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.TH BC 1 "Aug 29, 2003"
.SH NAME
bc \- arbitrary precision arithmetic language
.SH SYNOPSIS
.nf
\fB/usr/bin/bc\fR [\fB-c\fR] [\fB-l\fR] [\fIfile\fR]...
.fi

.LP
.nf
\fB/usr/xpg6/bin/bc\fR [\fB-c\fR] [\fB-l\fR] [\fIfile\fR]...
.fi

.SH DESCRIPTION
The \fBbc\fR utility implements an arbitrary precision calculator. It takes
input from any files given, then reads from the standard input. If the standard
input and standard output to \fBbc\fR are attached to a terminal, the
invocation of \fBbc\fR is  \fIinteractive\fR, causing behavioral constraints
described in the following sections. \fBbc\fR processes a language that
resembles C and is a preprocessor for the desk calculator program \fBdc\fR,
which it invokes automatically unless the \fB-c\fR option is specified. In this
case the \fBdc\fR input is sent to the standard output instead.
.SH USAGE
The syntax for  \fBbc\fR programs is as follows:
.sp
.ne 2
.na
\fB\fIL\fR\fR
.ad
.RS 5n
Means a letter \fBa\fR\(mi\fBz\fR,
.RE

.sp
.ne 2
.na
\fB\fIE\fR\fR
.ad
.RS 5n
Means an expression: a (mathematical or logical) value, an operand  that takes
a value, or a combination of operands and operators that evaluates to a value,
.RE

.sp
.ne 2
.na
\fB\fIS\fR\fR
.ad
.RS 5n
Means a statement.
.RE

.SS "Comments"
Enclosed in \fB/*\fR and \fB*/\fR.
.SS "Names (Operands)"
.in +2
Simple variables: \fIL\fR.
.in -2
.br
.in +2
Array elements: \fIL\fR [ \fIE\fR ] (up to \fBBC_DIM_MAX\fR dimensions).
.in -2
.br
.in +2
The words \fBibase\fR, \fBobase\fR (limited to \fBBC_BASE_MAX\fR), and
\fBscale\fR (limited to \fBBC_SCALE_MAX\fR).
.in -2
.SS "Other Operands"
Arbitrarily long numbers with optional sign and decimal point. Strings of fewer
than \fBBC_STRING_MAX\fR characters, between double quotes ("). \fB(\fR \fIE\fR
\fB)\fR
.sp
.ne 2
.na
\fB\fBsqrt ( \fR\fIE\fR\fB )\fR\fR
.ad
.RS 21n
Square root
.RE

.sp
.ne 2
.na
\fB\fBlength ( \fR\fIE\fR\fB )\fR\fR
.ad
.RS 21n
Number of significant decimal digits.
.RE

.sp
.ne 2
.na
\fB\fBscale ( \fR\fIE\fR\fB )\fR\fR
.ad
.RS 21n
Number of digits right of decimal point.
.RE

.sp
.ne 2
.na
\fB\fIL \fR\fB( \fR\fIE\fR , ... , \fIE\fR\fB )\fR\fR
.ad
.RS 21n

.RE

.SS "Operators"
.ne 2
.na
\fB\fB+   \(mi   *   /   %   ^\fR\fR
.ad
.sp .6
.RS 4n
(\fB%\fR is remainder; \fB^\fR is power)
.RE

.sp
.ne 2
.na
\fB\fB++   \(mi\(mi \fR\fR
.ad
.sp .6
.RS 4n
(prefix and postfix; apply to names)
.RE

.sp
.ne 2
.na
\fB\fB==   <=   >=   !=   <   >\fR\fR
.ad
.sp .6
.RS 4n

.RE

.sp
.ne 2
.na
\fB\fB=   =+   =\(mi   =*   =/   =%   =^\fR\fR
.ad
.sp .6
.RS 4n

.RE

.SS "Statements"
.in +2
\fIE\fR
.in -2
.br
.in +2
\fB{\fR \fIS\fR \fB;\fR.\|.\|. \fB;\fR \fIS\fR \fB}\fR
.in -2
.br
.in +2
\fBif (\fR \fIE\fR \fB)\fR \fIS\fR
.in -2
.br
.in +2
\fBwhile (\fR \fIE\fR \fB)\fR \fIS\fR
.in -2
.br
.in +2
\fBfor (\fR \fIE\fR \fB;\fR \fIE\fR \fB;\fR \fIE\fR \fB)\fR \fIS\fR
.in -2
.br
.in +2
null statement
.in -2
.br
.in +2
\fBbreak\fR
.in -2
.br
.in +2
\fBquit\fR
.in -2
.sp
.LP
\&.string
.SS "Function Definitions"
.in +2
\fBdefine\fR \fIL\fR \fB(\fR \fIL\fR \fB,\fR.\|.\|.\|\fB,\fR \fIL\fR \fB) {\fR
.in -2
.br
.in +2
\fBauto\fR \fIL\fR \fB,\fR.\|.\|.\|\fB,\fR \fIL\fR
.in -2
.br
.in +2
\fIS\fR \fB;\fR.\|.\|.\| \fIS\fR
.in -2
.br
.in +2
\fBreturn (\fR \fIE\fR \fB)\fR
.in -2
.br
.in +2
\fB}\fR
.in -2
.SS "Functions in \fB-l\fR Math Library"
.ne 2
.na
\fB\fBs(\fR\fIx\fR\fB)\fR\fR
.ad
.RS 10n
sine
.RE

.sp
.ne 2
.na
\fB\fBc(\fR\fIx\fR\fB)\fR\fR
.ad
.RS 10n
cosine
.RE

.sp
.ne 2
.na
\fB\fBe(\fR\fIx\fR\fB)\fR\fR
.ad
.RS 10n
exponential
.RE

.sp
.ne 2
.na
\fB\fBl(\fR\fIx\fR\fB)\fR\fR
.ad
.RS 10n
log
.RE

.sp
.ne 2
.na
\fB\fBa(\fR\fIx\fR\fB)\fR\fR
.ad
.RS 10n
arctangent
.RE

.sp
.ne 2
.na
\fB\fBj(\fR\fIn\fR\fB,\fR\fIx)\fR\fR
.ad
.RS 10n
Bessel function
.RE

.sp
.LP
All function arguments are passed by value.
.sp
.LP
The value of a statement that is an expression is printed unless the main
operator is an assignment. Either semicolons or new-lines may separate
statements. Assignment to \fBscale\fR influences the number of digits to be
retained on arithmetic operations in the manner of \fBdc\fR. Assignments to
\fBibase\fR or \fBobase\fR set the input and output number radix respectively.
.sp
.LP
The same letter may be used as an array, a function, and a simple variable
simultaneously. All variables are global to the program. \fBauto\fR variables
are stacked during function calls. When using arrays as function arguments or
defining them as automatic variables, empty square brackets must follow the
array name.
.SH OPTIONS
The following operands are supported:
.sp
.ne 2
.na
\fB\fB-c\fR\fR
.ad
.RS 6n
Compiles only. The output is \fBdc\fR commands that are sent to the standard
output.
.RE

.SS "/usr/bin/bc"
.ne 2
.na
\fB\fB-l\fR\fR
.ad
.RS 6n
Defines the math functions and initializes \fBscale\fR to \fB20\fR, instead of
the default zero.
.RE

.SS "/usr/xpg6/bin/bc"
.ne 2
.na
\fB\fB-l\fR\fR
.ad
.RS 6n
Defines the math functions and initializes \fBscale\fR to \fB20\fR, instead of
the default zero. All math results have the scale of \fB20\fR.
.RE

.SH OPERANDS
The following operands are supported:
.sp
.ne 2
.na
\fB\fIfile\fR\fR
.ad
.RS 8n
A pathname of a text file containing \fBbc\fR program statements. After all
cases of \fIfile\fR have been read, \fBbc\fR reads the standard input.
.RE

.SH EXAMPLES
\fBExample 1 \fRSetting the precision of a variable
.sp
.LP
In the shell, the following assigns an approximation of the first ten digits of
\fBn\fR to the variable \fIx\fR:

.sp
.in +2
.nf
\fBx=$(printf "%s\en" 'scale = 10; 104348/33215' | bc)\fR
.fi
.in -2
.sp

.LP
\fBExample 2 \fRDefining a computing function
.sp
.LP
Defines a function to compute an approximate value of the exponential function:

.sp
.in +2
.nf
\fBscale = 20
define e(x){
	auto a, b, c, i, s
	a = 1
	b = 1
	s = 1
	for(i=1; 1==1; i++){
		a = a*x
		b = b*i
		c = a/b
		if(c == 0) return(s)
		s = s+c
	}
}\fR
.fi
.in -2
.sp

.LP
\fBExample 3 \fRPrinting the approximate values of the function
.sp
.LP
Prints approximate values of the exponential function of the first ten
integers:

.sp
.in +2
.nf
\fBfor(i=1; i<=10; i++) e(i)\fR
.fi
.in -2
.sp

.sp
.LP
or

.sp
.in +2
.nf
\fBfor (i = 1; i <= 10; ++i) {         e(i) }\fR
.fi
.in -2
.sp

.SH ENVIRONMENT VARIABLES
See \fBenviron\fR(7) for descriptions of the following environment variables
that affect the execution of \fBbc\fR: \fBLANG\fR, \fBLC_ALL\fR,
\fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
.SH EXIT STATUS
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 15n
All input files were processed successfully.
.RE

.sp
.ne 2
.na
\fB\fBunspecified\fR\fR
.ad
.RS 15n
An error occurred.
.RE

.SH FILES
.ne 2
.na
\fB\fB/usr/lib/lib.b\fR\fR
.ad
.RS 25n
mathematical library
.RE

.sp
.ne 2
.na
\fB\fB/usr/include/limits.h\fR\fR
.ad
.RS 25n
to define BC_ parameters
.RE

.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.BR awk (1),
.BR dc (1),
.BR attributes (7),
.BR environ (7),
.BR standards (7)
.SH NOTES
The \fBbc\fR command does not recognize the logical operators \fB&&\fR and
\fB|\||\fR.
.sp
.LP
The \fBfor\fR statement must have all three expressions (\fIE\fR's).