscale\fR to \fB20\fR, instead of
313 the default zero. All math results have the scale of \fB20\fR.
314 .RE
316 .SH OPERANDS
317 .sp
318 .LP
319 The following operands are supported:
320 .sp
321 .ne 2
322 .na
323 \fB\fIfile\fR\fR
324 .ad
325 .RS 8n
326 A pathname of a text file containing \fBbc\fR program statements. After all
327 cases of \fIfile\fR have been read, \fBbc\fR reads the standard input.
328 .RE
330 .SH EXAMPLES
331 .LP
332 \fBExample 1 \fRSetting the precision of a variable
333 .sp
334 .LP
335 In the shell, the following assigns an approximation of the first ten digits of
336 \fBn\fR to the variable \fIx\fR:
338 .sp
339 .in +2
340 .nf
341 \fBx=$(printf "%s\en" 'scale = 10; 104348/33215' | bc)\fR
342 .fi
343 .in -2
344 .sp
346 .LP
347 \fBExample 2 \fRDefining a computing function
348 .sp
349 .LP
350 Defines a function to compute an approximate value of the exponential function:
352 .sp
353 .in +2
354 .nf
355 \fBscale = 20
356 define e(x){
357 auto a, b, c, i, s
358 a = 1
359 b = 1
360 s = 1
361 for(i=1; 1==1; i++){
362 a = a*x
363 b = b*i
364 c = a/b
365 if(c == 0) return(s)
366 s = s+c
367 }
368 }\fR
369 .fi
370 .in -2
371 .sp
373 .LP
374 \fBExample 3 \fRPrinting the approximate values of the function
375 .sp
376 .LP
377 Prints approximate values of the exponential function of the first ten
378 integers:
380 .sp
381 .in +2
382 .nf
383 \fBfor(i=1; i<=10; i++) e(i)\fR
384 .fi
385 .in -2
386 .sp
388 .sp
389 .LP
390 or
392 .sp
393 .in +2
394 .nf
395 \fBfor (i = 1; i <= 10; ++i) { e(i) }\fR
396 .fi
397 .in -2
398 .sp
400 .SH ENVIRONMENT VARIABLES
401 .sp
402 .LP
403 See \fBenviron\fR(5) for descriptions of the following environment variables
404 that affect the execution of \fBbc\fR: \fBLANG\fR, \fBLC_ALL\fR,
405 \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
406 .SH EXIT STATUS
407 .sp
408 .LP
409 The following exit values are returned:
410 .sp
411 .ne 2
412 .na
413 \fB\fB0\fR\fR
414 .ad
415 .RS 15n
416 All input files were processed successfully.
417 .RE
419 .sp
420 .ne 2
421 .na
422 \fB\fBunspecified\fR\fR
423 .ad
424 .RS 15n
425 An error occurred.
426 .RE
428 .SH FILES
429 .sp
430 .ne 2
431 .na
432 \fB\fB/usr/lib/lib.b\fR\fR
433 .ad
434 .RS 25n
435 mathematical library
436 .RE
438 .sp
439 .ne 2
440 .na
441 \fB\fB/usr/include/limits.h\fR\fR
442 .ad
443 .RS 25n
444 to define BC_ parameters
445 .RE
447 .SH ATTRIBUTES
448 .sp
449 .LP
450 See \fBattributes\fR(5) for descriptions of the following attributes:
451 .sp
453 .sp
454 .TS
455 box;
456 c | c
457 l | l .
458 ATTRIBUTE TYPE ATTRIBUTE VALUE
459 _
460 Interface Stability Standard
461 .TE
463 .SH SEE ALSO
464 .sp
465 .LP
466 \fBdc\fR(1), \fBawk\fR(1), \fBattributes\fR(5), \fBenviron\fR(5),
467 \fBstandards\fR(5)
468 .SH NOTES
469 .sp
470 .LP
471 The \fBbc\fR command does not recognize the logical operators \fB&&\fR and
472 \fB|\||\fR.
473 .sp
474 .LP
475 The \fBfor\fR statement must have all three expressions (\fIE\fR's).