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.\" bc.1 - the *roff document processor source for the bc manual
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.\" This file is part of GNU bc.
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.\" Copyright (C) 1991-1994, 1997, 2000 Free Software Foundation, Inc.
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.\" Copyright (C) 1991-1994, 1997, 2000, 2003, 2006 Free Software Foundation, Inc.
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.\" This program is free software; you can redistribute it and/or modify
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.\" it under the terms of the GNU General Public License as published by
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.\" You should have received a copy of the GNU General Public License
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.\" along with this program; see the file COPYING. If not, write to:
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.\" The Free Software Foundation, Inc.
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.\" 59 Temple Place, Suite 330
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.\" Boston, MA 02111 USA
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.\" 51 Franklin Street, Fifth Floor
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.\" Boston, MA 02110-1301 USA
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.\" You may contact the author by:
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.\" e-mail: philnelson@acm.org
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the "var" part is evaluated only once. This can make a difference if
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"var" is an array.
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Relational expressions are a special kind of expression
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Relational expressions are a special kind of expression
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that always evaluate to 0 or 1, 0 if the relation is false and 1 if
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the relation is true. These may appear in any legal expression.
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(POSIX bc requires that relational expressions are used only in if,
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Parameters are numbers or arrays (an extension). In the function definition,
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zero or more parameters are defined by listing their names separated by
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commas. Numbers are only call by value parameters. Arrays are only
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call by variable. Arrays are specified in the parameter definition by
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commas. All parameters are call by value parameters.
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Arrays are specified in the parameter definition by
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the notation "\fIname\fB[]\fR". In the function call, actual parameters
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are full expressions for number parameters. The same notation is used
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for passing arrays as for defining array parameters. The named array is
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passed by variable to the function. Since function definitions are dynamic,
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passed by value to the function. Since function definitions are dynamic,
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parameter numbers and types are checked when a function is called. Any
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mismatch in number or types of parameters will cause a runtime error.
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A runtime error will also occur for the call to an undefined function.
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standard function \fBread\fR, which will always use the current value
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of \fBibase\fR for conversion of numbers.
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As an extension, the format of the definition has been slightly relaxed.
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The standard requires the opening brace be on the same line as the
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\fBdefine\fR keyword and all other parts must be on following lines.
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This version of \fBbc\fR will allow any number of newlines before and
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after the opening brace of the function. For example, the following
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definitions are legal.
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Several extensions have been added to functions. First, the format of
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the definition has been slightly relaxed. The standard requires the
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opening brace be on the same line as the \fBdefine\fR keyword and all
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other parts must be on following lines. This version of \fBbc\fR will
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allow any number of newlines before and after the opening brace of the
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function. For example, the following definitions are legal.
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Functions may be defined as \fBvoid\fR. A void
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funtion returns no value and thus may not be used in any place that needs
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a value. A void function does not produce any output when called by itself
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on an input line. The key word \fBvoid\fR is placed between the key word
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\fBdefine\fR and the function name. For example, consider the following
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define py (y) { print "--->", y, "<---", "\n"; }
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define void px (x) { print "--->", x, "<---", "\n"; }
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Since \fBpy\fR is not a void function, the call of \fBpy(1)\fR prints
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the desired output and then prints a second line that is the value of
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the function. Since the value of a function that is not given an
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explicit return statement is zero, the zero is printed. For \fBpx(1)\fR,
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no zero is printed because the function is a void function.
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Also, call by variable for arrays was added. To declare
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a call by variable array, the declaration of the array parameter in the
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function definition looks like "\fI*name\fB[]\fR". The call to the
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function remains the same as call by value arrays.
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If \fBbc\fR is invoked with the \fB-l\fR option, a math library is preloaded
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and the default scale is set to 20. The math functions will calculate their
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.IP "e (\fIx\fR)"
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The exponential function of raising e to the value x.
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.IP "j (\fIn,x\fR)"
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The bessel function of integer order n of x.
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The Bessel function of integer order n of x.
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In /bin/sh, the following will assign the value of "pi" to the shell
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variable \fBpi\fR.
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extensions, where a feature is extended to add more functionality and
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additions, where new features are added.
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The following is the list of differences and extensions.
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.IP "LANG environment"
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This version does not conform to the POSIX standard in the processing
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of the LANG environment variable and all environment variables starting
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Traditional and POSIX
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have single letter names for functions, variables and arrays. They have
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been extended to be multi-character names that start with a letter and
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may contain letters, numbers and the underscore character.
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Strings are not allowed to contain NUL characters. POSIX says all characters
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must be included in strings.
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POSIX \fBbc\fR does not have a \fBlast\fR variable. Some implementations
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of \fBbc\fR use the period (.) in a similar way.
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POSIX \fBbc\fR allows comparisons only in the if statement, the while
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statement, and the second expression of the for statement. Also, only
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one relational operation is allowed in each of those statements.
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processor. Some of them may have been changed by an installation.
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Use the limits statement to see the actual values.
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The maximum output base is currently set at 999. The maximum input base
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This is currently an arbitrary limit of 65535 as distributed. Your
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installation may be different.
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The number of digits after the decimal point is limited to INT_MAX digits.
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Also, the number of digits before the decimal point is limited to INT_MAX
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The limit on the number of characters in a string is INT_MAX characters.
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The value of the exponent in the raise operation (^) is limited to LONG_MAX.
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.IP "variable names"
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The current limit on the number of unique names is 32767 for each of
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.IP "BC_ENV_ARGS"
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This is another mechanism to get arguments to \fBbc\fR. The
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format is the same as the command line arguments. These arguments
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are processed first, so any files listed in the environent arguments
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are processed first, so any files listed in the environment arguments
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are processed before any command line argument files. This allows
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the user to set up "standard" options and files to be processed
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at every invocation of \fBbc\fR. The files in the environment
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variables would typically contain function definitions for functions
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the user wants defined every time \fBbc\fR is run.
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.IP "BC_LINE_LENGTH"
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This should be an integer specifing the number of characters in an
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This should be an integer specifying the number of characters in an
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output line for numbers. This includes the backslash and newline characters
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for long numbers. As an extension, the value of zero disables the
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multi-line feature. Any other value of this variable that is less than
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3 sets the line length to 70.
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If any file on the command line can not be opened, \fBbc\fR will report
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that the file is unavailable and terminate. Also, there are compile
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removed
doc/bc.1
